Individuals who breathe polluted air can experience health effects within a few hours or days. The District measures pollutant concentrations in the local ambient (outdoor) air and uses historical data to predict pollutant levels in the future.
Air Quality Trends
The District determines the effectiveness of air quality regulations using the results of monitoring data over time. Rising pollution levels generally indicate that more controls are necessary, whereas a drop in pollution levels demonstrate that existing controls are successfully reducing emissions. This information is incorporated into air quality planning.
The District’s Air Quality Trends Report (PDF attached below) is a living document that takes a look at monitored ambient air concentrations of criteria pollutants over time as well as emissions from key sources.
Air Quality Forecasts
The District is attaining the national ambient air quality standards (NAAQS) for all pollutants except ground-level ozone. Ground-level ozone, also known as smog, is created by a chemical reaction between precursor pollutants, primarily oxides of nitrogen (NOx) and volatile organic compounds (VOCs) in the presence of sunlight and high temperatures. “Ozone season” lasts from May to September. During ozone season, air quality forecasters rate the quality of the air on a daily basis and recommend actions when predictions indicate that air quality may be bad for public health.
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