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ACC’s Hexavalent Chromium Panel: EPA’s Draft IRIS Assessment Is Not Based on the Best Available Science and Is Inconsistent with Respected International Authorities

Allison Edwards

WASHINGTON (December 20, 2022) — Today, the American Chemistry Council’s (ACC) Hexavalent Chromium Panel submitted comments to the Environmental Protection Agency (EPA) on its 2022 Draft IRIS Toxicological Review of hexavalent chromium and issued the following statement:

“The weight of the evidence supports that hexavalent chromium operates by a non-mutagenic, threshold mode of action. Instead, EPA used a cancer slope factor that has the potential to lead to an extremely low maximum contaminant level (MCL).

“The current draft assessment does not use the best available science and is at odds with the findings of over 30 peer-reviewed scientific publications supporting a non-mutagenic, threshold mode of action. These peer-reviewed studies provide support that the current EPA drinking water standard for total chromium of 100 parts per billion is health protective.

“The draft assessment’s approach and results could lead to a tap water value that is nearly 3,000 times lower than EPA’s current drinking water standard (or MCL) and is orders of magnitude below the average groundwater concentration of hexavalent chromium in the United States. Extensive data indicate that adverse health effects do not occur at the current EPA drinking water standard and it is protective of human health.

“Importantly, EPA’s draft assessment is not consistent with other regulatory and scientific authorities, including Health Canada, the World Health Organization, and the Food Safety Commission of Japan, who have reviewed the available data and concluded that threshold-based safety criteria are protective against both cancer and non-cancer health effects of hexavalent chromium. EPA must address why this assessment is so far out of touch with the work of these other international authorities.

“EPA’s draft assessment minimizes the importance of the most recent high-quality research and any future regulatory action could have little to no measurable public health benefit. We look forward to engaging with the EPA Science Advisory Board panel when it evaluates the draft assessment early next year.”


National and international regulatory agencies have set drinking water standards to protect the public from all forms of chromium in drinking water. EPA has set a drinking water standard of 100 ppb for total chromium. This includes all forms of chromium, such as hexavalent chromium and trivalent chromium, and the EPA standard assumes 100 percent hexavalent chromium.

Over 30 peer-reviewed studies supporting a non-mutagenic, threshold mode of action show that there was no observed toxicity in rodents exposed to hexavalent chromium concentrations in drinking water at the current total chromium MCL. In fact, at hexavalent chromium concentrations of 1,400 ppb – more than 10 times the current drinking water standard for total chromium there was no observed toxicity in rodents. Researchers did not observe toxicity in the rodents until the hexavalent chromium dose was 5,000 ppb – 50 times the total chromium drinking water standard. Thus, drinking water containing 100 ppb or less total chromium would not be expected to cause intestinal hyperplasia, a precursor to the development of cancer, in humans. The research has undergone robust review, including review by an independent third-party Science Advisory Board, multiple rounds of peer review, and the research findings and all data have been made publicly available at https://cr6study.info/.

American Chemistry Council

The American Chemistry Council’s mission is to advocate for the people, policy, and products of chemistry that make the United States the global leader in innovation and manufacturing. To achieve this, we: Champion science-based policy solutions across all levels of government; Drive continuous performance improvement to protect employees and communities through Responsible Care®; Foster the development of sustainability practices throughout ACC member companies; and Communicate authentically with communities about challenges and solutions for a safer, healthier and more sustainable way of life. Our vision is a world made better by chemistry, where people live happier, healthier, and more prosperous lives, safely and sustainably—for generations to come.

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