Let's not forget the many billions already wasted on Superfund, asbestos removal, and radon protection. But costs go up exponentially as one tries to remove the last bit of pollution. A completely clean environment would consume an unacceptable fraction of household income and lead to a lower standard of living, poorer housing and medical care. When the cost becomes too high, people will no longer support tighter standards with ever-increasing expenditures to remove pollutants. The problem though is that the costs are often hidden so that an informed choice is not available.
Cost is the main reason why so much of the developing world is still heavily polluted.
When it's a choice between food or clean air, food will win. Once a certain standard of living has been achieved, people demand a cleaner environment and are willing to pay for it. But it also looks at the natural pollution levels that are outside of human control. For example, with the existing background of cosmic rays and other natural radioactivity, there is little point in demanding that exposure to manmade radiation be reduced to zero. A similar argument holds for air and water pollution.