Ozone Days By County

Air pollution is a deeply underappreciated risk to health. More than half of the U.S. population lives in areas where either the ozone or particle pollution—or both—is often dangerous to breathe.

Ozone is the primary ingredient of smog. Unlike the beneficial ozone layer in the upper atmosphere that shields the sun’s ultraviolet radiation, ground-level ozone attacks lung tissue by reacting chemically with it. Ozone is formed when nitrogen oxides (NOx) and volatile organic compounds (VOCs) come in contact with heat and sunlight. NOx are emitted by power plans, motor vehicles and other sources of high-heat combustion. VOCs sources include motor vehicles, chemical plants and factories.

However, ozone exposure, even at levels deemed safe by current air standards, can negatively affect lung function. There is direct correlation between higher ozone-level exposure and decrease in lung function. Ozone pollution can shorten life.

Ozone is a significant problem in Dallas-Fort Worth, with all counties experiencing at least 50 percent more unhealthy air quality days than the rest of Texas. Tarrant County leads the four counties with 39 annual unhealthy days, followed by 32 for Denton, 29 for Dallas and 28 for Collin counties.