Identifying and Reducing Environmental Health Risks of Chemicals in Our Society Workshop Summary (2014) / Chapter Skim
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4 Models for Environmental Risk Assessment and Exposure Science
4 Models for Environmental Risk Assessment and Exposure Science
Pages 51-72
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From page 51... ...
; and a current project being conducted by the National Research Council (NRC) , the Design and Evaluation of Safer Chemical Substitutions: A Framework to Inform Government and Industry Decisions, which is intended to produce a consensus report that will be released in the fall of 2014.
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From page 52... ...
is really just hazard identification because we don't have the kind of robust information that is required in a risk assessment." So one question that must be asked is, How does one gather exposure assessment information that can help in the prioritization of regulatory decisions when there is not enough information for a full risk assessment? "I think that this [2009]
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From page 53... ...
To obtain clearer estimates of population risk -- the fifth bullet point -- it will be necessary to deal more effectively with uncertainty and variability in those estimates. One of the report's recommendations was that the EPA "should encourage risk assessments to characterize and communicate uncertainty and variability in all key computational steps -- for example, exposure assessment and dose–response assessment." In particular, Balbus said, the report recommended that "uncertainty and variability analysis should be planned and managed to reflect the needs for comparative evaluation of the risk management options." There was a great deal of discussion in the committee concerning how to determine the right amount of uncertainty analysis for the particular kind of assessment being undertaken, Balbus said.
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From page 54... ...
"A lot of the discussion in the committee was about recognizing these and identifying these and maybe thinking about them a little bit differently." A key default appears in site risk assessments where there are multiple different chemicals to which people are exposed. "If a particular chemical doesn't have sufficient information, it is by default assumed to have zero risk," Balbus said.
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From page 55... ...
The committee thought that the EPA's treatment of non-cancer and lowdose, nonlinear cancer end points is a major step in an overall strategy to harmonize cancer and noncancer approaches, Balbus said, but the committee also found that there are scientific and operational limitations to this approach. In particular, the committee focused on the issue of thresholds.
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There is a growing realization among environmental health professionals, Balbus said, that it is not sufficient to examine single-agent exposures in a vacuum. "You have to look at exposures in context -- not only in the context of co-exposures with other chemicals, but also in a context of multiple nonchemical stressors, whether that is psychological stress, nutritional stress, or socioeconomic stress." The committee recommended that the EPA should "draw on other approaches, such as those from ecological risk assessment and social epidemiology, to incorporate interactions between chemical and nonchemical stressors in assessments." In the short term, the EPA should "develop databases and default approaches to allow for incorporation of key nonchemical stressors in cumulative risk assessments in the absence of population-specific data, considering exposure patterns, contributions to relevant background processes, and interactions with chemical stressors."
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"The other piece was imbedding risk assessment in a decision framework that considers the question that has to be answered and the choices that have to be made," he said. "For example, in green chemistry if you have a multitude of different kinds of chemicals that you could be using other than your chemical of concern, that would be a very different risk assessment than if you only have that one chemical to serve a particular function." Thus, the committee recommended that the EPA "adopt a framework for risk-based decision making that embeds the Red Book risk-assessment paradigm into a process with initial problem formulation and scoping, up front identification of risk-management options, and use of risk assessment to discriminate among these options." EXPOSURE SCIENCE IN THE 21ST CENTURY: A VISION AND A STRATEGY The second speaker was Paul Gilman, senior vice president and chief sustainability officer at Covantra.
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. On ne of the maiin focuses off the study waas the variouus scientific annd technoological advances that hav ve emerged in recent yeaars that can be applied d to exposu ure science.
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Thhese emerging g technologiees combined w with a growinng appreciation for thee power of exxposure analyysis make expposure sciencce "a place thhat we might think of asa an emerginng frontier andd one that shoould be focussed on," Gilman G said. The T committee laid out a vision of exxposure sciennce that is moving from m the historiccal focus on discrete expoosure to a new, broadeer focus that considers c exposures • "from sourcce to dose; • me, space, annd on multiple levels of integration ((including tim biologic scaale)
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It is a 20-year program of trying to know everything about everything for an organism and all of the organisms that affected it because certainly we were stressing putting people in an ecological context as well." With those difficulties in mind, the committee identified two overarching research needs in the area of exposure science: • "Characterizing exposures quickly and cost effectively at multiple levels of integration -- including time, space, and biologic scales -- and for multiple and cumulative stressors, and • Scaling up methods and techniques to detect exposure in large human and ecologic populations of concern" (NRC, 2012)
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The EPA is joined in the effort by a number of partners, including the National Institute of Environmental Health Science, the National Toxicology Program, the Department of Defense Army Corps of Engineers, the Food and Drug Administration National Center for Toxicologic Research, the National Institute of Occupational Safety and Health, Health Canada, the California Environmental Protection Agency, the European Chemical Agency, and the European Community Joint Research Commission. The NexGen effort started with a review of the recommendations in several earlier reports, including Toxicity Testing in the 21st Century (NRC, 2007)
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Hence, from discussions with decision makers and reviews of the available data, prototype concepts were developed that could support different decision contexts. • A draft strategic framework that articulated guiding principles for NexGen prototypes development was also developed.
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These prototypes are the proof-of-concept assessments that focused on "reverse engineering" from known public health risks to NexGen-type risk assessments, thus verifying the use of new approaches by comparison with robust traditional data. The first three prototypes examined the connections among benzene, other leukemogens, and leukemia; between ozone and lung inflammation; and between polycyclic aromatic hydrocarbons and lung cancer.
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From page 64... ...
Cote noted that what the NexGen project intended to do was iterate back and forth between the new types of data, such as omic data and cell biology data, and the traditional data to understand what could and could not be done, sort out what information was most valuable, and begin to develop decision rules that would help the EPA use new types of data consistently and appropriately to get the "right answer." Several important points were illustrated by these major assessment prototypes, said Cote.
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From page 65... ...
Of the key issues raised in Toxicity Testing in the 21st Century and Science and Decisions, the NexGen report (EPA, 2013) discusses how the agency might proceed on a number of issues, including matching assessments to decision context, harmonization of cancer and noncancer approaches, better characterization of population variability, cumulative risks from mixtures and other environmental stressors, and improved assessment of responses at environmental exposure levels.
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"I think that integrating what we know about human disease and human genetics that comes out of the study of disease in the absence of chemical exposure with data on the effects of chemical exposures .
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"We had Thaddeus Schug from NIEHS talk about tiered endocrine disruption processes and testing," Shelton-Davenport continued. Robert Tanguay and Jim Hutchison spoke about the importance of using simple 5 Further information on the Design and Evaluation of Safer Chemical Substitutions: A Framework to Inform Government and Industry Decisions is available at http://www8.nationalacademies.org/cp/projectview.aspx?
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From page 68... ...
They differ, for instance, in how they consider health and safety effects versus ecological risks, such as aquatic toxicity or the environmental impacts of chemicals, when they are comparing alternatives. "To give an example," she said, "Cradle to Cradle is one that includes everything from environmental impact, as in greenhouse gases and water use, to social fairness.
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From page 69... ...
The committee is also charged with developing at least two examples that "demonstrate how the framework can be applied by different users in contrasting decision contexts with diverse priorities." According to the statement of task, these examples "shall include demonstration of how high-throughput and high-content data streams could inform assessment of potentially safer substitutes early in the chemical development process." DISCUSSION Lynn Goldman noted that there have been many recent scientific advances with implications for risk assessment and exposure assessment. Will these scientific advances translate into faster, more efficient assessments?
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"The title is Evaluation of Safer Chemical Substitutions, but my thinking is that they are likely going to be having a broader discussion." Gina Solomon of the California Environmental Protection Agency also weighed in on the issue. "In the California Safer Consumer Products Regulations, we have devised an off-ramp where if the state identifies a chemical of concern in a product and lists it, the manufacturer of that product may either perform an alternatives analysis or may simply take the chemical out of the product, and then that would save them the trouble of having to go through the entire alternatives analysis.
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From page 71... ...
of risk assessment: public dialogue conference. Washington, DC: EPA.
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