Williams C A, James R C, Freeman R W
TERRA, Inc., Tallahassee, Florida 32303, USA.
Regul Toxicol Pharmacol. 1995 Aug;22(1):64-75. doi: 10.1006/rtph.1995.1070.
Reference doses (RfDs) and reference concentrations (RfCs) developed by the United States Environmental Protection Agency (USEPA) are typically used to assess the risk of potential adverse human health effects from exposure to environmental chemicals. For a large number of chemicals, however, USEPA RfDs or RfCs have not yet been determined. Thus, for risk assessments that involve a large number of chemicals, there may not be USEPA- or state-derived toxicity constants for all chemicals present at a particular site. A potential solution to this problem is to use estimated permissible concentrations (EPCs) to develop acceptable daily dosages from occupational exposure limits. The EPC is defined as the concentration of a chemical which, under continuous exposure conditions, is expected to be devoid of all acute and chronic toxicities. EPC values are based on allowable occupational exposure limits such as threshold limit values (TLVs), which are workplace exposure guidelines suggested by the American Conference of Governmental Industrial Hygienists. In the present analysis, the EPC method was used to develop interim toxicity constants for more than 30 chemicals which possess TLVs and which appear in the Appendix VIII Hazardous Constituents list, but for which the USEPA has not yet assigned a current RfD or RfC. Appendix VIII chemicals are commonly found at hazardous waste and other sites. Consequently, the development of toxicity constants for the more than 30 chemicals on this list would prove to be most useful for risk assessment purposes. These toxicity constants were then used, together with standard exposure assumptions, to develop acceptable human health-based soil and water concentrations for these chemicals. The use of these values as interim guidance would therefore allow individuals responsible for assessing human health effects posed by environmental contamination to address all site chemicals without performing extensive, chemical-specific toxicological analyses.
美国环境保护局（USEPA）制定的参考剂量（RfDs）和参考浓度（RfCs）通常用于评估接触环境化学品对人类健康产生潜在不良影响的风险。然而，对于大量化学品，USEPA尚未确定其RfDs或RfCs。因此，对于涉及大量化学品的风险评估，特定场所存在的所有化学品可能没有USEPA或各州得出的毒性常数。解决这一问题的一个潜在办法是使用估计允许浓度（EPCs），根据职业接触限值来制定可接受的每日剂量。EPC被定义为在持续接触条件下预计不会产生所有急性和慢性毒性的化学品浓度。EPC值基于诸如阈限值（TLVs）等允许的职业接触限值，阈限值是美国政府工业卫生学家会议建议的工作场所接触指南。在本分析中，EPC方法用于为30多种具有TLVs且出现在附录VIII危险成分清单中但USEPA尚未指定当前RfD或RfC的化学品制定临时毒性常数。附录VIII中的化学品常见于危险废物和其他场所。因此，为该清单上的30多种化学品制定毒性常数对于风险评估将非常有用。然后，这些毒性常数与标准接触假设一起用于为这些化学品制定基于人类健康的可接受土壤和水浓度。因此，将这些值用作临时指南将使负责评估环境污染对人类健康影响的人员能够处理所有场地化学品，而无需进行广泛的、针对特定化学品的毒理学分析。
