No dispute here. The controversy rises over whether or not this level damages human biology. A little history explains why the government agencies and chemical industry insist the level poses no threat. The 19th century chemical industry developed methods of assessing dangers of chemicals in the workplace. A factory is enclosed, relatively small.
Workers come in contact with a small number of chemicals, easily tracked.
Factory dangers are easy to check. When U.S. EPA and Environment Canada were created in the early 1970s, these agencies thought of the environment as one big workplace. Epidemiology tries to link a chemical exposure to some observed ill. Such a study might ask, for instance, if the level of organochlorines in your food causes declining sperm count. You may or may not find the criminal, but failure doesn't mean no criminal exists.