Williams C A, Jones H D, Freeman R W, Wernke M J, Williams P L, Roberts S M, James R C
TERRA, Inc., Tallahassee, Florida 32303, USA.
Regul Toxicol Pharmacol. 1994 Dec;20(3 Pt 1):259-80. doi: 10.1006/rtph.1994.1076.
Reference doses (RfDs) and reference concentrations (RfCs) developed by the United States Environmental Protection Agency (USEPA) are typically used in the quantitation of risk of potential adverse human health effects from exposure to environmental chemicals. For a large number of chemicals, however, USEPA RfDs and RfCs have not yet been determined. Thus, for risk assessments that involve a large number of chemicals, there is insufficient toxicity information with which to evaluate potential adverse human health effects for all chemicals present at a particular site. Due to this insufficiency, the risk assessor must either (1) ignore potential exposures on the assumption that omitting these exposures does not significantly alter decisions concerning the remediation of the site or (2) undertake a lengthy and costly analysis to generate the necessary RfDs or RfCs. A potential solution to this problem is to develop estimated permissible concentrations (EPCs), values which represent permissible environmental concentrations or related acceptable daily dosages derived from occupational exposure limits. In the present analysis, acceptable daily dosages determined using the EPC method were compared to USEPA RfDs or RfCs which were converted to dosages based on standard exposure assumptions. Based on a comparative analysis of EPCs and USEPA reference values for 103 chemicals, it was found that EPC daily dosages represent a reasonably conservative surrogate value when USEPA or state reference values are unavailable. Given that there are hundreds of chemicals with occupational exposure limits but no state or USEPA reference values, acceptance of the EPC methodology would provide an interim solution for the problem of insufficient toxicity information for a substantial number of environmental chemical contaminants.
美国环境保护局（USEPA）制定的参考剂量（RfDs）和参考浓度（RfCs）通常用于定量评估接触环境化学品对人类健康造成潜在不良影响的风险。然而，对于大量化学品而言，USEPA的RfDs和RfCs尚未确定。因此，在涉及大量化学品的风险评估中，缺乏足够的毒性信息来评估特定场所存在的所有化学品对人类健康的潜在不良影响。由于这种信息不足，风险评估人员必须要么（1）假定忽略这些暴露不会显著改变有关该场所修复的决策，从而忽略潜在暴露；要么（2）进行冗长且成本高昂的分析以生成必要的RfDs或RfCs。解决这一问题的一个潜在办法是制定估计允许浓度（EPCs），即从职业接触限值得出的代表允许环境浓度或相关可接受日剂量的值。在本分析中，将使用EPC方法确定的可接受日剂量与根据标准暴露假设转换为剂量的USEPA RfDs或RfCs进行了比较。基于对103种化学品的EPCs和USEPA参考值的比较分析，发现当USEPA或州参考值不可用时，EPC日剂量代表了一个相当保守的替代值。鉴于有数百种化学品有职业接触限值，但没有州或USEPA参考值，采用EPC方法将为大量环境化学污染物毒性信息不足的问题提供一个临时解决方案。
