Usually, we do not even study the exposed individuals in any systematic way. Wildlife may or may not be studied. In the case of humans, we almost invariably wait until they notice symptoms in themselves. Then we generally ignore them until they become desperately angry and get themselves organized into a political force. It is not a philosophy based on prevention.
Victims have to prove harm before controls can be initiated.
Although corporate polluters complain bitterly that they are being strangled by environmental regulations, in truth, all of the nation's environmental laws, taken together, impose controls on only about 350 individual chemicals. There are 71,000 chemicals in commercial use today, so our regulatory system imposes controls on one-half of one percent of the chemicals currently in use. We learn after the fact that we have begun to heat up the planet by our emission of greenhouse gases. We learn after the fact that our refrigerators and air conditioners have eaten holes as big as the United States in the atmosphere over the north and south poles. We watch cancer rates steadily rise and after about three decades of this, we begin to scratch our heads.