Most would agree that credible, science-based assessments of the potential risks from chemical exposures are necessary for providing both regulators and the regulated community with a useful summary of the science on certain chemicals. Very often these assessments underpin product stewardship and regulatory actions taken to protect human health and the environment.
When creating chemical assessments, U.S. Environmental Protection Agency (EPA) scientists, working in EPA’s Integrated Risk Information System (IRIS) program, gather together all of the pieces of the scientific puzzle in order to evaluate them and develop an assessment that pieces together a scientific picture that is supposed to be reflective of the facts.
Chemical assessments need to be based on the best available scientific information. In recent days, however, a campaign has been mounted by certain public interest groups to push EPA to disregard and reject relevant, high-quality scientific research from leading academics and research organizations, due to funding sources. In science, it’s the data that matters—not who funded the studies or who conducted the studies.
The Society of Toxicology, the leading professional organization of toxicologists, is crystal clear on this point, as they state in their Principles for Research Priorities in Toxicology, “[r]esearch should be judged on the basis of scientific merit, without regard for the funding source or where the studies are conducted (e.g., academia, government, or industry).”
First and foremost, then, it is scientific merit and validity that counts: study design, study conduct, data reporting, and interpretation. Independent peer review by scientific journals requires disclosure of funding sources, whether they are government grants or gifts/grants from public interest groups or the private sector, so that there is 100 percent transparency. But to the scientific peer reviewers and the journal editors, it’s the scientific work that is evaluated in determining the merits of a particular study, not the funding source or the investigator’s institution.
Studies on the risks of chemicals are frequently subject to this process of evaluation. One chemical whose level of risk has been debated over the past number of years is hexavalent chromium.
In 2008, the National Toxicology Program (NTP) published the results of a two-year animal study on the chemical’s presence in drinking water. This was the first study to find small intestinal tumors in mice—but not rats—that were exposed to the highest doses of hexavalent chromium NTP administered—doses that far exceed any naturally-occurring hexavalent chromium in drinking water.
Prior to this study, researchers had observed that the human body naturally breaks down—detoxifies—hexavalent chromium into trivalent chromium. NTP and other researchers determined that the trivalent form of chromium poses no health issues.
Unsurprisingly, researchers had a lot of questions about the NTP study: why did mice develop small intestine tumors, while rats did not? How did these tumors form? Are there early indicators that could signal the small intestine effect? Are these effects seen in other tissues?
These questions are important because they directly address the broader inquiry of the scientific community about interpreting data from animal toxicity studies and the relevance to humans. Indeed, EPA’s cancer risk assessment guidelines specify that extrapolating the results of animal testing should be based upon a sound understanding of how the chemical moves through and interacts with the human body at different levels of exposure—what scientists term ‘mode of action.’
In the wake of the 2008 NTP study, given the widespread natural occurrence of hexavalent chromium in groundwater from rocks, there was a public health imperative to more fully research this chemical’s affects, yet neither EPA nor NTP had planned to fund additional work.
It is, at this point, important to note that ACC funding does not represent mines or producers of hexavalent chromium, so there is not a direct financial gain from this research. Rather, the Council’s interest lies in doing what it can to aid chemical assessment programs, such as EPA’s IRIS program, by facilitating researchers to investigate key research questions to fill the database identified by EPA’s guidelines for producing toxicological reviews.
Developing assessments using as complete a database as possible contributes to scientifically-based chemical regulation, which benefits all parties.
The research consisted of a comprehensive series of state-of-the-art studies involving leading experts at 12 different academic and scientific institutions—all selected by an independent research firm. The research protocol was peer-reviewed prior to the study start, and the key draft manuscripts were subjected to independent peer review prior to their submission to the peer reviewed journal, where another round of peer review occurred.
Because this research builds upon the NTP study, the study director used the same research laboratory as the NTP study, under the direction of the same laboratory director, and holding as many of the NTP study conditions consistent, including the same animal chow, same animal cages, same strains of animals, same drinking water source, and same experimental doses adding two lower doses.
The peer-reviewed research on hexavalent chromium supported by ACC provides EPA and other governmental scientists with additional data, so that they may confidently assess the scientific database and set safe drinking water standards for hexavalent chromium. ACC is committed to working with EPA and other stakeholders to support a scientifically credible IRIS assessment for hexavalent chromium.
EPA has made strides to improve its IRIS assessment process. However, the June 2014 National Academy of Sciences (NAS) report makes it clear that more changes to IRIS are still needed to ensure EPA’s scientific approaches and analyses are objective. The system must begin to make full use of up-to-date scientific research—rather than continuing to rely upon default approaches to cancer risk assessments based on a 1970s understanding of the processes of carcinogenesis.
Using the full scientific database on hexavalent chromium, EPA should seize the opportunity to implement some of NAS’s suggestions on improvements surrounding mode of action. Following this approach, EPA would be capable of producing a robust IRIS assessment for hexavalent chromium—and numerous other chemicals. Yet, such results will only be achieved when EPA can piece together every part of the puzzle represented by complex research.
The science and research conducted and supported by ACC helps to provide key pieces.