On Wednesday, Senate lawmakers will weigh whether to confirm as the chemical industry’s top regulator a scientist who over the past two decades has helped companies argue against stricter government regulation of potentially harmful compounds in everyday products.

Critics say Michael Dourson, a University of Cincinnati professor and longtime toxicologist, is too closely tied to the chemical industry, and has too many conflicts of interest, to be considered for such a post. They point specifically to the nonprofit consulting group he founded in 1995, which over the years has produced research for chemical companies that showed little or no human health risks for their products.

If Dourson, who worked at the EPA from 1980 through 1994, is confirmed to head the agency’s Office of Chemical Safety and Pollution Prevention, he potentially could oversee the review of chemicals produced by companies that he has represented in the past.

“In my view, EPA needs someone who at least will entertain the notion that it has not been protective enough [in safeguarding against risks],” said Adam Finkel, an environmental law expert who once worked on a project with Dourson. “His views are the opposite, and I think they are ill-informed.”

The Environmental Defense Fund, an advocacy group, has described Dourson as a “hired gun” for the chemical industry who has “made a career downplaying concerns about chemicals, from harmful pesticides to cancer-causing solvents, paid for that work by the same companies that make or use those chemicals.”

Dourson could not be reached for comment. But the EPA has stood firmly behind his nomination, touting his experience with the agency and his hefty track record of research. In announcing his selection this summer, the agency included recommendation letters from an array of outside supporters, including the director of a Christian family camp in Michigan and a University of Minnesota professor who called Dourson a “wealthy resource of scientific information.”

Some industry representatives also have embraced his nomination. CropLife America, which represents pesticide companies, called Dourson “a perfect fit” for the job. A long list of other organizations, from the American Chemistry Council to Plastics Industry Association, recently urged lawmakers to confirm Dourson and a handful of other EPA nominees.

Dourson is not the only EPA nominee likely to face some opposition this week. A Senate committee on Wednesday also will consider the nomination of Bill Wehrum to head the agency’s Air and Radiation Office. Wehrum spent years at the EPA during the George W. Bush administration and became the acting head of the air office in 2005. President Bush nominated him to lead the office in 2006 but eventually withdrew the nomination after it became clear the Senate did not intend to confirm him.

Wehrum, an expert in Clean Air Act issues, currently is a partner the law firm of Hunton & Williams, where he has represented a variety of oil, gas, coal and chemical companies.

“Bill is committed to the Clean Air Act and to the rule of law,” Jeff Holmstead, the head of the EPA’s air and radiation office in the mid-2000s, wrote in a recent letter to lawmakers. “He is also a person of the highest integrity.”

But Wehrum is almost certain to face opposition from Senate Democrats over his industry ties.

“I don’t think his record of weakening air pollution standards and deferring to industry on public health protections makes his nomination any more acceptable in 2017 [than in 2006],” said Sen Thomas R. Carper (Del.), the ranking Democrat on the Senate Environment and Public Works Committee.