What Makes Outdoor Air Unhealthy

Ozone (also called smog) is currently one of the least-well-controlled pollutants in the United States. It is also one of the most dangerous—and it's invisible.

Particulate matter (also called particle pollution or soot) refers to a mix of very tiny solid and liquid particles that are in the air we breathe. It is dangerous enough to shorten your life.

Nitrogen dioxide is a gas that comes from burning fuels. Live near a busy highway or a power plant that burns gas? You may be breathing a lot of nitrogen dioxide.

Sulfur dioxide forms when sulfur-containing fuel such as coal, oil or diesel is burned. Live near a power plant or a port? You may have more sulfur dioxide in your air.

Nearly 200 other pollutants emitted into the air can cause diseases, including lung cancer, or cause other harmful effects.

Power plants that burn coal, gas, oil and biomass produce harmful air pollutants. Generating electricity from zero-emission sources instead, like solar and wind, is critical for lung health.

All vehicles that burn fuel, like gas and diesel, pollute the air and harm human health - cars, trucks, planes, ships, trains, and more. Pipelines that transport fuels add to air pollution, too. Switching to zero-emission transportation is essential for healthy lungs.

Heating, cooling and powering our homes all produce emissions that can harm health, including in our own neighborhoods.

This infographic has more information on how methane gas (also called "natural gas") specifically harms health at every stage of its journey.

Harmful emissions come from heating, cooling and powering businesses and industrial operations, as well as from manufacturing processes.

Wildfires, flooding, hurricanes and other natural events can create unhealthy air, especially for people with lung disease. And the cleanup often adds to the challenge.

Climate change poses a grave health threat to everyone, with serious risks to lung health.