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ACC’s Hexavalent Chromium Panel Comments on EPA’s Draft IRIS Assessment

The Draft IRIS Assessment Does Not Use the Best Available Peer-Reviewed Science

Allison Edwards

WASHINGTON (October 20, 2022) — Today, the American Chemistry Council’s (ACC) Hexavalent Chromium Panel issued the following statement on the release of the Environmental Protection Agency’s (EPA) 2022 Draft IRIS Toxicological Review of Hexavalent Chromium:

Hexavalent Chromium Panel, American Chemistry Council (ACC)
We are reviewing the details of the draft IRIS assessment and have strong concerns that the conclusions of the latest state-of-the-art research on hexavalent chromium have been ignored.

“EPA currently has in place a maximum contaminant level (MCL) of 100 parts per billion (ppb) total chromium based on the assumption of 100 percent hexavalent chromium in the water. Results from a series of state of the art, peer-reviewed studies provide support that the current EPA drinking water standard is health protective. 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/.

“These studies 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 ten 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.

“Furthermore, this research has been validated by other regulatory bodies, including Health Canada, the World Health Organization, and the Food Safety Commission of Japan, each of which concluded that the weight-of-evidence supports a non-mutagenic, threshold mode of action for intestinal tumors.

The draft IRIS assessment is at odds with the findings of over 30 peer-reviewed studies supporting a non-mutagenic, threshold mode of action, and we will be engaging with EPA to understand why its assessment is not consistent with the best available science.”

  • 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 parts per billion (ppb) for total chromium. This includes all forms of chromium, and the EPA standard assumes 100 percent hexavalent chromium.
  • In 2020 the World Health Organization issued a final background document that recommends retaining the current WHO guideline value for total chromium (50 ppb) based on “the newer, high-quality data from chronic drinking water carcinogenicity studies” noting that the “overall weight-of-evidence supports a threshold MOA.”
  • In 2019 the Food Safety Commission of Japan published a risk assessment of Cr(VI) in drinking water, concluding genotoxic mechanisms were unlikely to contribute to the tumors in rodents, and finding a threshold can be established.
  • In 2018, Health Canada issued a final maximum acceptable concentration of 50 ppb for total chromium, finding the weight of evidence, including review of the large body of peer-reviewed published MOA studies, supports a non-mutagenic, threshold MOA for intestinal tumors.
  • In 2016, the Texas Commission on Environmental Quality published its final support document setting a reference dose of 0.003 mg/kg/day (about 100 ppb) for hexavalent chromium to be protective of both cancer and non-cancer effects. This hexavalent chromium reference dose is identical to that used by EPA in developing the current MCL for total chromium of 100 ppb.  
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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