A tightly-contested midterm race could see a biochemist unseat a GOP incumbent backed by a trade group for the chemical industry, in part due to a recent scandal over dangerous chemical emissions.

Illinois’s sixth district House seat is currently held by Republican Peter Roskam, who’s held the seat since 2007. But Democratic candidate Sean Casten, a political newcomer and former biochemist who ran clean energy companies, is giving the incumbent a run for his money in a race that recent polls show is still quite close.

One of the biggest issues in the race is the environment and while Roskam’s campaign frequently calls him a friend to the environment, his voting record in Congress and support from the chemical industry have called this position into question.

This became further exacerbated towards the end of August when the Department of Health and Human Services released a report about high levels of Ethylene Oxide (EtO)—a toxic gas that can increase the risk of certain cancers—being emitted from a medical equipment sterilization company in the district. While other local politicians were calling for the plant, owned by a company called Sterigenics, to be shut down, Roskam said nothing for two weeks, and has remained reserved on the issue.

Using air modeling data provided by the Environmental Protection Agency, HHS determined that there was a high concentration of EtO in the air around Sterigenics, including nearby homes and schools. It found that due to these levels of EtO, people in the area were at a higher risk of developing cancer, with some areas having rates as high as nine times the national average.

“These elevated risks present a public health hazard to these populations,” the report read.

Casten held a press conference saying he was “extremely concerned” about the report and pointed to the current administration’s anti-science rhetoric as creating the backdrop that allows these kinds of problems to persist. He also criticized Roskam for not commenting on the issue, which he did in a statement two weeks after the report was published, though he did not immediately call for the shutdown of Sterigenics.

Casten’s campaign has pointed to Roskam’s backing from the American Chemistry Council—an industry trade association for US chemical companies, a large portion of which are located in Illinois—as an explanation for his lack of response to the Sterigenics scandal. Along with the ACC spending a reported $209,000 on advertisements supporting Roskam, Roskam has a record of siding with the ACC when voting on issues in Congress that the organization has lobbied on—such as an act that would have allowed private industry stakeholders to serve on the EPA’s scientific advisory council (the bill was passed by the House but lost steam in the Senate.)

Veronica Vera, a spokesperson for Roskam’s campaign, told me he has called for Sterigenics to temporarily shut down (Motherboard could not find a public statement from Roskam calling for the shut down), and said that while he wasn’t publicly talking about the issue at first, he had been working to get to the bottom of it from the day the report was released.

“Within a week of the first report, Roskam’s office initiated communication with Willowbrook Mayor Frank Trilla to get a better understanding of the situation,” Vera wrote in an email. “Over the course of next couple of weeks, Roskam spoke several times with the Illinois EPA and U.S. EPA Region 5 Administrator, Cathy Stepp, to get the answers the affected communities were seeking.”

Vera also highlighted times when Roskam has taken a pro-environment stand during his time in Congress, such as when he opposed President Trump’s FY18 budget proposal that eliminated the Great Lakes Restoration Initiative, and when he secured funding for an environmental cleanup project in his district.

But the questions surrounding Roskam’s support from the chemical industry raised by Casten’s campaign seems to have worked in the Democrats favor, in light of the Sterigenics scandal. In recent weeks, Casten has inched ahead in the polls and is now leading the incumbent.