David Dunlap, a deputy in the Environmental Protection Agency’s Office of Research and Development, has played a lead role in crafting the EPA’s policies on several toxic chemicals found in drinking water, raising concerns about conflicts of interest due to his previous work at Koch Industries.

Politico on Monday first reported that Dunlap has helped spearhead the EPA’s policies on a class of chemicals linked to cancer: perfluoroalkyl and polyfluoroalkyl substances, or PFAS. Dunlap was hired in October after working for the chemical giant Koch Industries for more than eight years as a lead expert on water and chemical regulations.

Dunlap attended at least nine meetings on the substances during his first six weeks at the agency, according to copies of his calendars obtained by Politico through a Freedom of Information Act request. At the same time, acting EPA Administrator Andrew Wheeler was deciding if the agency would choose to regulate some of the most notable chemicals in the PFAS class.

Politico reported last week that Wheeler ultimately decided not to set a limit for two of the toxic chemicals that have been found in drinking water ― perfluorooctanesulfonic acid, or PFOS, and another called perfluorooctanoic acid, or PFOA. The decision has not yet been made public, but the calendars show Dunlap was involved in the decision-making process shortly after he started at the agency.

A bipartisan group of 20 senators issued a forceful letter urging Wheeler to reconsider this week, saying a failure to regulate the substances “would be a major setback to states and affected communities.”