Environmental Risk Assessment of New Chemicals Under the Toxic Substances Control Act TSCA Section Five

The Toxic Substances Control Act (TSCA) allows for the regulation of new industrial chemicals if a chemical may present an unreasonable risk toward the environment, or if a chemical has significant exposure toward the environment. Risk assessment under TSCA Section 5 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 toward organisms in the environment, and toward 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 on a given organism at a known concentration of chemical. Effective concentrations can be based on test data or predicted using structure activity relationships (SAR). A collection of all of the ECs for a chemical is called a hazard profile or a toxicity profile. Environmental factors which reduce the inherent toxicity of a chemical (that is, mitigation factors), as well as, enhancement factors that increase toxicity are taken into account when the hazard profile is developed. The environmental-exposure assessment consists of 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 Percen-tile Stream Flow Method and the Probability Dilution Model (PDM) Method. Environmental-risk assessment is done by using the quotient method. This method simply compares an EC or a concern concentration (CC) to the actual or predicted environmental concentrations (PEC). If the PEC is greater than the EC or CC, then you have a potential risk. Case studies for several types of chemicals will be presented: neutral organic chemicals; organic chemicals with excess toxicity; anionic surfactants; nonionic surfactants; cationic surfactants; amphoteric surfactants; anionic polymers; nonionic polymers; poly cationic polymers; amphoteric polymers; acid dyes; neutral dyes; cationic dyes; amphoteric dyes; polyanionic monomers; and compounds which hydrolyze (for example, acid chlorides and alkyloxysilanes); and metals.