The environmental chiefs from two past Republican administrations endorsed Democratic presidential nominee Hillary Clinton on Tuesday, saying GOP nominee Donald Trump is too ignorant for them to support.

“Donald Trump has shown a profound ignorance of science and of the public health issues embodied in our environmental laws,” the former heads of the Environmental Protection Agency said in a letter sent to Clinton. “He hasn’t a clue about Republicans’ historic contributions to science-driven environmental policy: the incontestable environmental improvements in the restored lakes and rivers, the acid rain controls, the reduction of key air pollutants by 70, 80 and 90 percent, and the sharp decline in pollution from automobiles even as their numbers more than doubled.”