I've never seen any environmental measure change four-fold over 10 years. The decline reflects the drop in exposure to second-hand smoke through indoor smoking bans and decreased smoking overall. Elevated blood lead is considered to be 10 micrograms or higher. CDC officials said that detecting chemicals such as plastic derivatives in most people is not, of itself, cause for alarm. This was echoed by David Ropeik, an official at the Center for Risk Analysis at the Harvard School of Public Health.
Exposure is part of the definition of risk.
The problem is, if our fears don't match the actual risks, we start to demand protection from risks that don't exist.