Derivation of temporary emergency exposure limits (TEELs).

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.

Recommended default methodology for analysis of airborne exposures to mixtures of chemicals in emergencies.

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.