Exposure response regulatory considerations

In estimating the cumulative risk of a chemical in LCA, dose-response extrapolations can be based on toxicological benchmarks. Such a benchmark approach is considered more appropriate for use in comparative assessment contexts, such as in an LCA study. Benchmarks are an exposure measure associated with a consistent change in response, such as the 10% or even the 50% effect level. Regulatory-based measures do not necessarily provide a consistent risk basis for comparison, as they were often never developed for use in such a comparative context or to facilitate low dose-response extrapolation. Other data differences include the use of median, rather than extreme, data in the fate and exposure modeling, as well as the consideration of safety factors only as part of the uncertainty assessment and not as an integral part of the toxicological effects data. 

Complete assessment of hazards should be made for all materials and suspected products associated with the experiment or procedure. Chapter 3 provides the basis for interpreting and applying much of the available hazard information. Both literature resources and knowledgeable contacts inside the local research community and in other institutions can provide additional information. If risks are determined to be unacceptable, experiments can be redesigned to minimize the volumes of chemicals used or to employ less hazardous alternatives that might do the job equally well. Some important considerations include volumes and flow rates to be employed, amounts required, physical properties of materials to be used, potential for exposure, regulatory concerns, and emergency response for unexpected events. 

The question of the vaUdity of adherence to bifurcated dose—toxic response relationships remains one for nonoccupational adult and childhood Pb exposures and one for workers exposed to Pb. Evidence continues to accumulate for persisting neurotoxic and other adverse outcomes in adults at workplace Pb exposure levels considerably below regulatory levels now in place for removal and retorn. 

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