The downloadable data package contains information on areas in the US where air pollution levels have not met national standards. The data includes details on pollutants like ozone, lead, sulfur oxides, and particulate matter. The Environmental Protection Agency (EPA) sets standards to improve air quality, focusing on six common pollutants that can harm health and the environment. Particle pollution and ground-level ozone are the most widespread health threats. The EPA regulates these pollutants by setting limits based on human health and environmental criteria. The data is updated weekly to identify nonattainment areas across the country.