EPA Releases Draft IRIS Assessment of PFHxS and Related Salts

On July 24, 2023, EPA released a draft IRIS Toxicological Review of Perfluorohexanesulfonic Acid (PFHxS) and Related Salts.  Comments on the draft assessment will be accepted through September 22, 2023.

The IRIS assessment found that, given sufficient exposure conditions, PFHxS is likely to cause thyroid and developmental immune effects in humans.  Other evidence suggests but is insufficient to infer that PFHxS exposure might cause teratological, hepatic, neurodevelopmental, and cardiometabolic effects in humans.  EPA concluded that there is inadequate information to assess whether PFHxS exposure can result in hematopoietic, reproductive, renal, and carcinogenic effects.

PFHxS is one of three PFAS currently undergoing IRIS assessments, along with PFNA and PFDA.  EPA previously published final IRIS assessments for two other PFAS: PFBA in December 2022 and PFHxA in April 2023.

EPA Releases Draft Toxicological Review of Hexavalent Chromium

EPA recently released its draft Integrated Risk Information System (IRIS) toxicological review of hexavalent chromium (also known as chromium-6). Hexavalent chromium is used in pigment manufacturing, metal finishing and chrome plating, stainless steel production, leather tanning, and wood preservatives. It has various other industrial applications as well. The metal is also emitted into the air when fossil fuels are burned.

The metal gained significant attention in 2000 with the release of the movie Erin Brokovich. The film detailed the story of a class action lawsuit by Californians against Pacific Gas & Electric Company for dumping wastewater containing chromium into ponds, subsequently polluting groundwater supplies.

Hexavalent chromium is a known carcinogen in humans when inhaled, including increased lung cancer rates found in workers exposed at higher than normal levels in industries that process or use chromium or chromium compounds. The metal is also known to cause nasal and sinus cancers, kidney and liver damage, nasal and skin irritation, and other adverse health effects.

Less information has been known about the effects of ingesting hexavalent chromium. EPA’s current standard for the metal in drinking water is a maximum contaminant level of 100 parts per billion. The draft IRIS reports that ingestion through drinking water is likely carcinogenic, and once finalized, EPA will use the IRIS review to make assessments of risk related to ingestion exposure.

The draft is currently open for public comment until December 19, 2022. EPA Scientific Advisory Board will hold a hearing to discuss hexavalent chromium following the closing of the comment period.

National Research Council issues two reports reviewing EPA's chemical testing and science.

In the past week, the National Research Council (NRC) has released two reports on aspects of EPA’s chemical testing and science programs. Today, the NRC published a report reviewing EPA’s Integrated Risk Information System (IRIS) process for assessing chemical hazards and concluding that the agency has made substantial improvements in response to the NRC’s general recommendations made in 2011. The report published on May 2 found several key flaws in EPA’s draft “state-of-the-science” evaluation of nonmonotonic dose-response relationships for endocrine disruptors. Both reports were authored by committees of the NRC’s Board on Environmental Science and Toxicology.

The IRIS report was commissioned by Congress in response to a 2011 NRC report on EPA’s IRIS assessment of formaldehyde that found deficiencies in the agency’s general assessment methods. According to the new review, EPA is on track to make the IRIS process more effective and efficient. The agency has followed several of NRC’s 2011 recommendations; for example, EPA has implemented a new document structure that streamlines assessments, added a standard preamble explaining the process and its underlying principles, and drafted a handbook describing the process in greater detail. Noting that EPA is still in the process of making the changes recommended by the NRC, the study makes additional suggestions to strengthen to the IRIS process. Looking forward and considering the constantly evolving nature of the science involved, the report identifies critical steps to improve assessments in the future, calling for continuous updates to assessment methods, systematically identifying and addressing inefficiencies, and regular evaluation of chemical-assessment teams’ expertise and training.

The NRC took a dimmer view of EPA’s draft evaluation of nonmonotonic dose-response relationships, which intended to answer basic questions about the phenomenon wherein lower doses may be associated with larger responses, which may not be detected by traditional toxicological models. EPA’s evaluation tried to address, for example, the implications of nonmonotonic dose-response relationships for toxicity testing, weight of evidence conclusions, and risk assessment determinations. However, the authoring committee found that the process adopted by EPA in conducting the evaluation was “poorly described and inconsistent” in its approach to analyzing and summarizing data. The NRC report recommends that EPA develop and apply an “analytic plan” to predefine and document literature search strategies and establish criteria for selecting and analyzing studies, and analyze toxicity-testing strategies under more specific constraints. In addition, the NRC cited the lack of analysis supporting EPA’s conclusion that nonmonotonic dose-response relationships can have both qualitative and quantitative effects which would be considered appropriately using current risk-assessment practices. The report urges EPA to address how nonmonotonic dose-response relationships for estrogen, androgen, and thyroid pathways would be treated under current risk-assessment practices. Although the report does not address more fundamental questions – such as whether endocrine-disrupting chemicals are harmful, or the adequacy of EPA’s testing techniques – the NRC’s critique may raise issues in other areas, including the U.S.’ trade in chemicals with the European Union, which has adopted a more aggressive approach to regulating potential endocrine disruptors.

EPA Draft (IRIS) Ammonia Assessment Available for Public Comment

Integrated Risk Information System (IRIS):

Today, EPA released for a 60-day public comment period the draft IRIS assessment for ammonia.   Excerpts from the agency’s press release are provided below, and a copy of the draft assessment is avaialble here

IRIS is a human health assessment program that evaluates information on health effects that may result from exposure to environmental contaminants. Through the IRIS Program, EPA attempts to provide the highest quality science-based human health assessments to support the Agency’s regulatory activities.  The IRIS database is web-accessible and contains information on more than 550 chemical substances.  Readers familiar with IRIS will recall the various criticisms of the agency’s evaluation process, which EPA has been attempting to address, as described in further detail here.  General background information on IRIS is available here.



June 1, 2012 

EPA Draft Ammonia Assessment Available for Public Comment

Draft assessment continues agency’s responsiveness to NAS recommendations 

WASHINGTON – The U.S Environmental Protection Agency today announced the release of its draft Integrated Risk Information System (IRIS) health assessment for ammonia. The draft assessment will be available for public comment for 60 days and will be sent for independent expert peer review.

Ammonia is used in agricultural fertilizers, the manufacture of pharmaceuticals and explosives, water purification, household cleaners, as a refrigerant, and in many industries. Scientific studies show that ammonia can affect the respiratory system. The draft assessment includes an estimate of the amount of ammonia a person can inhale daily throughout a lifetime that is not likely to cause harmful health effects, which is less stringent than the current value for ammonia on IRIS.

 The draft IRIS assessment for ammonia represents major progress for EPA in implementing the April 2011 National Academy of Sciences (NAS) recommendations for improving IRIS assessments. The draft assessment uses a new streamlined document structure that is more transparent and clear; includes a template for describing the literature search approach; identifies the strengths and weaknesses of analyzed studies; and describes how EPA applied their guidance, methods, and criteria in developing the assessment.

 When the assessment is final it will be posted to the IRIS database. IRIS is a publicly available online database that provides high quality science-based human health assessments used to inform the agency’s decisions on protecting public health and the environment.

  The IRIS database contains crucial information on more than 550 chemical substances and their impacts on human health. Governments and private entities use data from IRIS in conjunction with exposure information to help characterize the public health risks of chemical substances. These characterizations are then considered in risk management decisions to protect public health.