January 2018 emails between the EPA, the White House, and the Department of Health and Human Services (DHHS) made public following a Freedom of Information Act request showed that the White House and EPA under Pruitt decided to halt the publication of a study done by the DHHS Agency for Toxic Substances and Disease Registry (ATSDR). The study, an assessment of the chemical pollutants PFOS and PFOA, showed that the substances present dangers to human health at far lower levels than the EPA previously deemed safe. An email from a White House official said that the administration feared a "potential public relations nightmare."