Ozone pollution causes the risk of developing respiratory diseases to grow. The risk is 40% to 50% higher in heavily polluted areas such as very big cities and is 35% higher throughout the rest of the country. 

 

Ozone is one of the most widespread pollutants, one of the greenhouse gases that cause the global warming process and one of the main components of smog, which has high levels in densely-populated urban areas. 

 

Several studies on ozone concentration and its effects have been carried out until now, but this study is like no other study on ozone carried out before because, unlike the others, it spans over 18 years thus analyzing the effects on a long term. 

 

The study analyzed as many as half a million people in 96 metropolitan areas, the New England Journal of Medicine wrote, and is the first showing that people who are exposed to low levels of ozone are also in danger. Not only high levels of ozone are deadly. Ozone is deadly. 

 

The ground-level ozone has very different effects than the ozone layer above the Earth which protects from ultraviolet radiation, said Michael Jerrett, professor of environmental health sciences at the University of California-Berkeley and lead author of the study. 

 

The cities with the highest ozone concentration are Riverside, San Bernardino and Ontario, Calif., while cities like San Francisco and Portland have the lowest level. 

 

The number of Americans who die of respiratory diseases is of 240,000 per year. 

 

The Environmental Protection Agency may need to review the current safety standards for ozone. 

 

For a list of the ozone concentration in the major U.S. cities visit this link.