Air pollution, waste incineration, the accident at the AZF plant in Toulouse: what are the health risks? How can we assess, monitor, and evaluate policies designed to reduce them? This is the focus of the health monitoring approach, which utilizes two interrelated and complementary tools: epidemiology and risk assessment. For while the risk associated with environmental exposure is, in most cases, low, the impact can be considerable due to the number of people exposed to the threat.