Environmental Protection Agency definitions, differences

The US Environmental Protection Agency (USEPA 1998) describes problem formulation as an iterative process with 4 main components integration of available information, definition of assessment endpoints, definition of conceptual model, and development of an analysis plan. These 4 components apply also to probabilistic assessments. In addition, it is useful to emphasize the importance of a 5th component dehnition of the assessment scenarios. The relationships between all 5 components are depicted in Figure 2.1. Note that the bidirectional arrows represent the interdependency of the different components and imply that they may need to be revised iteratively as the formulation of the problem is rehned. 

The United States of America in 1998 announced the Chemical Right-to-Know (RTK) Initiative46 which was the US government response to an Environmental Protection Agency (EPA) study that found that very little basic toxicity information is publicly available on most of the HPV chemicals made and used in the USA. It should be noted that the US definition of UPV chemicals is different from that used in the rest of the world, as the US definition is a chemical produced in or imported into the US A in amounts... 

Under the Toxic Substances Control Act (TSCA), numerous nomenclature issues have arisen over the years, some of which have been discussed in this book. There will undoubtedly be new nomenclature issues to be resolved, nanoparticles being a current case in point. Issues of the past have often arisen out of administrative and sometimes arbitrary naming conventions, but risks associated with chemical substances do not depend on how they are named. Nanoparticles present different issues in the sense that the Environmental Protection Agency (EPA) stated that the TSCA regulates chemical substances of a particular molecular identity, without regard to physical properties such as size and shape. Potential for significant risk due to nanoparticles clearly exists exactly due to those physical properties. Regulators and interpreters of the TSCA must address potential risks such substances may pose even if their non-nano counterparts do not, and even if their newness does not meet the current definition of substances with different molecular identities. 

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