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Climate Change is a Threat to Health: More Heat, More Ozone

High in the Earth's atmosphere, naturally occurring ozone is essential to protecting life on Earth from the harmful ultraviolet rays of the sun. However, here on Earth's surface, ground-level ozone is a harmful pollutant. 

Source of Ozone: Ground-level ozone is formed when two major classes of air pollutants -- nitrogen oxides and volatile organic compounds (VOCs) -- combine with oxygen in the presence of sunlight. VOCs are emitted naturally by plant life, and also by human industrial activity:  from coal combustion in power plants,  from chemical plants, gasoline, oil-based paints, and auto body and print shops. Nitrogen oxides result primarily from fossil fuel combustion in power plants, industrial furnaces and boilers, and motor vehicles. 

Ozone and Climate Change: Scientists have found that higher temperatures accelerate the reaction between nitrogen oxides and VOCs, creating more ozone. By 2050, climate change alone is projected to increase summertime ozone concentrations by 2 to 8 parts per billion from today's concentrations. 

Health Impacts: Ground-level ozone is associated with many respiratory and cardiovascular ailments and is harmful even to healthy people. Breathing in high ozone levels causes an effect that has been likened to "sunburn of the lungs." It can create difficulty breathing, aggravation of asthma, development of new cases of asthma, emphysema, chronic bronchitis, and pneumonia.

Ozone can also affect the heart, leading to cardiac arrhythmia and heart attacks. It can also increase the number of low birth-weight babies in mothers exposed to high levels during pregnancy. 

Health-related costs of climate change effects on ozone air pollution have been estimated at $6.5 billion annually, nationwide. 

Ozone can also impact human health by inhibiting photosynthesis and plant growth, thus reducing yields from food crops. 

Health Advice for Bad Air Days: The U.S. Environmental Protection Agency uses an air quality index to rank the day's ozone levels from good to very unhealthy.  Levels are highest on hot, sunny days and are exacerbated by traffic and nearby industry. People with lung disease, including asthma, children, and the elderly are advised to limit outdoor activity when levels reach a ranking over 100.