Cheap solar cells and panels from overseas will now be subject to a 30 percent tariff, the Trump administration announced on Monday. The decision is aimed at boosting the competitiveness of US-made solar panels. But opponents say that the tariffs could drive increases in pollution and endanger jobs in America’s $29 billion solar industry.

The announcement comes after the International Trade Commission’s ruling in September that the companies SolarWorld AG and Suniva couldn’t compete with cheap solar panel imports. Both companies manufacture panels in the United States but are in fact foreign-owned, Bloomberg reports: SolarWorld AG is the American arm of a German company, and Suniva has a Chinese majority owner.

The solar industry employs more than 370,000 people in the US — more than twice as many as coal, according to the Department of Energy’s 2017 employment report. Suniva argues that stiffer tariffs would add yet more manufacturing jobs. But Reuters reports that manufacturing accounts for just 14 percent of jobs in the solar sector. Most of the jobs are actually in installation, which could see demand dwindle as panel prices rise.

The 30 percent tariff will last four years, dropping to 15 percent over that time period, The New York Times says. Not everything will be taxed, either: “the first 2.5 gigawatts of imported solar cells will be exempted,” the Times reports. Still, even the threat of tariffs has already prompted solar developers to stop construction and start hoarding solar panels, Bloomberg reported in September. The Solar Energy Industries Association, a US trade group, came down hard on the tariffs announced today. “They will create a crisis in a part of our economy that has been thriving, which will ultimately cost tens of thousands of hard-working, blue-collar Americans their jobs,” Abigail Ross Hopper, SEIA’s President and CEO, said in a statement.

Beyond harming job growth, the tariffs could also hinder efforts to make the US power grid cleaner and more renewable, environmental advocacy groups say. “If Trump really wants to put America first, he should reduce our reliance on polluting energy sources that fuel climate change,” Howard Crystal, senior attorney with the Center for Biological Diversity, said in a statement. “Instead, this profoundly political move will make solar power more expensive for everyday Americans while propping up two failing, foreign-owned companies.”