At the beginning of the year, the Agency for Toxic Substances and Disease Registry (ATSDR) prepared to release a study that shows that toxic chemicals are contaminating water supplies across the nation—and since January, the Environmental Protection Agency (EPA) and the White House have blocked publication of it for political reasons, as revealed by newly disclosed emails.

Per Politico:

“The public, media and Congressional reaction to these numbers is going to be huge,” one unidentified White House aide said in an email forwarded on January 30 by James Herz, a political appointee who oversees environmental issues at the OMB. The email added: “The impact to EPA and [the Defense Department] is going to be extremely painful. We [DoD and EPA] cannot seem to get ATSDR to realize the potential public relations nightmare this is going to be.”

The emails were released to the Union of Concerned Scientists via a Freedom of Information Act request. A lobbyist with the group, Yogin Kothari, told Politico that an email sent by Nancy Beck, deputy assistant administrator for EPA’s Office of Chemical Safety and Pollution Prevention, is extremely troubling because it appears as though the White House is trying to interfere in a science-based risk assessment.”

Former EPA official Judith Enck noted that the emails include “no mention of the people who are exposed to PFOA or PFOS, there’s no health concern expressed here.”

In 2016, the EPA released a voluntary health advisory about PFOA and PFOS, fluorinated organic chemicals that are part of a larger group of chemicals called perfluoroalkyl substances (PFASs). They are often found in public drinking water sources. The advisory said that exposure at levels around 70 parts per trillion could be dangerous; that risk was calculated based on the drinking water intake of lactating women, who can pass these chemicals to nursing babies. Per Politico, “One part per trillion is roughly the equivalent of a single grain of sand in an Olympic-sized swimming pool.”

This new study shows that the chemicals actually endanger health for the control group of breastfeeding mothers at a far lower level: less than one sixth of what was previously called safe by the EPA. Per the agency, exposure can have the following health impact:

Studies indicate that exposure to PFOA and PFOS over certain levels may result in adverse health effects, including developmental effects to fetuses during pregnancy or to breastfed infants (e.g., low birth weight, accelerated puberty, skeletal variations), cancer (e.g., testicular, kidney), liver effects (e.g., tissue damage), immune effects (e.g., antibody production and immunity), thyroid effects and other effects (e.g., cholesterol changes).

“Families who have been exposed to emerging contaminants in their drinking water have a right to know about any health impacts, and keeping such information from the public threatens the safety, health and vitality of communities across our country,” Senator Maggie Hassan (D-N.H.) said in a May 14 letter to the EPA and Department of Health and Human Services (HHS) demanding the release of the study.

According to Politico, “contamination is so widespread, the chemicals are found in nearly every water supply that gets tested.” The unreleased study could substantially increase cleanup costs for military bases, chemical manufacturing plants and neighboring communities, which would be required to treat their drinking water supplies if government agencies did not. Studies show that a disproportionate number of people of color live near chemical manufacturing plants in the United States.

While the EPA sought to avoid what it called a “public relations nightmare,” residents of one of America’s cities most affected by contaminated water were informed by government officials that their water was safe. In April, Michigan Governor Rick Snyder announced that the state would no longer provide free bottled water to residents of majority-Black town Flint, who are four years into an ongoing water crisis. “We have worked diligently to restore the water quality and the scientific data now proves the water system is stable and the need for bottled water has ended,” Snyder said.

HHS confirmed to Politico that the study currently does not have a scheduled release date.