What is pollution? According to Peter H. Aranson, “Public policy regards as pollution any man-made or naturally occurring substance (for example, smoke or sewage) or condition (for exam- ple, noise, heat, or radiation) that is believed to threaten human health or economic welfare...

Can we know the risks we face, now or in the future? No, we can¬ but yes, we must act as if we do. Some dangers are unknown; others are known, but not by us because no one person can know everything. Most people cannot be aware of most dangers at most times. Hence, no one can calculate...