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The development and application of the chemical mixture methodology in analysis of potential health impacts from airborne release in emergencies
Abstract
The Chemical Mixture Methodology (CMM) is used for emergency response and safety planning by the US Department of Energy, its contractors and other private and public sector organizations. The CMM estimates potential health impacts on individuals and their ability to take protective actions as a result of exposure to airborne chemical mixtures. It is based on the concentration of each chemical in the mixture at a designated receptor location, the protective action criteria (PAC) providing chemical-specific exposure limit values and the health code numbers (HCNs) that identify the target organ groupings that may be impacted by exposure to each chemical in a mixture. The CMM has been significantly improved since its introduction more than 10 years ago. Major enhancements involve the expansion of the number of HCNs from 44 to 60 and inclusion of updated PAC values based on an improved development methodology and updates in the data used to derive the PAC values. Comparisons between the 1999 and 2009 versions of the CMM show potentially substantial changes in the assessment results for selected sets of chemical mixtures. In particular, the toxic mode hazard indices (HIs) and target organ HIs are based on more refined acute HCNs, thereby improving the quality of chemical consequence assessment, emergency planning and emergency response decision-making. Seven hypothetical chemical storage and processing scenarios are used to demonstrate how the CMM is applied in emergency planning and hazard assessment.
... Currently, 60 different HCNs are available for characterizing the potential target organ effects associated with exposure to a chemical (seeTable 1). This includes the addition of 16 new HCNs that were introduced in the 2008 version of the CMM including 13 new " acute effect " HCNs that were added to mirror the " chronic effect " HCNs used in earlier versions of the CMM (Craig et al., 2011; Yu et al., 2010). Because the CMM's HCN approach sums the HI's only for the chemicals that target the same or similar target organ systems, an assumption inherent in this approach is that the impacts of chemicals on distinctly different target organs do not influence each other. ...
... In recent years, the CMM's HCN-based approach has been improved by improving the assignment of HCN values for each of the approximately 3300 chemicals in the CMM data set. More detailed information on how the CMM works is presented in Yu et al. (2010) and in the supplementary material that accompanies this paper. Some users of the CMM have reported that the existing HCNbased approach may be overly conservative at times – not as overly conservative as computing the cumulative HI for all chemicals in the mixture – but still more conservative than it needs to be. ...
... Approach 1 applies a range of weighting factors to the top ten HCNs for each chemical in a mixture. The weighting factors are based on the priority ranking of the HCNs assigned to each chemical (seeTable 1) (Petrocchi et al., 2008; Yu et al., 2010). The implementation of Approach 1 involves ranking the HCNs for each chemical according to the priority order usingTable 1. Next, weighting factors are applied to each of the top 10 HCNs for a chemical. ...
Emergency preparedness personnel at U. S. Department of Energy (DOE) facilities use the chemical mixture methodology (CMM) to estimate the potential health impacts to workers and the public from the unintended airborne release of chemical mixtures. The CMM uses a Hazard Index (HI) for each chemical in a mixture to compare a chemical's concentration at a receptor location to an appropriate concentration limit for that chemical. This limit is typically based on Protection Action Criteria (PAC) values developed and published by the DOE. As a first cut, the CMM sums the HIs for all the chemicals in a mixture to conservatively estimate their combined health impact. A cumulative HI>1.0 represents a concentration exceeding the concentration limit and indicates the potential for adverse health effects. Next, Health Code Numbers (HCNs) are used to identify the target organ systems that may be impacted by exposure to each chemical in a mixture. The sum of the HIs for the maximally impacted target organ system is used to provide a refined, though still conservative, estimate of the potential for adverse health effects from exposure to the chemical mixture. This paper explores approaches to enhance the effectiveness of the CMM by using HCN weighting factors. A series of 24 case studies have been defined to evaluate both the existing CMM and three new approaches for improving the CMM. The first approach uses a set of HCN weighting factors that are applied based on the priority ranking of the HCNs for each chemical. The second approach uses weighting factors based on the priority rankings of the HCNs established for a given type of concentration limit. The third approach uses weighting factors that are based on the exposure route used to derive PAC values and a priority ranking of the HCNs (the same ranking as used in the second approach). Initial testing indicates that applying weighting factors increases the effectiveness of the CMM chemical mixtures in general, though care must be taken to avoid introducing non-conservative results. In the near future, additional testing and analysis will be conducted that may lead to the adoption of one of the tested approaches into the CMM.
Humans are simultaneously or sequentially exposed to many chemicals throughout their life, intentionally or unintentionally. These could include pesticides, pharmaceuticals, household products, and food additives. Individual control over exposure varies across personal, occupational, and environmental chemical exposure pathways. Personal lifestyle exposures such as firsthand tobacco smoke or alcohol are voluntary. Occupational exposure is “voluntary,” but the individual generally has less control over these exposures. On the other hand, individuals usually have few options for controlling environmental exposures under ordinary circumstances.
Gaseous emissions from municipal solid waste (MSW)disposal plants pose serious odor pollution and health risks. In this study, the emission of volatile organic compounds and carbon disulfide was compared in the main processing units of three disposal methods, i.e., landfilling, eco-mechanical biological treatment (EMBT)and anaerobic fermentation in a MSW disposal plant. Among the detected volatile compounds (VCs), the top ten odor compounds were methanethiol, dimethyl sulfide, dimethyl disulfide, carbon disulfide, styrene, m-xylene, 4-ethyltoluene, ethylbenzene, 2-hexyl ketone and n-hexane in the MSW disposal plant. Sulfur compounds were the main source of odor at the majority of sampling sites, and aromatic compounds were the dominant odor substrates at the tipping unit and sorting system of EMBT, while 2-hexanone was the major odor substrate at the tipping unit (AT)and sorting system (AS)of anaerobic fermentation and the landfill working surface. At AS and AT, the lifetime cancer risk values for 1,2-dichloroethane and trichloroethylene exceeded the carcinogenic risk value (>1.0E-04), and the hazard index values of naphthalene, trichloroethylene and acrolein all exceeded the acceptable level (>1). Therefore, special attention should be paid to VC emissions from MSW disposal facilities, and protection measures should be adopted for on-site workers to minimize health risks.
Environmental health risk assessments often involve assessing the potential health effects of exposure to multiple chemicals at once (i.e., complex mixtures). Because the possible number of chemical combinations is very large, few controlled in vivo toxicological studies with chemical mixtures are relevant or practical. In lieu of specific mixture toxicity data, the segregated hazard index (HI) approach has been used to determine if simultaneous exposures may warrant further investigation due to their combined adverse effects. Each chemical is assigned to one or more target organs based on critical effects; HIs for each target organ are generated by summing the individual hazard quotients for each of the chemicals assigned to that organ or organ system. To conduct this phased risk assessment approach in a consistent manner, a comprehensive, systematized list of toxicity targets for implementing this approach is needed. We present a comprehensive and standardized list of toxicity target organs and systems (TTOS), with example data sets, for consistent implementation of the segregated HI method. This method is designed to facilitate the standardization of the wide-spread use of the basic segregated hazard index approach. The basic hazard index mixtures screening (BHIMS) tool allows for rapid identification of exposure concerns that may warrant further and more sophisticated assessment. This article is protected by copyright. All rights reserved.
Short-term chemical concentration limits are used in a variety of applications, including emergency planning and response, hazard assessment and safety analysis. Development of emergency response planning guidelines (ERPGs) and acute exposure guidance levels (AEGLs) are predicated on this need. Unfortunately, the development of peer-reviewed community exposure limits for emergency planning cannot be done rapidly (relatively few ERPGs or AEGLs are published each year). To be protective of Department of Energy (DOE) workers, on-site personnel and the adjacent general public, the DOE Subcommittee on Consequence Assessment and Protective Actions (SCAPA) has developed a methodology for deriving temporary emergency exposure limits (TEELs) to serve as temporary guidance until ERPGs or AEGLs can be developed. These TEELs are approximations to ERPGs to be used until peer-reviewed toxicology-based ERPGs, AEGL or equivalents can be developed. Originally, the TEEL method used only hierarchies of published concentration limits (e.g. PEL- or TLV-TWAs, -STELs or -Cs, and IDLHs) to provide estimated values approximating ERPGs, Published toxicity data (e.g. LC50, LCLO, LD50 and LDLO for TEEL-3, and TCLO and TDLO for TEEL-2) are included in the expanded method for deriving TEELs presented in this paper. The addition here of published toxicity data (in addition to the exposure limit hierarchy) enables TEELs to be developed for a much wider range of chemicals than before. Hierarchy-based values take precedence over toxicity-based values, and human toxicity data are used in preference to animal toxicity data. Subsequently, default assumptions based on statistical correlations of ERPGs at different levels (e.g. ratios of ERPG-3s to ERPG-2s) are used to calculate TEELs where there are gaps in the data. Most required input data are available in the literature and on CD ROMs, so the required TEELs for a new chemical can be developed quickly. The new TEEL hierarchy/toxicity methodology has been used to develop community exposure limits for over 1200 chemicals to date. The new TEEL methodology enables emergency planners to develop useful approximations to peer-reviewed community exposure limits (such as the ERPGs) with a high degree of confidence. For definitions and acronyms, see Appendix. Copyright (C) 2000 Westinghouse Safety Management Solutions LLC obtained pursuant to US government contract.
Emergency Response Planning Guideline (ERPG) values are the only well-documented exposure limits developed to date specifically for use in evaluating the health consequences of exposure of the general public to accidental releases of extremely hazardous chemicals. Because ERPG values have so far been developed for relatively few chemicals, there is a need for alternative guidelines to be used for other chemicals. The objective of this work was to provide consistent methodology for the selection of reasonable interim values for these chemicals until such time as official ERPGs are developed. Most of the commonly available published and documented concentration-limit parameters were considered. ERPG values should be used as the primary guidelines for chemical emergency planning. Alternatives are recommended for use when ERPGs are not available. The parameters are to be used in the order presented, based on availability for the chemical of interest. Though these concentration limits were developed for different purposes, and were intended specifically for occupational use, no other options were available. Nonoccupational populations include the young, the aged, and other hypersensitive individuals. For each chemical, the adoption of alternatives to ERPGs should be carefully evaluated.
EPIcode (version 7.0) and ALOHA (version 5.2.3) are two of the designated toolbox codes identified in the Department of Energy's Implementation Plan for DNFSB Recommendation 2002-1 on Software Quality Assurance issues in the DOE Complex. Both have the capability to estimate evaporation rates from pools formed from chemical spills and to predict subsequent atmospheric transport and dispersion. This report provides an overview of the algorithms used by EPIcode and ALOHA to calculate evaporation rates and downwind plume concentrations. The technical bases for these algorithms are briefly discussed, and differences in the EPIcode and ALOHA methodologies highlighted. In addition, sample calculations are performed using EPIcode and ALOHA for selected chemicals under various environmental conditions. Side-by-side comparisons of results from sample calculations are analyzed to illustrate the impact that the different methodologies used by EPIcode and ALOHA have on predicted evaporation rates and downwind concentrations. It is recommended that the safety analyst explicitly evaluate the strengths and limitations of any code before selecting it for a specific application. User skill and expertise can often outweigh most of the differences between ALOHA and EPIcode. Recognizing that EPIcode is inherently a scoping tool, while ALOHA is based on more detailed models, the user is recommended to perform a parameter sensitivity study to determine major dependences in the applied model and to check code output with independent techniques, such as a hand calculation, alternative computer code application, or spreadsheet techniques. A multi-tiered approach of this type will provide better confidence in overall results than to unilaterally use one code alone without questioning. © 2006 Division of Chemical Health and Safety of the American Chemical Society.
In 1988, the Emergency Response Planning Guideline Committee was formed to review a series of documents summarizing chemical toxicity which had been developed by a combined interindustry effort. This Committee, is a part of the American Industrial Hygiene Association and is composed of representatives from academia, government and industry, with backgrounds in industrial hygiene, medicine and toxicology. Since its founding, the Committee has published 35 review documents containing recommendations for emergency exposure planning levels. Currently, the Committee is working on another 25. Most of the chemicals selected for this process are on the SARA Title III Extremely Hazardous Substance List or the OSHA Highly Hazardous Chemical List.
Emergency planning and hazard assessment of Department of Energy (DOE) facilities require consideration of potential exposures to mixtures of chemicals released to the atmosphere. Exposure to chemical mixtures may lead to additive, synergistic, or antagonistic health effects. In the past, the consequences of exposures to each chemical have been analyzed separately. This approach may not adequately protect the health of persons exposed to mixtures. This article presents default recommendations for use in emergency management and safety analysis within the DOE complex where potential exists for releases of mixtures of chemicals. These recommendations were developed by the DOE Subcommittee on Consequence Assessment and Protective Actions (SCAPA). It is recommended that hazard indices (e.g., HIi = Ci/Limiti, where Ci is the concentration of chemical "i") be calculated for each chemical, and unless sufficient toxicological knowledge is available to indicate otherwise, that they be summed, that is, sigma i(n) = 1HIi = HI1 + HI2 + ... + HIn. A sum of 1.0 or less means the limits have not been exceeded. To facilitate application of these recommendations for analysis of exposures to specific mixtures, chemicals are classified according to their toxic consequences. This is done using health code numbers describing toxic effects by target organ for each chemical. This methodology has been applied to several potential releases of chemicals to compare the resulting hazard indices of a chemical mixture with those obtained when each chemical is treated independently. The methodology used and results obtained from analysis of one mixture are presented in this article. This article also demonstrates how health code numbers can be used to sum hazard indices only for those chemicals that have the same toxic consequence.
Short-term chemical concentration limits are used in a variety of applications, including emergency planning and response, hazard assessment and safety analysis. Development of emergency response planning guidelines (ERPGs) and acute exposure guidance levels (AEGLs) are predicated on this need. Unfortunately, the development of peer-reviewed community exposure limits for emergency planning cannot be done rapidly (relatively few ERPGs or AEGLs are published each year). To be protective of Department of Energy (DOE) workers, on-site personnel and the adjacent general public, the DOE Subcommittee on Consequence Assessment and Protective Actions (SCAPA) has developed a methodology for deriving temporary emergency exposure limits (TEELs) to serve as temporary guidance until ERPGs or AEGLs can be developed. These TEELs are approximations to ERPGs to be used until peer-reviewed toxicology-based ERPGs, AEGL or equivalents can be developed. Originally, the TEEL method used only hierarchies of published concentration limits (e.g. PEL- or TLV-TWAs, -STELs or -Cs, and IDLHs) to provide estimated values approximating ERPGs. Published toxicity data (e.g. lc(50), lc(LO), ld(50) and ld(LO) for TEEL-3, and tc(LO) and td(LO) for TEEL-2) are included in the expanded method for deriving TEELs presented in this paper. The addition here of published toxicity data (in addition to the exposure limit hierarchy) enables TEELs to be developed for a much wider range of chemicals than before. Hierarchy-based values take precedence over toxicity-based values, and human toxicity data are used in preference to animal toxicity data. Subsequently, default assumptions based on statistical correlations of ERPGs at different levels (e.g. ratios of ERPG-3s to ERPG-2s) are used to calculate TEELs where there are gaps in the data. Most required input data are available in the literature and on CD ROMs, so the required TEELs for a new chemical can be developed quickly. The new TEEL hierarchy/toxicity methodology has been used to develop community exposure limits for over 1200 chemicals to date. The new TEEL methodology enables emergency planners to develop useful approximations to peer-reviewed community exposure limits (such as the ERPGs) with a high degree of confidence. For definitions and acronyms, see Appendix.
The primary purpose of the National Advisory Committee for Acute Exposure Guideline Levels for Hazardous Substances (NAC/AEGL) is to develop guideline levels for short‐term exposures to airborne concentrations for approximately 400 to 500 high priority, acutely hazardous substances within the next ten years. These Acute Exposure Guideline Levels (AEGLs) are needed for a wide range of planning, response, and prevention applications.
The NAC/AEGL Committee seeks to develop the most scientifically credible, acute (short‐term) exposure guideline levels possible within the constraints of data availability, resources and time. This includes a comprehensive effort in data gathering, data evaluation and data summarization; fostering the participation of a large cross‐section of the relevant scientific community; and the adoption of procedures and methods that facilitate consensus‐building for AEGL values within the Committee. The NAC/AEGL Committee is currently comprised of representatives of federal, state and local agencies, private industry and other organizations in the private sector that will derive programmatic or operational benefits from the existence of the AEGL values.
AEGL values are determined for three different health effect end‐points. These values are intended for the general public where they are applicable to emergency (accidental) situations. Threshold exposure values are developed for a minimum of 4 exposure periods (30 minutes, 1 hour, 4 hours, 8 hours). In certain instances, AEGL values for a 10‐minute exposure period also will be developed. Each threshold value is distinguished by varying degrees of severity of toxic effects, as initially conceived by the AIHA ERP Committee, subsequently defined in the NAS' National Research Council Report, Guidelines for Developing Community Emergency Exposure Levels for Hazardous Substances, published by the National Academy of Sciences in 1993, and further refined by the NAC/AEGL Committee. To date, the committee has reviewed over 80 chemicals.
Supplementary guidlines for the health risk assessment of chemical mixtures
- H Choudhury
- R Hertzberg
- G Rice
- J Gogliano
- D Mukerjee
- L Teuschler
- E Doyle
- Y Woo
- R Schoeny
- E Margosches
Choudhury H, Hertzberg R, Rice G, Gogliano J, Mukerjee D, Teuschler L, Doyle E, Woo Y, Schoeny R, Margosches E, and others. 2000. Supplementary guidlines for the health risk assessment of chemical mixtures. In: Agency EP, editor. Washington, DC: Federal Register
DOE G 151.1-2. Technical planning basis: Emergency management guide
DOE (US Department of Energy). 2007. DOE G 151.1-2. Technical planning basis: Emergency
management guide. https://www.directives.doe.gov/pdfs/doe/doetext/neword/151/g1511-
2.html/ [1 September 2009]
National Institute for Occupational Safety and Health)
NIOSH (National Institute for Occupational Safety and Health). 2008. Registry of Toxic Effects
of Chemical Substances (RTECS), Comprehensive Guide to the RTECS.
EPIcode. Version 7.0
- S Homann
Homann S. 2003. EPIcode. Version 7.0.
http://www.hss.energy.gov/nuclearsafety/qa/sqa/central_registry/EPIcode/EPI.htm [1
Lewis Dictionay of Toxicology
- Ra Lewis
Lewis, RA. 1998. Lewis Dictionay of Toxicology. 1 st Edition. Informa Healthcare.
Theory and rationale of industrial hygiene practice. Patty's industrial hygiene and toxicology
- Lj Cralley
- Lv Cralley
Cralley LJ and Cralley LV. 1985. Theory and rationale of industrial hygiene practice. Patty's
industrial hygiene and toxicology. 2nd ed. New York, Chichester, Brisbane, Toronto,
Singapore: John Wiley & Sons. p 150-185.
Derivation of temporary emergency exposure limits (TEELs)
- Craig
Subcommittee on Consequence Assessment and Protective Actions
- Scapa
ALOHA User's Manual. Version 5.4. US Environmental Protection Agency and National Oceanic and Atmospheric Administration
- Noaa Epa