Nabholz J V
Office of Toxic Substances (TS-796), United States Environmental Protection Agency, Washington, DC 20460-0001.
Sci Total Environ. 1991 Dec;109-110:649-65. doi: 10.1016/0048-9697(91)90218-4.
The Toxic Substances Control Act (TSCA) was enacted in 1976 and provides for the regulation of industrial chemicals. TSCA allows for regulation of a chemical if there is an unreasonable risk towards human health or the environment, and it allows for testing if a chemical may present an unreasonable risk or has significant exposure towards humans or the environment. Risk assessment under TSCA consists of the integration of the hazard assessment for a chemical with the chemical's exposure assessment. The environmental hazard assessment consists of identifying all of the effects of a chemical towards organisms in the environment, and towards the populations, communities, and ecosystems to which those organisms belong. Toxicity data for a chemical consists of effective concentrations (EC) which indicate the type of effect and the seriousness of that effect at a known concentration of chemical. Effective concentrations are either measured or predicted using structure activity relationships (SAR). SAR may consist of nearest analog analysis, member of a toxic chemical class, or quantitative SAR (QSAR). A collection of all of the ECs for a chemical is called a hazard profile or a toxicity profile. The environmental exposure assessment consists of measuring or predicting the environmental concentrations of a chemical from releases due to its production, processing, uses, and disposal. There are two types of exposure assessment most frequently used under TSCA: the Percentile Stream Flow Method and the Probability Dilution Model (PDM) Method. Environmental risk assessment under TSCA is performed by using the quotient method. This method simply compares an EC with the actual or predicted environmental concentrations (PEC). If the PEC is greater than the EC, then you have a potential risk. The risk assessment process usually consists of three steps: (i) worst case risk assessment, (ii) identification of the type or risk (e.g., acute and/or chronic risk), and (iii) quantification of the degree of environmental risk or the potential environmental impact expected for each type of risk. If the risk assessment determines that a chemical presents a potential risk to the environment, then the results of this assessment are integrated with the economic assessment, any relative risk factors, and governmental policy in order to decide whether a chemical may present an unreasonable risk to the environment.
《有毒物质控制法》（TSCA）于1976年颁布，规定了对工业化学品的监管。如果某种化学品对人类健康或环境存在不合理风险，TSCA允许对其进行监管；如果某种化学品可能存在不合理风险或对人类或环境有重大暴露，则允许进行测试。TSCA下的风险评估包括将化学品的危害评估与化学品的暴露评估相结合。环境危害评估包括确定化学品对环境中生物的所有影响，以及对这些生物所属的种群、群落和生态系统的影响。化学品的毒性数据由有效浓度（EC）组成，有效浓度表明在已知化学品浓度下效应的类型和严重程度。有效浓度可通过测量或使用构效关系（SAR）进行预测。SAR可能包括最相近类似物分析、有毒化学品类别成员或定量构效关系（QSAR）。某种化学品所有EC的集合称为危害概况或毒性概况。环境暴露评估包括测量或预测化学品因生产、加工、使用和处置而释放到环境中的浓度。TSCA下最常使用的两种暴露评估类型是：百分位数流量法和概率稀释模型（PDM）法。TSCA下的环境风险评估通过商数法进行。该方法只需将EC与实际或预测的环境浓度（PEC）进行比较。如果PEC大于EC，则存在潜在风险。风险评估过程通常包括三个步骤：（i）最坏情况风险评估，（ii）确定风险类型（例如，急性和/或慢性风险），以及（iii）量化每种风险类型预期的环境风险程度或潜在环境影响。如果风险评估确定某种化学品对环境存在潜在风险，则将该评估结果与经济评估、任何相关风险因素和政府政策相结合，以决定该化学品是否可能对环境构成不合理风险。
