Industry was the only source of data on these matters and industry was under no obligation to tell what it knew. Studies that are not published in the open literature cannot be criticized. Their methods and reasoning cannot be scrutinized. In short they cannot participate in the scientific process that leads to consensus. In 1972, a Dupont industrial hygienist joined the committee.
Workers are different from the general public.
Most of them are white, most of them are males. There are no babies in the workplace, no old people, no chronically ill people. Standards intended to protect only workers will definitely not adequately protect the general public. The next time someone tells you their project is going to meet all state and federal standards, look into it very closely. You may be unpleasantly surprised.