Aggregate and Cumulative Exposures

An understanding of the various routes of exposure for chemicals in products, as well as their interaction with similar chemicals, are an important element of REACH and will likewise be central to a reformed TSCA. In combination with data on health effects, this information will allow authorities to make required safety determinations. Reliable modeling of exposure scenarios will also equip companies to persuasively defend their products against unfounded accusations in the media, the internet and the courts.

********

An influential 1994 National Academy of Sciences report called Science and Judgment in Risk Assessment was one of the first voices citing aggregate and cumulative chemical exposures as critical to understanding real-world risk. Aggregate and cumulative exposures are related concepts concerning the potential impact of a given chemical through multiple routes of exposure, as well as the possibility that multiple chemicals might interact to produce additive or synergistic effects. For example, a person might be exposed to mercury from a smelting plant, but also in the fish he consumers. The same person might be exposed to different substances that share mercury’s neurotoxic effects, for example in pesticides he uses in the garden.

The Lautenberg bill directs EPA to “consider” the work of the Academy in this area. H.R. 5820 goes further, directing EPA to incorporate aggregate exposures in its determination of “reasonable certainty of no harm” (RCNH) for a particular chemical. At the July 29 hearing, there was some disagreement among witnesses and subcommittee members whether EPA or the chemical manufacturer or processor bore the ultimate responsibility for examining and making judgments on these complex issues.

Several lawmakers, including Rep. Diana DeGette (D-CO) noted that a recent modification to the bill agreed to by its drafters would make the company responsible only for providing information on exposure related to the chemical’s “intended use.” The agency would then amalgamate company submissions on various uses and exposures and incorporate these into its safety determination. However, other sections of the bill make clear that the agency’s failure to make timely determinations can have the effect of keeping a chemical out of the marketplace. Consequently, if EPA is thwarted in its efforts by the complexity of the analysis, by resource constraints or other factors, producers, formulators and commercial users may well have to undertake this effort themselves in order to keep the substance in use.

Regardless of what TSCA eventually requires, we believe there are compelling reasons for companies involved in the production and use of chemicals to take a proactive approach to exposure modeling and life-cycle analysis. Exposure data is a necessary complement to data on human and ecological toxicity in the realm of product stewardship and defense. Given the ready access to information from a variety of media sources and the ease with which this information can be distorted or misunderstood, a company’s ability to substantiate its exposure, hazard and disposal findings will prove critical in defending a product, company or industry. The groundswell of toxic torts cases, along with state-initiatives to restrict or eliminate chemicals based on inaccurate data, further support the wisdom of building a baseline understanding of exposure. We believe there’s no need to wait for legislation, news coverage or litigation to begin assembling one's product defense arsenal.