Currently, national ozone standards are set at 75 parts per billion, but the EPA is thinking of further lowering the level to somewhere in the 60-70 ppb range because of the impacts ozone pollution can have on the environment and human health. In a study conducted at Rice University in Houston, eight years worth of data was analyzed, and results proved a positive correlation between people experiencing cardiac arrest and exposure to ozone and fine particulate matter. Researchers concluded that with an average increase of 6 micrograms in particulate matter over the course of two days, the risk for cardiac arrest, especially among those with a pre-existing condition, raised by 4.6%.
http://www.sciencedaily.com/releases/2013/02/130217134200.htm
