Air quality monitors measure concentrations of lead throughout the country. EPA, state, tribal and local agencies use those data to ensure that lead is at levels that protect public health and the environment. EPA has tracked air quality trends for lead using data from this network of monitors. Nationally, average lead concentrations decreased dramatically after EPA's regulations reduced the lead content in on-road motor vehicle gasoline. For information on lead standards, sources, health effects, and programs to reduce lead, please see Lead Air Pollution and Vehicles and Engines pages.