The U.S. Environmental Protection Agency (EPA) announced on January 4, 2013, the availability of the first draft risk assessments developed under the Toxic Substances Control Act (TSCA) Work Plan. The draft risk assessments are for particular uses of five chemicals found in household products: methylene chloride or dichloromethane (DCM) and N-methylpyrrolidone (NMP) in paint stripper products; trichloroethylene (TCE) as a degreaser and a spray-on protective coating; antimony trioxide (ATO) as a synergist in halogenated flame retardants; and 1,3,4,6,7,8-hexahydro-4,6,6,7,8,8,-hexamethylcyclopenta-[γ]-2 -benzopyran (HHCB) as a fragrance ingredient in commercial and consumer products. A Federal Register notice signed by Wendy C. Hamnett, Director of EPA’s Office of Pollution Prevention and Toxics (OPPT), on January 3, 2013, announces public availability of the risk assessments and upon its publication will begin a 60-day comment period. In the notice, EPA requests nominations of expert peer reviewers within 30 days of the opening of the public comment period. EPA will forward the nominations to the independent peer review contractor setting up the individual peer review panels. The pre-publication version of the notice is available online. More information on and copies of the draft risk assessments are available online.
EPA states the draft assessments focus either on human health or ecological hazards for specific uses that are subject to TSCA regulation. Three of the draft risk assessments — DCM, NMP, and TCE — indicate a potential concern for human health under specific exposure scenarios for particular uses. The draft assessments for ATO and HHCB indicate a low concern for ecological risks. If EPA concludes in the final risk assessments that there is a potential for concern, EPA states that it will take appropriate action to address possible risks.
The pre-publication Federal Register notice includes the following information on the draft risk assessments:
- HHCB: HHCB is a synthetic polycyclic musk used as an ingredient in a wide range of consumer products, including perfumes, cosmetics, shampoos, lotions, detergents, fabric softeners, and cleaning agents. The draft assessment focuses on environmental risk due to release of HHCB to the aquatic and terrestrial environment from all combined uses. Human health risks have been evaluated previously and are summarized in the draft assessment.
For HHCB, EPA is asking for nominations of peer reviewers who are experts in the following areas: aquatic ecotoxicology, terrestrial ecotoxicology, fate and biodegradation, fate and bioaccumulation, environmental risk assessment (aquatic and terrestrial), and analytical chemistry of organic waste water contaminants.
- TCE: The draft assessment focuses on uses of TCE as a degreaser and in consumer products used by individuals in the arts/crafts field. Given the range of endpoints (cancer; non-cancer, including potential effects on the developing fetus), the susceptible populations addressed are children and adults of all ages (including pregnant women). Thus, the draft assessment focuses on all human lifestages.
For TCE, EPA is asking for nominations of peer reviewers who are experts in the following areas: toxicology of TCE (developmental cardiotoxicity, immunotoxicology, reproductive toxicology, and cancer biology), expertise in physiologically based pharmaco-kinetics (PBPK) modeling for TCE, exposure of volatile organics, experts on use of volatiles as solvent degreasers and in the arts/crafts field, chemical/environmental risk assessment experts, and experts familiar with environmental release data and associated modeling/interpretation.
- ATO: The draft assessment focuses on the ecological hazards that may be associated with ATO use in flame retardants. Human health risks for the flame retardant use have been evaluated previously and are summarized in this draft assessment. Because ATO use in plastics was previously evaluated for human health and the environment, that use scenario is not evaluated.
For ATO, EPA is asking for nominations of peer reviewers who are experts in the following areas: exposure modeling, aquatic ecotoxicology, terrestrial ecotoxicology, inorganic chemistry addressing water and sediment issues, and ground water.
- DCM and NMP: The related draft assessments focus on the use of DCM and NMP in paint stripping and will be addressed by the same peer review panel. With regard to DCM, the draft assessment focuses on inhalation exposure to consumers and workers, and addresses human health concerns for both cancer and non-cancer effects. The low concern for environmental effects of DCM is discussed in the draft assessment. With regard to NMP, the draft assessment focuses on acute and chronic inhalation and dermal exposure to consumers and workers in the paint stripping use and the endpoint of concern is developmental toxicity. The low concern for environmental effects of NMP is discussed in the draft assessment.
For DCM and NMP, EPA is asking for nominations of peer reviewers who are experts in the following areas: inhalation toxicology, toxicokinetics/PBPK modeling, dermal toxicology, neurotoxicology, immunotoxicology, developmental and reproductive toxicology, cancer biology, expertise in U.S. consumer modeling (inhalation and dermal), and expertise in occupational exposure assessment (inhalation and dermal), especially as related to volatile organic chemicals.
EPA states that the draft risk assessments on the two remaining chemicals from the initial group of seven Work Plan chemicals scheduled to begin assessment in 2012 — the long- and medium-chain chlorinated paraffins — are on a different schedule for completion. EPA will make the draft risk assessments available for public comment through another Federal Register notice issued on a later date.
Next Steps
EPA states that it will publish the list of candidate peer reviewers, which will include those nominated by the public and those identified by a contractor, in the Federal Register for public comment. After a 30-day comment period, informed by any comments, the contractor will select the peer reviewers for these “influential” risk assessments. The detailed Peer Review Plans for the draft assessments are accessible through the EPA’s Peer Review Agenda website. EPA will consider comments received from the public and the subsequent peer review when preparing the final individual chemical risk assessments and will describe in a written report how it addressed public and reviewer comments in the final assessments. EPA will issue another Federal Register notice to announce the availability of the final risk assessments.
Commentary
Based on a quick skim, the human health risk assessments seem to be clearly and carefully presented. They also seem to be quite conservative in the approaches applied and the conclusions obtained. One could argue that such conservatism, while appropriate for a preliminary or screening-level risk assessment, may inappropriately overstate the risk conclusions and their significance given that these assessments are intended to be followed by “appropriate risk reduction actions” if potential risks of concern are determined to exist. Because of the detail provided, the bases for EPA’s health risk conclusions are clearly set forth. This level of detail may also be seen to provide multiple “hand-holds” for raising issues with and contesting EPA’s judgments as it constructed its assessments and outlined its conclusions. While EPA seems to have done a good job of identifying and discussing the uncertainties in its assessments, as noted above it also seems to have consistently opted for conservative, worst-case assumptions and approaches. The results of the peer review and its reaction to EPA’s approach will be an important development to watch, both for purposes of these assessments and for signaling whether a more refined and realistic approach is suggested for future Work Plan risk assessments.
Overall, this would appear to be the next step in the continued “TSCA revitalization” effort of the current Office of Chemical Safety and Pollution Prevention (OCSPP) leadership, especially as articulated by Mr. Jim Jones, Acting Assistant Administrator. These assessments, while conservative, will place a marker in terms of what OPPT believes to be is the best risk assessment estimate given the state of knowledge they have about hazard and exposure. Should an interested party claim that the risk estimates are unreasonable overestimates, it will be their burden to supplement the current record so that OPPT can revise its assessments and perhaps reach a different conclusion.
This is intended to, in part, improve on past practices where often incomplete or missing information was identified and then any follow-up was left to an uncertain fate. Separately, it will remain to be seen whether any new approach can result in more meaningful generation of additional data or enhance regulatory conclusions made by the program.
Another issue that has been raised concerns the adequacy of the peer review that EPA plans to conduct on what it believes to be “influential” draft risk assessments. On December 21, 2012, Senator James Inhofe (R-OK), Ranking Member of the Senate Environment and Public Works Committee, and Committee Members Senators Lamar Alexander (R-TN), Mike Crapo (R-ID), and David Vitter (R-LA) requested EPA classify the risk assessments prepared under the TSCA Work Plan as “highly influential.” Because EPA chose to classify them as “influential,” the Senators noted that they would be subject to a less rigorous peer review. The Senators cite the Office of Management and Budget (OMB) 2004 Final Information Quality Bulletin for Peer Review and EPA’s Peer Review Handbook, which state that highly influential scientific assessments are those that are “novel, controversial, or precedent-setting” or that have significant interagency interest.
The Senators recommended that, to ensure a “robust body of reviewers,” EPA encourage the public to nominate peer review candidates. In addition, consistent with the best practices of the National Academies and EPA’s Science Advisory Board, EPA should allow the public to comment on the specific peer reviewers under consideration. The Senators also criticized EPA’s plan to conduct the peer reviews by teleconference, and encouraged EPA to respond to public comments in writing.
While EPA will solicit nominations from the public for peer review candidates and allow comment on specific peer reviewers, it appears that EPA does not intend to follow all the Senators’ recommendations. Based on language in the draft risk assessments, it seems EPA has decided to continue to classify the risk assessments as “influential” scientific assessments and not to conduct any peer review sessions in person. Each draft risk assessment states: “A peer review panel is being arranged for this influential workplan assessment product based upon need and following Agency peer review guidance. The format will be a teleconference of an ad hoc panel meeting consisting of independent experts.” How this aspect plays out will also be very telling regarding EPA’s future approach to Work Plan risk assessments.