The role of weather and other natural factors in air pollution remains a fact of life. Weather can exacerbate air pollution problems. The tragedy in Donora involved an unusual meteorological episode, but what made it deadly was the human-caused pollution in the air. Our knowledge about these kinds of interactions has evolved over the years, and so have our policies and standards. The history of how states and EPA have worked together to develop programs to address ground-level ozone is an excellent example of how EPA's approaches factor in unusual climatic episodes in developing plans to reduce emissions.
Ozone is unhealthy to breathe, even at low levels.
It affects a variety of individuals, including healthy children and adults who are active outdoors during the summer. Ozone can also aggravate asthma, and make people more sensitive to allergens. Ozone also increases people's susceptibility to respiratory infections. It can inflame and damage the lining of the lungs, much like a sunburn. Unlike many other pollutants, ozone is not emitted directly into the air.