WASHINGTON (CN) - The Environmental Protection Agency will add a new safety threshold for exposure to nitrogen dioxide to 100 parts per billion maximum per hour at all air quality testing sites around the country.
The additional standard is expected to significantly alleviate respiratory distress in high risk populations by limiting their maximum exposure, at any given time, to nitrogen dioxide.
The threshold will be applied to each testing site based on a three year average of the one hour maximum nitrogen dioxide concentrations at the site. This new standard is in addition to a total annual average exposure (all hourly exposure concentrations average over one year) of 58 parts per billion.
Exposure to high concentrations of nitrogen dioxide has been linked with respiratory distress caused by inflammation of the lungs. This effect is more common in the very young, the elderly and people with preexisting respiratory problems.
Nitrogen dioxide is primarily produced by internal combustion engines and thermal power stations.
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