Almost everyone agrees on the importance of keeping our air and water pollution-free. But how much are we willing to pay and for what measure of protection? The Environmental Protection Agency (EPA) has been criticized for setting clean air standards without regard for the costs of meeting those standards. Critics of this approach argue that failing to weigh costs and benefits could threaten economic growth, which has its own implications for public health. How should the EPA set its standards? Can cost-benefit analysis lead to standards that are both efficient and effective?