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Just a few short weeks after the U.S. Environmental Protection Agency (EPA) released its revised draft methanol assessment under the Integrated Risk Information System (IRIS), the Agency quickly issued a finalized assessment.
While everyone agrees that the Agency needs to complete assessments in a timely manner, the release of the final assessment so quickly after the draft raises a number of questions. More specifically, EPA missed an important opportunity in the final methanol assessment to demonstrate how it incorporates the recommendations from its independent peer review panel charged with making sure the Agency makes sound scientific judgments.
The methanol assessment has important ramifications for the overall utility of assessments in protecting public health and for the ongoing effort to improve how chemical risk assessments are conducted under the IRIS program.
Methanol can be detected in anyone who consumes a healthy daily portion of vegetables, fruits, and juices, all of which contain trace amounts of methanol. Methanol is also a natural byproduct in the body, produced as a result of normal cellular metabolism and enzymatic activity.
Separately, methanol serves many important functions in the world outside of our bodies. It is a building block for hundreds of chemicals that touch our daily lives, from paints and plastics to furniture and carpeting. As a recent editorial in the Wall Street Journal reveals, methanol also holds great potential as an emerging energy resource for fueling cars, power turbines, and fuel cells.
Because methanol is present inside our bodies (endogenously) as a naturally occurring substance and since we interact with trace levels of methanol through everyday exposure outside of our bodies (exogenously), it is important that EPA take both into consideration when assessing the toxicity of the substance.
In June, EPA conducted a peer review and provided an opportunity for public comment on the Agency’s revised draft toxicological review of methanol. ACC was one of the groups that provided constructive feedback for EPA to take into account before publishing its final assessment.
Although EPA considered and responded to comments, the Agency ultimately chose to disregard many of the recommendations expressed by the independent peer review panel and failed to act on issues raised in the public comments.
The key issue raised by the independent peer reviewers centers on the poor scientific judgment EPA employed for developing proposed toxicity values for methanol. EPA failed to accurately portray potential human health risks and, in fact, overestimated methanol’s potential health risks at environmentally relevant exposures.
The Agency went wrong in two areas:
1. The Science: In setting toxicity values for methanol, the Agency failed to properly differentiate between potential exposure from external sources and the exposures that occur from methanol in our bodies and from the ingestion of naturally-occurring methanol from fruits, vegetables, and juices. The Agency has essentially proposed “unsafe” exposure levels that are well within the normal background levels of methanol Americans may carry from following the USDA recommendations for a healthy diet.
EPA claims this is simply a more conservative route to assess toxicity. Unfortunately, EPA’s approach is simply a shortcut to complete a very complex risk assessment. But there are no shortcuts to sound science – the Agency needed to address both endogenous and exogenous exposures to methanol.
2. The Lack of Criteria for Study Selection: In 2011 the National Academy of Sciences (NAS) clearly recommended that EPA develop transparent and clear guidelines for study selection that include the evaluation of the strengths and weaknesses of studies. EPA has yet to develop these criteria, and the shortcomings of this approach are made clear in the IRIS methanol assessment.
In one portion of the final assessment, EPA says that a certain study (NEDO, 1987) had “multiple reporting deficiencies and data gaps” and, as recommended by an earlier review, should be used only in a descriptive manner. However, instead of following peer reviewer recommendations, EPA used this poor quality study to justify the need to address “uncertain, but potentially adverse, effects.” In essence, the Agency used a poor quality study (with multiple deficiencies) in order to dismiss the recommendations of the peer reviewers.
But don’t take it from us. Steve Roberts of the University of Florida is one of the independent experts who served on the methanol peer review panel. In the latest round of feedback, Roberts states, “I think that the report represents progress in dealing with the problem of assessing risk from exogenous exposure to endogenous chemicals, but falls short of presenting a compelling case why the toxicity values are not excessively conservative.”
Kenneth McMartin of the Louisiana State University Health Sciences Center also questioned EPA’s overuse of uncertainty factors to justify the final value and stated, “In addition, the argument cited in the text for claiming a less than robust database (i.e., for justifying the UFd of 3) is not logical and can be disavowed.”
Other independent panels like the NAS have criticized EPA time and again for its reluctance to move away from default assumptions, like uncertainty factors, and embrace weight of evidence cause and effect determinations for environmentally relevant exposures.
For example, during its review of formaldehyde, an NAS panel concluded that EPA had not applied a robust weight of evidence framework in assessing whether the chemical caused a certain type of cancer. In other words, EPA failed to provide scientific evidence to support its conclusion.
As noted above, the NAS panel recommended a path forward to remedy IRIS so that it measures up to accepted scientific benchmarks. But unfortunately, EPA has not yet implemented many of the most critical recommendations, including how to deal with complicated science and exposure questions.
EPA leadership – particularly Dr. Ken Olden of the IRIS program – has made considerable progress in suggesting enhancements to the IRIS program. But EPA clearly has more work to do to improve the scientific basis of ongoing IRIS assessments.
We fully support EPA’s decision to have peer reviewers evaluate the revised draft methanol assessment. Unfortunately, the latest criticisms by the peer reviewers clearly show that fundamental deficiencies in the IRIS program remain. Moreover, the final methanol assessment highlights the deficiencies brought to light in the peer review process. An “honest broker” to help ensure assessments benefit from the input of experts outside of the Agency could be one means of assuring a better integration of the science.
Until the Agency can get the science right, the credibility and utility of the methanol assessment is questionable. As a result, the assessment could have consequences for how this valuable substance is regulated in the U.S. and, ultimately, could have a major impact on jobs and the economy.
ACC will continue to push for science-based improvements to IRIS and other government assessment programs. We look forward to working with EPA to ensure our nation’s chemical management system delivers sound public health decisions, while at the same time encouraging innovation and economic growth.
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