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Quantified dermal activity data from a four-child pilot field study
Abstract
Thirty-three hours of videotape collected in a 1993 pilot study were quantified, via a video translation software application, to obtain left and right hand activity data of four children of farmworkers. Reported here are the children's contact duration and frequency for each object in their environment, duration spent in each location and activity exertion level, and frequency distributions of object contact durations. The pilot study provided valuable information for evaluating and improving videotaping and videotape translation methodologies as a means of gathering activity information that can be used to refine dermal exposure estimates. Although a larger database of children's videotaped activities for different ages and populations is needed before generalizations can be made, the data presented here are the most detailed information to date for children's micro-level dermal activities.
... A child's hands are the means for placing food in the mouth and are the immediate source of nondietary exposure through hand-to-mouth and object-tomouth behavior. Because the hand is used to act on the environment and probably has more contact with water, soil, and dust than any other part of the body, hands have been used as the equivalent of dermal surfaces in several studies (14)(15)(16). ...
... Observers then replayed the videotapes and recorded the frequency of object-to-mouth contact, hand-to-mouth contact, and hand (14) 0.6 (10) 0.7 (7) 0.9 (17) 0.6 (10) 0.6 (10) TV, television. ...
... Objects recorded included clothing, dirt, another hand, mouth, object, other items, smooth surfaces, and textured surfaces. Zartarian et al. (14,93) reported results for the left hand, right hand, and mouth from a videotape study of four children in an agricultural setting (2-4 years of age) in California (31 hr of videotape). This study used a computer software application (94) rather than a scorecard to obtain the sequence of a wide array of objects contacted and the duration of each contact. ...
... While many studies have focused on sources and transport of pesticides, health effects, and even dose, human exposure assessment is still poorly understood. From defining exposure to estimates of uncertainty and accuracy, exposure has historically been the most controversial and least studied component of the risk model (Zartarian, et al., 1997). It seems appropriate then that scientists and researchers focus their efforts on methods of exposure measurement and prediction. ...
... For some scenarios, such as measuring residential dermal exposures of children or collecting real-time personal inhalation exposures for a large population, however, the direct approach of exposure assessment may be infeasible. It may be burdensome to obtain chemical concentrations from mobile sources, children may not tolerate personal monitors or patches, and monitoring a statistically representative group would likely be expensive (Duan, 1982; Zartarian et al., 1997; Ott, 1990; Klepeis, 1999). The alternative is an indirect approach where human activities or time allocations are collected separately from environmental data in particular media and/or microenvironments. ...
... Assessing risks due to exposure has traditionally focused on a single pathway 1) numerical inputs to the equation can be determined from relevant activity pattern fields 2) equations for different routes are at a consistent level of detail 3) relevant data can be linked across routes 4) equations comply with exposure definitions developed by Zartarian et al., 1997 5) inputs can be obtained from available, measurable data ...
Submitted to the Department of Civil and Environmental Engineering. Copyright by the author. Thesis (Ph. D.)--Stanford University, 2004.
... Approximately 93 hours (2-6 hours per child) of videotape were obtained from 23 children during the summers of 2001 and 2002. While previous studies were performed to gather micro-activity data (Akland et al., 2000;AuYeung et al., 2004AuYeung et al., , 2006Black et al., 2005;Brinkman et al., 1999;Freeman et al., 2001Freeman et al., , 2005Reed et al., 1999;Tulve et al., 2002;Zartarian et al., 1995Zartarian et al., , 1997aZartarian et al., , 1997bZartarian et al., , 1998, analysis of duration in microenvironments, and frequencies and durations of contact events in this study will aid understanding of how children interact with their environment at different developmental stages (i.e., infants and toddlers). This study also expands available activity pattern data on farmworker children, who may be particularly vulnerable to pesticide exposure (Zartarian et al., 1995). ...
... The object grid contained 34 object/surface categories and categories designating when there is no contact with a surface ("Nothing") and when the child's body part is not visible by the researcher ("Not in View"). The object designations were selected based on experience from previous studies (AuYeung et al., 2004(AuYeung et al., ,2006Ferguson et al., 2005;Zartarian et al., 1997bZartarian et al., , 1998. Nine "Object Purposes" were chosen (e.g., ground surfaces, walls/furniture, toys, etc.), and surface types were matched to the "Object Purposes" (e.g., rock/brick, wood, plastic). ...
... The current study confirms some observations from the pilot study (Zartarian et al., 1997b(Zartarian et al., , 1998. For example, children's mouth and hand contacts exhibit short durations and high frequencies (Zartarian et al., 1997b). ...
This study was conducted to describe exposure prone behaviors of infants and toddlers in the farmworker community. Analysis of hand and mouth contact frequencies and durations aids understanding of how children interact with their environment and are exposed via contact with surfaces. All 23 participating children (8 female infants, 5 male infants, 5 female toddlers and 5 male toddlers) lived with at least one farmworker. Children were videotaped at home for 2-6 h. Video footage was translated into micro-level activity time series (MLATS) for both hands and the mouth. MLATS were processed to calculate hourly duration in microenvironments, contact frequency, hourly contact duration and median contact duration. The median hourly duration spent indoors was 53 min/h. The median hand-to-mouth frequency was 15.2 events/h and the median object-to-mouth frequency was 27.2 events/h. The hourly mouthing duration was 1.2 and 2.2 min/h with the hands and objects, respectively. The median mouthing duration with hands and objects was 2 s. The median contact frequency for both hands combined was 689.4 events/h with an hourly contact duration of 100.5 min/h and a median contact duration of 3s. Infants had higher mouthing frequencies with non-dietary objects while toddlers had higher mouthing frequencies with objects associated with pica (i.e., paper). Boys had higher contact frequencies while girls had longer contact durations. These sub-group differences indicate factors such as age and gender should be accounted for when conducting exposure assessments. Contact frequencies in this study are higher than current US EPA recommendations, questioning their protective value for infants and toddlers.
... This approach serves both as a means of validating information available from questionnaires, and as a direct measure of frequency of contact with different types of surfaces and hand-to-mouth behaviors. Recently, a study employed a videotaping methodology to quantify the hand and mouthing activities of four children (Zartarian et al., 1995Zartarian et al., , 1997). The research reported here significantly expands upon the study conducted by Zartarian by utilizing a videotaping methodology in parallel with a time/activity questionnaire to quantify the hand and mouthing behaviors of 30 children and evaluate parents' perception of their children's activities. ...
... However, object-to-mouth behavior showed a strong preference for the right hand compared to the left hand for nearly all children (mean ratio of right-to-left object-to-mouth behaviors=6.8). Because similar work has been conducted and results published concerning children's hand and mouthing behaviors , frequency counts from our study were compared to values reported by Zartarian et al. (1997). To compare frequency counts of activities found in the Zartarian study with frequency counts obtained in the current study, several variables from the Zartarian study were condensed to correspond to scores obtained for our broader categories. ...
... To compare frequency counts of activities found in the Zartarian study with frequency counts obtained in the current study, several variables from the Zartarian study were condensed to correspond to scores obtained for our broader categories. Average values based on means across the four children investigated in the study of Zartarian et al. (1997) were calculated for each activity and compared to the average values obtained in this study. Frequency scores for seven activities measured in the two studies are illustrated inFigure 3, and frequency counts are very similar for contacts with dirt, the mouth, other items, and hard surfaces. ...
A videotaping methodology has been developed for use in quantifying the types and frequencies of children's hand and mouthing activities that could lead to exposure to environmental pollutants via dermal and ingestion pathways. Twenty children in day care, ages 3-6 years and 10 children in residences, ages 2-5 years, were videotaped during their waking hours for 1 day. Parents of each child completed questionnaires for the purpose of evaluating the accuracy of parental reports of hand-to-mouth rates. Videotapes were translated as quantifiable activities by two trained observers whose reporting reliability was checked throughout the investigation. Results determined that reliability of the videotaping method was very good, even over a year post-training. From videotape data, the average hand-to-mouth frequency rate was determined to be 9.5 contacts/h. These values are considerably higher than the current default value of 1.56 contacts/h under consideration by the EPA.
... The videotranslation component involves the use of a computer software program to maintain the sequential pattern of activity and allow for second time intervals. Zartarian et al. (1995Zartarian et al. ( , 1997, by utilizing 33 h of videotaped data for four young children, were able to refine the methodologies and summarized right, left-hand and mouth activity in terms of frequency and duration of contact, concluding that these methodologies are an essential means for the collection of activity details for dermal exposure. Videotaping and video translation methodologies were later used to study 23 young children of farmworkers and to assess exposures to pesticides through quantification of their micro-activity patterns [15,16]. ...
... Previous studies have demonstrated that the left hand is less active than the right hand for most young children. In addition, these studies also indicate that unless children are involved in a continuous eating event, the mouth is also less active [13][14][15][16][17][18][19]. The Mouth grid within the palette is only slightly different to the Left and Right-Hand grid and includes contact with hands. ...
In a study to evaluate beach play activities, 120 children were videotaped to observe and quantify factors that could influence their exposure to contaminants in the beach environment. Children aged 1 to 6 years were followed by researchers with video cameras at beaches (two in Miami, Florida and two in Galveston, Texas) for approximately one hour each. Factors evaluated included time spent in various beach locations, various activities engaged in, and various surfaces contacted (including contacts by hand and mouth). Activities recorded in the videos were transcribed to text files to allow for quantitative analyses. Across all sexes, age groups, and beaches, Wading was the most common activity and Seawater was the most common location where children played. The left hand was found to not be in contact with objects most of the time, while the right hand, considered the most dominant hand in most cases, contacted Plastic-Toys the most. Although activity patterns collection through videotaping and videotranslation can be labor-intensive, once collected, they can be widely useful for estimates of exposures to all contaminants in the beach environment (e.g., microorganisms and chemicals) as well as UV exposure, with considerations for whether the contaminants are found in water, sand or both. These activity patterns were collected to potentially look at exposures following the Deepwater Horizon 2010 Spill.
... Different ages from 6 months old to adulthood were chosen based on published studies suggesting that children beginning as young as 6 months are exposed due to hand-to-mouth and/ or object-to-mouth contacts (Freeman et al., 2005;Reed et al., 1999;Tulve et al., 2002;Xue et al., 2007;Zartarian et al., 1997). ...
... Exposure of young children, for whom indirect ingestion of residues from object-and hand-to-mouth activities is common, is subject to the highest levels of pyrethroids. Published studies have suggested that young children (2-5 years) exhibit higher hand-to-mouth and/or object-to-mouth contacts than older children and adults (Freeman et al., 2005;Reed et al., 1999;Tulve et al., 2002;Xue et al., 2007;Zartarian et al., 1997). Such exposures to children below 6 months of age are negligible because they are less mobile and the levels of pyrethroids in food and drinking water are generally low (U.S. EPA, 2019). ...
The assessment of potentially sensitive populations is an important application of risk assessment. To address the concern for age-related sensitivity to pyrethroid insecticides, life-stage physiologically based pharmacokinetic (PBPK) modeling supported by in vitro to in vivo extrapolation (IVIVE) was conducted to predict age-dependent changes in target tissue exposure to eight pyrethroids. The purpose of this age-dependent dosimetry was to calculate a Data Derived Extrapolation Factor (DDEF) to address age-related pharmacokinetic differences for pyrethroids in humans. We developed a generic human PBPK model for pyrethroids based on our previously published rat model that was developed with in vivo rat data. The results demonstrated that the age-related differences in internal exposure to pyrethroids in the brain are largely determined by the differences in metabolic capacity and in physiology for pyrethroids between children and adults. The most important conclusion from our research is that, given an identical external exposure, the internal (target tissue) concentration is equal or lower in children than in adults in response to the same level of exposure to a pyrethroid. Our results show that, based on the use of the Life Stage PBPK models with eight pyrethroids, DDEF values are essentially close to 1, resulting in a DDEF for age-related pharmacokinetic differences of 1. For risk assessment purposes, this indicates that no additional adjustment factor is necessary to account for age-related pharmacokinetic differences for these pyrethroids.
... Kissel et al. (1998), cited on page 47 is a secondary reference and the primary reference should be cited. Primary information on the distinction between hand to mouth touching and insertion can be found by comparing Zartarian et al. (1997) with Zartarian et al. (1998). ...
... The rates for older children (25-60 months) was half that of the younger children. Because of the difference in data collection methodology compared with that used by the group at Stanford (Zartarian et al. 1997 and1998) and by the group at EOHSI (Reed et al. 1999), further work is needed to understand the differences in reported activities. It may be that the work of Zartarian and Reed, which is the basis of current EPA hand-to-mouth rates used in the exposure models, is an underestimate. ...
... The video footage can later be re-visited to extract information of interest. In the past, Stanford's Exposure Research Group (ERG) developed and used a videotaping and video-translation methodology to quantify children's activity patterns relevant for dermal, inhalation, and some forms of non-dietary ingestion exposure to chemical residues (Zartarian et al. 1997a(Zartarian et al. ,b, 1998Auyeung et al. 2004Auyeung et al. , 2006Ferguson et al. 2006;Xue et al. 2007). That previous methodology has been tailored to extract children's activity patterns from meal events relevant to quantifying enhanced ingestion exposure of contaminant residues (i.e., nondietary ingestion exposure) and is presented in this article. ...
... The first project involved four farm-worker children videotaped from a previous pilot study conducted by the Stanford Exposure Group (Zartarian et al. 1995). Other activity patterns for dermal activities have been published on this small group of children (Zartarian et al. 1997a(Zartarian et al. , 1998. These children were Mexican or of Mexican-American descent, two boys and two girls, between the ages of 2 and 4 years. ...
During meal events, a child's food can be contaminated through contacts with objects and surfaces, and/or unwashed hands that have chemical residues, increasing ingestion exposure of contaminants for the child. This is not surprising, given that very young children eat more with the hands than adults, are active, and play with toys and objects while eating. In addition, children's unwashed hands and toys are commonly inserted into their mouths during meal events increasing exposure. By observing children during their meal events, information can be gathered on the frequency and duration of contacts between objects, foods, and hands, and the sequence of events before the hands, foods, or objects are inserted into the mouth. This paper describes the process of refining a videotaping and video-translation methodology to capture micro-level activity time series (MLATS), in order to better quantify total exposure for young children as a result of their behavior during meal events and cross-contamination of foods and hands. These MLATS can be seen as detailed activity patterns that provide useful data, along with transfer coefficients and environmental concentration to estimate exposures.
... Contact probabilities were derived from CHAD and several peer-reviewed studies (Zartarian et al., 1997;Auyeung et al., 2006), determined separately for the kitchen/bathroom (presumed to be highly treated areas) and for the remainder of the living space. For the fraction of time spent in rooms in the home, we reviewed activity diaries from CHAD for children ages 1-5 years that lived in an apartment and had a household income below $40,000 (approximately twice the national poverty level for a family of 4) (Federal Register, 2008). ...
... Possible surfaces contacted can be smooth, textured, or no surface. Data from Zartarian et al. (1997) were used for the no surface contact probability, and we allocated the remaining probability to smooth and textured surface contacts based upon their proportional contacts per hour from Auyeung et al. (2006). We determined best-fit distributions for the room contact probabilities and created triangle distributions for the surface contact probabilities, using average proportional difference for the mode and determining the minimum and maximum values from approximate variability seen in the contacts per hour by surface. ...
Pesticide exposure in urban low-income residential environments may be elevated as a result of persistent application due to severe pest infestation. Children living in this environment may be a sensitive subpopulation for these non-dietary exposures, due to their physiological and behavioral differences. In this study, we provide an exposure modeling framework to simulate exposures for children in this environment and assess dominant exposure routes and sources of exposure variability, in order to characterize factors that influence risk. We use a dataset of pesticide measurements collected in 42 low-income dwellings, including vacuum dust and floor wipe samples from kitchens and living rooms. We fit distributions to the concentration measurements for the organophosphates measured, chlorpyrifos and diazinon, and the most prevalent pyrethroids (permethrin, cypermethrin, and cyfluthrin), and simulated 1000 homes from the distributions. Concentration measurements were then connected with activity pattern data, short-term dermal and ingestion exposures and absorbed doses were simulated for children ages 1-5 years. For both pesticide groups, exposure values ranged widely, with concentration values contributing most significantly to exposure variability, although approximately 20-fold variability was attributable to exposure factors alone. In addition, upper percentile exposed children usually had both higher concentrations as well as greater influences from exposure and dose factors. Differences were also seen across pesticide groups in dominant exposure pathways. Our analyses indicate a profile of factors that describe individuals likely to receive high doses of one or multiple pesticides and could allow for more targeted intervention strategies. More generally, this work provides a standard framework to evaluate and describe exposures to prevalent residential pesticides via multiple pathways.
... Mouthing and hand contact frequencies are key parameters for estimating non-dietary ingestion and dermal exposure (Zartarian et al., 2006;Nicas and Best, 2008;Stapleton et al., 2008;Julian et al., 2009;Schleier et al., 2009;Macedo et al., 2010;Tulve et al., 2010), as well as soil/dust ingestion rates (Ö zkaynak et al., 2010) critical for most hazardous site clean-up risk assessments including Superfund sites (US EPA, 2004). Several studies have quantified these mouthing and hand contact behaviors in children (Zartarian et al., 1997aBrinkman et al., 1999;Reed et al., 1999;Freeman et al., 2001Freeman et al., , 2005Tulve et al., 2002;AuYeung et al., 2004;Black et al., 2005;Auyeung et al., 2006;Beamer et al., 2008); however, we know of only one other study that has reported any data on children over 6 years of age (Freeman et al., 2001). Meta-analyses of the data collected from younger children have indicated that mouthing decreases with age and other studies have reported differences by age in the frequency, with which children contact different types of objects or fomites with their hands (Freeman et al., 2001;Auyeung et al., 2006;Beamer et al., 2008). ...
... Although this study has a small sample size and is limited to children's behaviors in the outdoor environment, this represents the first study that we are aware of, which specifically reports the quantified micro-activity of the older children (7-12-years old), necessary for estimating dermal and incidental ingestion exposures. As has been reported for younger children (Zartarian et al., 1997a Auyeung et al., 2006;Beamer et al., 2008), these children also had frequent contacts (415 contacts/h and 4600 contacts/h with the mouth and both the hands, respectively) of short duration (o2 s and o3 s for the mouth and both the hands, respectively), regardless of socioeconomic status or race/ethnicity . The data are right skewed and median values are probably a better representation of the central tendency of the data than mean values, as they are less influenced by the few high values. ...
Estimation of aggregate exposure and risk requires detailed information regarding dermal contact and mouthing activity. We analyzed micro-level activity time series (MLATS) of children aged 7-12 years to quantify these contact behaviors and evaluate differences by age and gender. In all, 18 children, aged 7-12 years, were videotaped while playing outdoors. Video footage was transcribed via Virtual Timing Device (VTD) software. We calculated the hand and mouth contact frequency, hourly duration and median duration of contact with 16 object categories. Median mouthing frequencies were 12.6 events/h and 2.6 events/h for hands and non-dietary objects, respectively. Median hourly mouthing duration was 0.4 min/h and 0.1 min/h with hands and objects. Median mouthing contact duration was 1 s and 1.5 s with hands and objects, respectively. The median object contact frequency for both the hands combined was 537.3 events/h with an hourly contact duration of 81.8 min/h and a median contact duration of 3 s. There were no significant differences in the mouthing activity between genders or age groups. Female children had longer and more frequent hand contacts with several surface types. Age was negatively correlated with hand contacts of floor and wood surfaces. Contact frequencies in this study are higher than current regulatory recommendations for this age group.
... There are also a number of other intriguing technologies in development worth mentioning. These include time-event recorders, wearable computers, and VideoTraq translation software for videotaped activities (Starner et al., 1997;Zartarian et al, 1997;Zartarian et al, 1997). As yet, none of these technologies has been used to track media use, nor have they been used very much in general. ...
... There are also a number of other intriguing technologies in development worth mentioning. These include time-event recorders, wearable computers, and VideoTraq translation software for videotaped activities (Starner et al., 1997;Zartarian et al, 1997;Zartarian et al, 1997). As yet, none of these technologies has been used to track media use, nor have they been used very much in general. ...
In this new and rapidly changing era of digital technology, there is increasing consensus among media scholars that there is an urgent need to develop measurement approaches which more adequately capture media use The overarching goal of this paper is facilitate the development of measurement approaches appropriate for capturing children's media use in the digital age. The paper outlines various approaches to measurement, focusing mainly on those which have figured prominently in major existing studies of children's media use. We identify issues related to each technique, including advantages and disadvantages. We also include a review of existing empirical comparisons of various methodologies. The paper is intended to foster discussion of the best ways to further research and knowledge regarding the impact of media on children.
... These rates vary by developmental stage and among individuals within a given stage (Bearer, 1995 ). Behaviors of children (e.g., mouthing surfaces and crawling ) further promote exposure (Zartarian et al., 1995(Zartarian et al., , 1997Reed et al., 1999 ). Collectively, these differences leave children more susceptible to exposures (Goldman, 1995 ). ...
... Pound for pound of body weight, children eat more, breath more, and have a faster metabolism. Behaviorally, they play on the floor or lawn where pesticides are commonly applied and have more frequent hand-to -mouth contacts ( Zartarian et al., 1995( Zartarian et al., , 1997Bradman et al., 1997;Eskenazi et al., 1999;Reed et al., 1999) . Based on the laboratory reference range procedure, 5% exposure was expected. ...
Pesticide exposure may differentially impact young children; they live closer to the ground and take in greater amounts of food relative to body mass than older children or adults. We are using an organophosphate (OP) urinary biomarker screen (gas chromatography with flame photometric detection, GC/FPD) to evaluate pesticide exposure among 154 children < or = 6 years of age living in a heavily farmed border (US-Mexico) community. The screen detects diethylphosphates (DEPs) and dimethylphosphates (DMPs) above a reference range of 1000 non-occupationally exposed individuals (DL=25 microg/g creatinine, Cr). At least one metabolite was detected for 33% of the subjects; many samples contained multiple biomarkers. DEP was detected in 5% of the subjects. DMP and DMTP were frequently measured (25% and 26%, respectively). Biomarker concentrations are adjusted by the body's metabolism of Cr as an indicator of urine dilution. Cr concentrations were examined separately to evaluate their effect on internal dose measures. Cr concentrations were significantly different by season (K-W=0.83, P=0.022). Significant differences exist between the autumn:spring (P=0.038) Cr concentrations and between summer:autumn (P=0.041) Cr concentrations based on Mann-Whitney U=1070.5, z=-2.041, (P=0.041). Our analysis of NHANES III data did not reflect seasonal Cr differences for 6 year olds. No younger children were included. Absorbed daily dose (ADD) estimates were calculated for children with the highest concentrations of metabolite. Calculations are theoretical values assuming that the entirety of a given metabolite was metabolized from a single pesticide. Several class appropriate pesticides were evaluated. For the children with the highest levels, almost all estimated ADDs exceeded the RfD. Although the actual metabolite concentrations dropped appreciably, ADD were still exceeded RfDs at the 95th percentile. The urinary OP screen was effective in identifying subjects with atypical internal doses. Daily Cr yield is a critical component in ADD calculations. Cr variability produces differences in internal dose measurement and estimates of ADD independent of exposure. Cr variability among young children needs to be examined, and caution should be applied when evaluating Cr adjusted internal doses for children.
... Meso and macro activities can often be derived from micro-activity patterns. Videotaping and video-translation techniques can be used to collect very detailed micro activity patterns (i.e., lines of contact patterns, locations visited) useful for the dermal route that relies on understanding the variability in contact patterns (Zartarian et al., 1997). Using videotaping and videotranslation methodologies, allows for sequences of activity patterns, from which can be derived frequency and duration of contact with object and surfaces and time spent in various micro-environments. ...
... The potential for food and foodrelated objects to contain contaminants of interest was taken into account in several studies. Five studies recorded contacts with food and contacts between the child's mouth and the child's own hand or body, but not between the child's mouth and other individual's hands and bodies [22,23,[28][29][30]. Authors of two studies included feeding events and contacts between the child's mouth and any individual's hands [31,32]. ...
Children are exposed to environmental contaminants through direct ingestion of water, food, soil, and feces, and through indirect ingestion due to mouthing hands and objects. We quantified ingestion among 30 rural Bangladeshi children <4 years old, recording every item touched or mouthed during 6-h video observations that occurred annually for 3 years. We calculated the frequency and duration of mouthing and the prevalence of mouth contacts with soil and feces. We compared the mouthing frequency distributions to those from US children to evaluate the appropriateness of applying the US data to the Bangladeshi context. Median hand mouthing frequency was 97–160 times/h and object mouthing 23–50 times/h among the five age groups assessed. For more than half of the children, >75% of all hand mouthing was associated with eating. The frequency of hand mouthing not related to eating was similar to the frequency of all hand-mouthing among children in the US. Object-mouthing frequency was higher among Bangladeshi children compared to US children. There was low intra-child correlation of mouthing frequencies over our longitudinal visits. Our results suggest that children’s hand- and object-mouthing vary by geography and culture and that future exposure assessments can be cross-sectional if the goal is to estimate population-level distributions of mouthing frequencies. Of all observations, a child consumed soil in 23% and feces in 1%.
... Children are exposed to soil during their play activities and exhibit unique activity patterns, such as frequent hand and mouth contact behaviors with objects/surfaces (AuYeung et al., 2004(AuYeung et al., , 2006Beamer et al., 2008Beamer et al., , 2012Black et al., 2005;Reed et al., 1999;Tsou et al., 2015;Tulve et al., 2002;Zartarian et al., 1995Zartarian et al., , 1997aZartarian et al., , 1997bZartarian et al., , 1998. Metals from various natural and anthropogenic sources can accumulate in soil (Khan et al., 2008;Zhang et al., 2010). ...
... The key system-specific parameter is the contact frequency FQ os,I for the microactivity approach. The frequency of contacts for carpet, vinyl floor and objects can be obtained from various studies on children's microactivities (AuYeung et al., 2006;Freeman et al., 2000;Freeman et al., 2005;Reed et al., 1999;Zartarian et al., 1996), and Shin et al. (Shin et al., 2012) gave the average values of 11, 12 and 115 events/day. 3.3.2.3. ...
... In structured observation, trained observers use a structured observation instrument to guide them in recording a child's hand and/or mouth contacts in real time. In video observation, videographers record a child's activities on video and trained analysts subsequently watch the video to record the child's contacts, often employing a computer-aided video translation software such as the Virtual Timing Device™ [38]. To gather detailed micro-level activity time-series data regarding hand-and mouth-contacts, a video is usually translated two or three times [28][29][30], thus requiring three to four times longer to collect data than with structured observation. ...
Children are exposed to environmental contaminants by placing contaminated hands or objects in their mouths. We quantified hand- and object-mouthing frequencies of Bangladeshi children and determined if they differ from those of U.S. children to evaluate the appropriateness of applying U.S. exposure models in other socio-cultural contexts. We conducted a five-hour structured observation of the mouthing behaviors of 148 rural Bangladeshi children aged 3-18 months. We modeled mouthing frequencies using 2-parameter Weibull distributions to compare the modeled medians with those of U.S. children. In Bangladesh the median frequency of hand-mouthing was 37.3 contacts/h for children 3-6 months old, 34.4 contacts/h for children 6-12 months old, and 29.7 contacts/h for children 12-18 months old. The median frequency of object-mouthing was 23.1 contacts/h for children 3-6 months old, 29.6 contacts/h for children 6-12 months old, and 15.2 contacts/h for children 12-18 months old. At all ages both hand- and object-mouthing frequencies were higher than those of U.S. children. Mouthing frequencies were not associated with child location (indoor/outdoor). Using hand- and object-mouthing exposure models from U.S. and other high-income countries might not accurately estimate children's exposure to environmental contaminants via mouthing in low- and middle-income countries.
... 6 Young children touch dirt, smooth surfaces, and objects to their mouths multiple times per hour. 8,9 These behaviors may all contribute to an increased risk of physical exposure to agents, toxins, and other hazards during CBRN incidents. In addition, depending on age and development, children may not have the communication skills, motor skills, or judgment to effectively move toward safety in a dangerous situation. ...
Children represent nearly a quarter of the US population, but their unique needs in chemical, biological, radiological, and nuclear (CBRN) emergencies may not be well understood by public health and emergency management personnel or even clinicians. Children are different from adults physically, developmentally, and socially. These characteristics have implications for providing care in CBRN disasters, making resulting illness in children challenging to prevent, identify, and treat. This article discusses these distinct physical, developmental, and social traits and characteristics of children in the context of the science behind exposure to, health effects from, and treatment for the threat agents potentially present in CBRN incidents.
... Once pyrethroid pesticides have entered the home, the carpets and cushioned furniture can act as repositories for pesticides (Colt et al., 2004;Starr et al., 2008). High levels of pesticides in carpet dust is a particular concern for young children who, due to their continual exploration of their environments, spend a large amount of time on the floor and have increased hand to mouth activity, resulting in increased exposure to the pollutants through dermal and non-dietary ingestion routes (Fenske et al., 1990;Gurunathan et al., 1998;Zartarian et al., 1997). ...
... Families living in close proximity to farms may have higher than average pyrethroid exposure due to household pesticide use, drift from agricultural application and take-home exposure pathways from occupational use by another family member (Curl et al., 2002;Harnly et al., 2005;Lu et al., 2000;You et al., 2004). High levels of pesticides in carpet dust are a particular concern for young children who, due to their continual exploration of their environments, spend a large amount of time on the floor and have increased hand to mouth activity, resulting in increased exposure to pollutants through dermal and non-dietary ingestion routes (Fenske et al., 1990;Gurunathan et al., 1998;Moya et al., 2004;Zartarian et al., 1997). These two factors combined make children living in agricultural communities especially susceptible to pesticide exposure (Arcury et al., 2007;Bradman et al., 2007). ...
... It is easy to imagine a scenario where children would be coming into contact with treated wood many times during the day. Since kids have a tendency to put their hands in their mouths frequently (an average of 6 and up to 45 times per hour, according to a recent study), it is likely that kids would be ingesting arsenic from each of these sources (Zartarian 1997). ...
... Young children may be exposed to pesticides due to certain oral behaviors while exploring their environment or through dermal contact with floors and other surfaces (Zartarian et al. 1997;Gurunathan et al. 1998;Fenske et al. 1990). Children who live near agricultural communities may be exposed more frequently due to pesticides that are tracked into their homes or as a result of pesticide drift (Moses et al. 1993;Wiles et al. 1994;Shalat et al. 2001;Eskenazi et al. 1999;Zahm et al. 1998). ...
Relatively little information is available regarding pesticide exposures among children living in agricultural settings. This study assessed the relationship between household distance from an agricultural field and pesticide levels in house dust and on children's hands. A methodology for estimating childhood exposure by sampling house dust and children's hand-rinse samples was also evaluated. Four rounds of sampling were conducted, with samples collected in each round from approximately 30 houses and 45 children between the ages of 5 months and 36 months. Samples were prepared for chemical analysis and analyzed for organochlorine (OC) and/or organophosphate (OP) pesticides using gas chromatography coupled with either an electron capture or a nitrogen/phosphorus detector. OCs were detected at much lower concentrations than OPs. Additionally, no relationship existed between household proximity to the field and the concentration of pesticides in the house dust or hand-rinse samples (all corresponding p-values were greater than .05). The data suggest that pesticides in house dust and on children's hands originate from a variety of sources, which may include indoor use of pesticides; pesticides used on lawns, gardens and domestic animals; and pesticide drift from agricultural fields.
... Observations have been used to obtain detailed data about activity patterns for which self -reports or parental reports are inadequate ( Zartarian et al., 1995( Zartarian et al., , 1997Reed et al., 1999 ). Zartarian observed four farm children in California and Reed observed 30 children in homes and day -care programs in New Jersey. ...
Children have been one of the least-studied populations for estimating environmental exposure, even though they are cited as a sensitive subgroup for diseases derived from environmental exposure. This trend appears to be changing as more studies are conducted with children as subjects. It consequently becomes increasingly important to gather and use observational data in all phases of the study. Observational data are the key for both defining the pathway of exposure and for assessing effectiveness of the data-collection protocols. Obtaining quality data from a study involving children requires: efficient use of observational data, collection of meaningful personal and microenvironmental samples, linkage of observational data to the collected samples, and personnel trained to work with children using pilot-tested protocols. Although all of these help to ensure the quality of the data, the utility of the data is often determined by observational feedback from those who collected it. Laboratory-derived protocols should be living documents and observations from the field should be used to modify the data-collection methods when practical.
... A new field of activity data gathering started in the mid -1990s oriented toward obtaining information on hand -tomouth and related activities, usually for children ( Zartarian et al., 1995( Zartarian et al., , 1997a( Zartarian et al., ,b, 1998Reed et al., 1999 ). These data are very important for understanding non -dietary ingestion and dermal absorption, but little information exists to quantify this type of activity . ...
EPA's National Exposure Research Laboratory (NERL) has combined data from 12 U.S. studies related to human activities into one comprehensive data system that can be accessed via the Internet. The data system is called the Consolidated Human Activity Database (CHAD) and is available at http:// www.epa.gov/nerl/. CHAD contains 22,968 person days of activity and is designed to assist exposure assessors and modelers in constructing population "cohorts" of people with specified characteristics that are suitable for subsequent analysis or modeling. This paper describes the studies comprising CHAD and the various intellectual foundations that underlay the gathering of human activity pattern data. Next, it provides a brief overview of the Internet version of CHAD, and discusses how the program was formulated. Emphasis is placed on how activity-specific energy expenditure estimates were developed. Finally, the paper recommends steps that should be taken to improve the collection of activity data that would improve energy expenditure estimates and related information needed for physiologically based exposure dose modeling efforts.
... A potentially greater problem involves modification of the child's activities due to the invasive presence of the video camera. The primary caretaker may also directly or indirectly modify the child's behavior by confining the child indoors, treating the videotapers as guests or otherwise altering the household routine (Zartarian et al., 1997a,b ) . Both diary surveys and videography are time -intensive, invasive, and expensive. ...
Contaminated site cleanup decisions may require estimation of dermal exposures to soil. Telephone surveys represent one means of obtaining relevant activity pattern data. The initial Soil Contact Survey (SCS-I), which primarily gathered information on the activities of adults, was conducted in 1996. Data describing adult behaviors have been previously reported. Results from a second Soil Contact Survey (SCS-II), performed in 1998-1999 and focused on children's activity patterns, are reported here. Telephone surveys were used to query a randomly selected sample of U.S. households. A randomly chosen child, under the age of 18 years, was targeted in each responding household having children. Play activities as well as bathing patterns were investigated to quantify total exposure time, defined as activity time plus delay until washing. Of 680 total survey respondents, 500 (73.5%) reported that their child played outdoors on bare dirt or mixed grass and dirt surfaces. Among these "players," the median reported play frequency was 7 days/week in warm weather and 3 days/week in cold weather. Median play duration was 3 h/day in warm weather and 1 h/day in cold weather. Hand washes were reported to occur a median of 4 times per day in both warm and cold weather months. Bath or shower median frequency was seven times per week in both warm and cold weather. Finally, based on clothing choice data gathered in SCS-I, a median of about 37% of total skin surface is estimated to be exposed during young children's warm weather outdoor play.
Skin adherence (SA) of soil affects exposure from soil contaminants through dermal routes via loading on the skin and through ingestion routes through hand to mouth activities. The objectives of this study were to evaluate the relationships between adherence versus child-specific and environmental factors. Two sets of soil-to-skin adherence were evaluated. The first was based on loading on hands following hand presses (Hand SA). The second was based on body rinses following one hour of play activities on the beach (Body SA). Results for 98–119 children conducted at four beach sites show that mean Hand SA was 35.7 mg/cm2 (std. dev. 41.8 mg/cm2), while Body SA based on full coverage was 352.3 mg/cm2 (std. dev. 250.4 mg/cm2). Statistically significant differences in Body SA were observed between male (419.2 mg/cm2) and female (300.4 mg/cm2) children (p < 0.05). No significant difference by sex was found for Hand SA. Other statistically different observations were that Hand SA (p < 0.05), but not Body SA, differed across the four beaches (p < 0.05). For Hand SA, this difference was associated soil size variability across the beaches. Hand and Body SA values measured during this study are recommended for use in risk assessments that evaluate beach exposures to oil spill chemicals for young children.
Container-based sanitation (CBS) within a comprehensive service system value chain offers a low-cost sanitation option with potential for revenue generation, but may increase microbial health risks to sanitation service workers. This study assessed occupational exposure to rotavirus and Shigella spp. during CBS urine collection and subsequent struvite fertilizer production in eThekwini, South Africa. Primary data included high resolution sequences of hand-object contacts from annotated video, and measurement of fecal contamination from urine and surfaces likely to be contacted. A stochastic model incorporated chronological surface contacts, pathogen concentrations in urine, and literature data on transfer efficiencies of pathogens to model pathogen concentrations on hands and risk of infection from hand-to-mouth contacts. The probability of infection was highest from exposure to rotavirus during urine collection (~10-1) and struvite production (~10-2), though risks from Shigella spp. during urine collection (~10-3) and struvite production (~10-4) were non-negligible. Notably, risk of infection was higher during urine collection than during struvite production due to contact with contaminated urine transport containers. In the scale-up of CBS, disinfection of urine transport containers is expected to reduce pathogen transmission. Exposure data from this study can be used to evaluate the effectiveness of measures to protect sanitation service workers.
Background: Children must be recognized as a sensitive population based on having biological systems and organs in various stages of development. The processes of absorption, distribution, metabolism and elimination of environmental contaminants within a child’s body are considered less advanced than those of adults, making them more susceptible to disease outcomes following even small doses. Children’s unique activities of crawling and practicing increased hand-to-mouth ingestion also make them vulnerable to greater exposures by certain contaminants within specific environments. Approach: There is a need to review the field of children’s environmental exposures in order to understand trends and identify gaps in research, which may lead to better protection of this vulnerable and sensitive population. Therefore, explored here are previously published contemporary works in the broad area of children’s environmental exposures and potential impact on health from around the world. A discussion of children’s exposure to environmental contaminants is best organized under the last four steps of a risk assessment approach: hazard identification, dose-response assessment, exposure assessment (including children’s activity patterns) and risk characterization. We first consider the many exposure hazards that exist in the indoor and outdoor environments, and emerging contaminants of concern that may help guide the risk assessment process in identifying focus areas for children. A section on special diseases of concern is also included. Conclusions: The field of children’s exposures to environmental contaminants is broad. Although there are some well-studied areas offering much insight into children exposures, research is still needed to further our understanding of exposures to newer compounds, growing disease trends and the role of gene-environment interactions that modify adverse health outcomes. It is clear that behaviors of adults and children play a role in reducing or increasing a child’s exposure, where strategies to better communicate and implement risk modifying behaviors are needed, and can be more effective than implementing changes in the physical environment.
Non-dietary ingestion is an important exposure pathway for children owing to their frequent hand-to-mouth and object-to-mouth activities involving soil and dust contacts. We used videotaping and the computer-based translating methods to quantify the mouthing activity information for 24 children ages 3 to <6 years old living in Taiwan. We also reviewed the entire mouthing activity data collected during the project to determine the lesser studied information on hand surface areas mouthed by children ages <6 years old. The median indoor hand-to-mouth and object-to-mouth frequencies were found to be 10 and 4.3 contacts/h, respectively. Hand-to-mouth and object-to-mouth contact frequencies used in exposure assessments for children ages 3 to <6 years old in this study were similar to the recommended values reported in United States. Exposure Factors Handbook for comparable age US children. The average fractions of the hand area mouthed for children 6 to <12 months, 1 to <2 years, 2 to <3 years, and 3 to <6 years old were 0.12, 0.12, 0.13, and 0.09, respectively. The fraction of hand area mouthed by children was found to be significantly and negatively correlated with their age. About half of the total hand-to-mouth contact events involved immersion of part of a hand or a finger into the mouth. The findings from this study extend the available mouthing activity information for 3 to <6 years old children and also provide new data for an Asian country, allowing comparison of results with western values collected mostly in the United States.Journal of Exposure Science and Environmental Epidemiology advance online publication, 25 January 2017; doi:10.1038/jes.2016.87.
Objectives: Time location data are critical for accurately estimating personal exposures. This review papers summarized various measurement methods of time location pattern for air pollution exposure assessment. Methods: Forty manuscripts (papers, books and reports) were reviewed to comprehensively describe time location measurement methods. Results: This review included traditional methods such as time activity diary, questionnaire, observation, focus group and newly developed technical methods including global positioning system, web, radio frequency identification and ultrasound detection. Some research applied a combination of methods. Conclusion: Although various methods have been used to collect time location data, further development of accurate measurement methods for time location data is needed.
Recent awareness of the generally higher levels of indoor residential exposures relative to outdoor for many chemicals has led to an increasing focus on indoor sources of exposures to chemicals in the residential environment. The TEAM studies have shifted the emphasis to indoor sources of exposures, rather than outdoor ambient sources as the primary contributor to indoor inhalation exposures, as discussed in Chapter 4. This is partly due to (1) the locally important sources of exposure (source terms) provided by some consumer products relative to outdoor levels, (2) time-activity data, which indicate that people spend about 90 percent of their time in indoor environments, and (3) the move over the last couple of decades to energy-efficient residences, which mean less outside air infiltration and more recirculation of indoor releases. Indoor agents or chemicals potentially include a great variety of compounds in consumer products available to the general public (Driver and Whitmyre 1996, Whitmyre et al. 1997). Indeed, for certain specific chemicals, consumer products are the main source of emissions and exposure in the indoor residential environment. Assessment of potential consumer exposures has been recognized as a key component of the overall risk evaluation process for consumer products.
Young children's mouthing activities thought to be among the most important exposure pathways. Unfortunately, mouthing activity studies have only been conducted in a few countries. In the current study, we used videotaping and computer-based translating method to obtain mouthing activity data for 66 children aged 7-35 months in Taiwan. The median indoor hand-to-mouth and object-to-mouth frequencies were 8.91 and 11.39 contacts/h, respectively. The median indoor hand-to-mouth and object-to-mouth hourly contact durations were 0.34 and 0.46 min/h, respectively. The indoor object-to-mouth activities were significantly and negatively correlated with age. Children aged 12 to <24 months in the current study had lower indoor hand-to-mouth and object-to-mouth frequencies than children of same age group in the United States. We also found that indoor mouthing duration with pacifier was significantly and negatively correlated with indoor mouthing duration with other non-dietary objects. The results of the current study indicate that the mouthing behaviors may be different between different countries or populations with different ethnic or lifestyle characteristics. We conclude that using hand-to-mouth frequency values from the current literature may not be most reliable for estimating non-dietary exposures of young children living in Taiwan or even in other similar Asian countries.Journal of Exposure Science and Environmental Epidemiology advance online publication, 16 July 2014; doi:10.1038/jes.2014.50.
Despite the relatively long history of incorporating child-specific safety or exposure factors into U.S. health risk assessments, there has been a growing perception that past scientific and regulatory approaches were not sufficiently protective of infants and children. To address these concerns, a wide range of activities have occurred over the last few years that will likely generate new information on child-specific issues and identify data gaps in current knowledge about children's exposures and health risks. For example, the new publication by the Centers for Disease Control and Prevention, National Report on Human Exposure to Environmental Chemicals, will provide unique information on environmental chemical exposures in the U.S. population using biomonitoring (i.e., blood and urine) analyses. Although preliminary reviews have attempted to summarize what is known about the factors that influence children's exposure and sensitivity to environmental contaminants, there does not appear to be a comprehensive published summary of children's exposure assessment methodologies, or clear guidance on how to prioritize future research needs or deal with data uncertainties. In this paper, we provide an overview of the traditional human health risk assessment paradigm, as well as a reasonably complete discussion of how to assess children's exposures for human health risk assessments via inhalation, dermal, and ingestion routes. Several additional approaches are also discussed that might be worthwhile components of future children's exposure assessments, including: (1) probabilistic (Monte Carlo) techniques, (2) formal expert judgment studies, and (3) value-of-information (VOI) analyses. The information presented here should be useful for persons involved in child-specific exposure and risk evaluations, such as those conducted under the Voluntary Children's Chemical Evaluation Program (VCCEP) or associated with registration of pesticides or other chemicals. Over 150 of the most pertinent references for conducting assessments of children potentially exposed to chemicals in their environment are cited.
A computer-controlled mechanical chamber was used to perform multiple contacts between human cadaver skin or cotton sheet samples and soil-laden carpet or aluminum foil to measure mass soil transfer. The amount transferred was measured with an analytical balance. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 s) were varied for 760 separate multiple contact experiments, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 and ≥ 139.7 < 381 μm) were used. Through parametric and non-parametric tests, this article specifically looks at the influence and interaction of these experimental parameters on the transfer of soil or sand to human skin during multiple contacts. The relationships between the amount of soil or sand that transfers for a first contact, for a second contact, and overall are also presented. On average, a second contact added an additional 8% of soil or sand to the adherence material (i.e., cloth, skin). The experimental variables of pressure, time, soil size, and soil type had less influence on the magnitude of transfer for the second contact as compared to the first contact.
Infants' dermal exposures to environmental contaminants are expected to be different and, in many cases, much higher than adults. Because of the potential importance of the dermal exposure route, there is currently a significant amount of work being conducted to reduce the uncertainties associated with assessing infants' dermal exposures. A conceptual model of dermal exposure is presented and issues associated with characterizing and assessing these exposures presented. Physiological and behavioral characteristics of infants that impact dermal exposure as well as exposure measurement and assessment approaches are discussed.
Postapplication exposure assessment related to indoor residential application of pesticide products requires consideration of product use information, application methods, chemical-specific deposition, time-dependent availability and transferability of surface residues, reentry time, and temporal location and macro- and microactivity/behavior patterns (Baker et al., 20008.
Baker , S. ,
Driver , J. H. and
McCallum , D. 2000. Residential exposure assessment: A sourcebook, New York, NY: Kluwer Academic/Plenum. View all references). Children's mouthing behavior results in potential postapplication exposure to available pesticides in treated microenvironments through the nondietary ingestion route, in addition to the dermal or inhalation routes. Children's activities and associated behaviors may result in multiple or repeat contact of dermal areas (clothed and unclothed body areas and hands) with treated surfaces, or surfaces that may have indirect sources of residues. Further, some surfaces contacted may have transferable pesticide residues and others may not. Transfer of residues from the indoor residential environment to the dermal surface (e.g., hands) of an individual has been assumed to be linear as a function of time and number of contacts. However, studies suggest that this transfer process to the hands and other body areas may be rapidly saturable. In the most recent U.S. Environmental Protection Agency (EPA), Office of Pesticide Programs (OPP) “Residential Exposure Assessment Standard Operating Procedures” (U.S. EPA, 2012), the input variable for the number of dermal contacts (with treated surfaces) is an exponent, making the relationship nonlinear. Further, removal processes such as hand washing and transfer to untreated surfaces are important to consider. Predictive algorithms for estimating children's hand-to-mouth-related incidental ingestion exposures post pesticide application have been developed by the EPA/OPP and incorporated into probabilistic models. A review of literature addressing variables used to estimate potential incidental ingestion exposure is presented. Data relevant to input variables for predictive algorithms are discussed, including the results of a multiyear, pesticide transferable residue measurement program conducted by the Non-Dietary Exposure Task Force (NDETF) and the associated distributional characterization for this key variable. Sources of conservative bias in current hand-to-mouth, incidental ingestion exposure estimation and the role of biomonitoring to evaluate predicted exposures are discussed.
Reliable exposure-based chemical characterization tools are needed to evaluate and prioritize in a rapid and efficient manner the more than tens of thousands of chemicals in current use. This study applies intake fraction (iF), the integrated incremental intake of a chemical per unit of emission, for a suite of indoor released compounds. A fugacity-based indoor mass-balance model was used to simulate the fate and transport of chemicals for three release scenarios: direct emissions to room air and surface applications to carpet and vinyl. Exposure through inhalation, dermal uptake, and nondietary ingestion was estimated. To compute iF, cumulative intake was summed from all exposure pathways for 20 years based on a scenario with two adults and a 1-year-old child who ages through the simulation. Overall iFs vary by application modes: air release (3.1 × 10(-3) to 6.3 × 10(-3)), carpet application (3.8 × 10(-5) to 6.2 × 10(-3)), and vinyl application (9.0 × 10(-5) to 1.8 × 10(-2)). These iF values serve as initial estimates that offer important insights on variations among chemicals and the potential relative contribution of each pathway over a suite of compounds. The approach from this study is intended for exposure-based prioritization of chemicals released inside homes.
Evaluating the extent of dermal exposure to toxic chemicals requires that researchers determine the adherence of contaminated soil to human skin following surface and object contact. In this research we have used a specifically designed mechanical chamber to control and record pressure, time and area of contact between two surfaces to determine values of soil mass adherence. W e designed a series of n = 387 soil adherence experiments at contact pressure of 20 to 50 kPa, contact times of 10 to 50 seconds, and particle size of <139.7 µm and $139.7 < 381 µm for sand and enriched lawn soil. Soil/sand adherence was determined from aluminum sheets to 8.97 cm human cadaver skin and cotton sheets. 2 Environmental conditions of temperature and humidity were not controlled but recorded. Log transformation of the sand/soil transfer was performed to normalize the distribution. Estimated adjusted means for experimental conditions were exponentiated in order to express them in the original units. Higher pressure (p=0.0002), longer time (p=0.0183), sand (p<0.0001), smaller particle size (p=0.0349) and skin (p<0.0001) were all associated with larger amounts of soil transfer. Amount of soil before transfer (p=0.2171) and temperature (p=0.8391) of the room were not significant in the adjustment, however, humidity (p=0.0073) of the room was associated with higher amounts of soil transfer. This research provides vital information to help understand the magnitude and extent of dermal exposure in and around the home.
In the assessment of exposure to environmental pollutants oral and dermal uptake must be considered in addition to uptake by inhalation. The oral uptake is not only determined by ingestion of food and drinking water but may also depend −especially in the case of young children-on the ingestion of house dust encountered in the indoor environment. In addition, pollutants contained in house dust may also be taken up by dermal contact. A number of house dust sampling procedures are available and used in practice. On the one hand, dust as deposited on a surface over a specific period of time is investigated, on the other hand house dust samples are collected by vacuuming, sweeping or wiping procedures. Similarly, the sample is used in different ways for subsequent analysis: either total dust or a sieved fraction of the dust is analysed. Finally, the result of the determination of house dust components can be given as a mass-related or an arearelated number. The large variety of procedures used in practice is presented and summarised. It is shown that due to the use of different procedures the assessment of exposure to house dust and its components is subject to a number of uncertainties. These uncertainties are caused by the current lack of consensus about the most suitable way for sampling and analysis of house dust. In addition, they originate from variations in individual behaviour in indoor spaces, as demonstrated by information available for children. In the last part of the paper information is given on the success of measures to reduce exposure to house dust. The difficulties related to the evaluation of the results of house dust investigations are discussed.
Daily soil/dust ingestion rates typically used in exposure and risk assessments are based on tracer element studies, which have a number of limitations and do not separate contributions from soil and dust. This article presents an alternate approach of modeling soil and dust ingestion via hand and object mouthing of children, using EPA's SHEDS model. Results for children 3 to <6 years old show that mean and 95th percentile total ingestion of soil and dust values are 68 and 224 mg/day, respectively; mean from soil ingestion, hand-to-mouth dust ingestion, and object-to-mouth dust ingestion are 41 mg/day, 20 mg/day, and 7 mg/day, respectively. In general, hand-to-mouth soil ingestion was the most important pathway, followed by hand-to-mouth dust ingestion, then object-to-mouth dust ingestion. The variability results are most sensitive to inputs on surface loadings, soil-skin adherence, hand mouthing frequency, and hand washing frequency. The predicted total soil and dust ingestion fits a lognormal distribution with geometric mean = 35.7 and geometric standard deviation = 3.3. There are two uncertainty distributions, one below the 20th percentile and the other above. Modeled uncertainties ranged within a factor of 3-30. Mean modeled estimates for soil and dust ingestion are consistent with past information but lower than the central values recommended in the 2008 EPA Child-Specific Exposure Factors Handbook. This new modeling approach, which predicts soil and dust ingestion by pathway, source type, population group, geographic location, and other factors, offers a better characterization of exposures relevant to health risk assessments as compared to using a single value.
Farmworkers' children may have increased pesticide exposure through dermal absorption and non-dietary ingestion, routes that are difficult to measure and model. The Cumulative Aggregate Simulation of Exposure (CASE) model, integrates the complexity of human behavior and variability of exposure processes by combining micro-level activity time series (MLATS) and mechanistic exposure equations. CASE was used to estimate residential non-dietary organophosphate pesticide exposure (i.e., inhalation, dermal, and non-dietary ingestion) to California farmworker children and evaluate the micro-activity approach. MLATS collected from children and distributions developed from pesticide measurements in farmworkers' residences served as inputs. While estimated diazinon exposure was greater for inhalation, chlorpyrifos exposure was greater for the other routes. Greater variability existed between children (sigma(B)(2)=0.22-0.39) than within each child's simulations (sigma(W)(2)=0.01-0.02) for dermal and non-dietary ingestion. Dermal exposure simulations were not significantly different than measured values from dosimeters worn by the children. Non-dietary ingestion exposure estimates were comparable to duplicate diet measurements, indicating this route may contribute substantially to aggregate exposure. The results suggest the importance of the micro-activity approach for estimating non-dietary exposure. Other methods may underestimate exposure via these routes. Model simulations can be used to identify at-risk children and target intervention strategies.
A computer-controlled mechanical chamber was used to control the contact between carpet and aluminum sheet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. The contact parameters of pressure (10-50 kPa) and time (10-50s) were varied for 768 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil particle sizes (<139.7 and 139.7<381 microm) were used. Mean soil mass transfer to cadaver skin was higher than mean transfer to cotton sheets for both carpet and aluminum transfers, and also generally higher pressure was associated with larger amounts of soil transfer for all contact scenarios. The mean soil adherence from carpet was 0.37+/-0.4 mg/cm(2), while the mean soil adherence from aluminum was 0.42+/-0.6 mg/cm(2). For aluminum, smaller soil particle size was associated with more transfer (p=0.0349), while for carpet, larger soil size was associated with more transfer (p<0.0001). Soil type was significant but only for aluminum surface, where sand was associated with higher adherence (p<0.0001). This data set can be used to improve estimates of dermal exposure to contaminants found in soils and dust present in indoor environments.
This investigation quantitatively assessed hand residues of chlorpyrifos and methamidophos in a field setting and sought to explain the residues through application volume and determinants of exposure using application data for 28 subsistence farmers in the Pacific Region of Nicaragua. Hand residues were estimated by recovery of the pesticides by standardized wipe sampling for both hands, analyzed with solvent extraction and gas chromatography with electron capture detector. Application volumes were based on data on individual spraying rates and mixing volumes. Eleven determinants of exposure, related to work practices during mixing and spraying of the pesticides, were assessed for each subject from videotapes. Correlation and regression analyses estimated the associations between hand residues, application volume, pesticide type, and determinants of exposure. Correlations between residues for different hand parts were high (r 0.75-0.98). Total hand residue (sum of residues of parts of both hands) correlated with application volume (r 0.43, p 0.02), not washing hands (r 0.41, p 0.04), spraying nozzle forward (r 0.26, p 0.17), manipulation of hose (r 0.32, p .09), and insecticide type (chlorpyrifos vs. methamidophos; r 0.31, p 0.10). A model that explained total hand residue with these five variables yielded a multiple correlation coefficient of 0.67 (p 0.01). Unmeasured determinants and/or narrow range of the exposure situation probably account for the unexplained variance of the residues.
A computer-controlled mechanical chamber was used to control the contact between carpet samples laden with soil, and human cadaver skin and cotton sheet samples for the measurement of mass soil transfer. Mass soil transfers were converted to adherence factors (mg/cm2) for use in models that estimate dermal exposure to contaminants found in soil media. The contact parameters of pressure (10 to 50 kPa) and time (10 to 50 sec) were varied for 369 experiments of mass soil transfer, where two soil types (play sand and lawn soil) and two soil sizes (< 139.7 microm and > or = 139.7 < 381) were used. Chamber probes were used to record temperature and humidity. Log transformation of the sand/soil transfers was performed to normalize the distribution. Estimated adjusted means for experimental conditions were exponentiated in order to express them in the original units. Mean soil mass transfer to cadaver skin (0.74 mg/cm2) was higher than to cotton sheets (0.21 mg/cm2). Higher pressure (p < 0.0001), and larger particle size (p < 0.0001) were also all associated with larger amounts of soil transfer. The original model was simplified into two by adherence material type (i.e., cadaver skin and cotton sheets) in order to investigate the differential effects of pressure, time, soil size, and soil type on transfer. This research can be used to improve estimates of dermal exposure to contaminants found in home carpets.
Recent studies show that young children can be exposed to pesticides during normal oral exploration of their environment and their level of dermal contact with floors and other surfaces. Children living in agricultural areas may be exposed to higher pesticide levels than other children because of pesticides tracked into their homes by household members, by pesticide drift, by breast milk from their farmworker mother, or by playing in nearby fields. Nevertheless, few studies have assessed the extent of children's pesticide exposure, and no studies have examined whether there are adverse health effects of chronic exposure. There is substantial toxicologic evidence that repeated low-level exposure to organophosphate (OP) pesticides may affect neurodevelopment and growth in developing animals. For example, animal studies have reported neurobehavorial effects such as impairment on maze performance, locomotion, and balance in neonates exposed (italic)in utero(/italic) and during early postnatal life. Possible mechanisms for these effects include inhibition of brain acetylcholinesterase, downregulation of muscarinic receptors, decreased brain DNA synthesis, and reduced brain weight in offspring. Research findings also suggest that it is biologically plausible that OP exposure may be related to respiratory disease in children through dysregulation of the autonomic nervous system. The University of California Berkeley Center for Children's Environmental Health Research is working to build a community-university partnership to study the environmental health of rural children. This Center for the Health Assessment of Mothers and Children of Salinas, or CHAMACOS in Monterey County, California, will assess (italic)in utero(/italic) and postnatal OP pesticide exposure and the relationship of exposure to neurodevelopment, growth, and symptoms of respiratory illness in children. The ultimate goal of the center is to translate research findings into a reduction of children's exposure to pesticides and other environmental agents, and thereby reduce the incidence of environmentally related disease.
To help address the Food Quality Protection Act of 1996, a physically based probabilistic model has been developed to quantify and analyze dermal and nondietary ingestion exposure and dose to pesticides. The Residential Stochastic Human Exposure and Dose Simulation Model for Pesticides (Residential-SHEDS) simulates the exposures and doses of children contacting residues on surfaces in treated residences and on turf in treated residential yards. The simulations combine sequential time-location-activity information from children's diaries with microlevel videotaped activity data, probability distributions of measured surface residues and exposure factors, and pharmacokinetic rate constants. Model outputs include individual profiles and population statistics for daily dermal loading, mass in the blood compartment, ingested residue via nondietary objects, and mass of eliminated metabolite, as well as contributions from various routes, pathways, and media. To illustrate the capabilities of the model framework, we applied Residential-SHEDS to estimate children's residential exposure and dose to chlorpyrifos for 12 exposure scenarios: 2 age groups (0-4 and 5-9 years); 2 indoor pesticide application methods (broadcast and crack and crevice); and 3 postindoor application time periods (< 1, 1-7, and 8-30 days). Independent residential turf applications (liquid or granular) were included in each of these scenarios. Despite the current data limitations and model assumptions, the case study predicts exposure and dose estimates that compare well to measurements in the published literature, and provides insights to the relative importance of exposure scenarios and pathways.
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We review the factors influencing children's exposure to environmental contaminants and the data available to characterize and assess that exposure. Children's activity pattern data requirements are demonstrated in the context of the algorithms used to estimate exposure by inhalation, dermal contact, and ingestion. Currently, data on children's exposures and activities are insufficient to adequately assess multimedia exposures to environmental contaminants. As a result, regulators use a series of default assumptions and exposure factors when conducting exposure assessments. Data to reduce uncertainty in the assumptions and exposure estimates are needed to ensure chemicals are regulated appropriately to protect children's health. To improve the database, advancement in the following general areas of research is required: identification of appropriate age/developmental benchmarks for categorizing children in exposure assessment; development and improvement of methods for monitoring children's exposures and activities; collection of activity pattern data for children (especially young children) required to assess exposure by all routes; collection of data on concentrations of environmental contaminants, biomarkers, and transfer coefficients that can be used as inputs to aggregate exposure models.
Recently, intense attention has been given to children's health issues, particularly in the use of consumer products. Because of this attention, researchers have been planning and initiating studies specifically aimed at developing both toxicology data and exposure data directed to improve our understanding of industrial and consumer product chemical impacts on children's health. To ensure that this research is focused on the highest priority chemicals, we present a methodology for determining and prioritizing the higher hazard chemicals and scenarios for which children could be disproportionately or highly exposed. This tiered approach includes a screening step for initial chemical selection, a hazard assessment based on no- or lowest-observed-adverse-effect levels, and a margin of exposure (MOE) calculation. The initial chemical screen focuses on the chemical presence in specific media that are special to children, such as foods children regularly eat and drink, residential or school air, products children use, and soil and dust in and around residences. Data from the literature or from models serve as the initial exposure estimate. This methodology would allow us to focus on those chemicals to which children are most exposed that are also associated with, potentially, the highest risk. Use of the MOE calculation allows for comparison among chemicals, prioritization of chemicals for evaluation and testing, and identification of significant data gaps.
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