The new engine standards will provide substantial, long-term improvements in the nation's air quality and public health and help the nation meet the EPA's new air quality standards for smog and fine particles. The reduction is equivalent to taking six million heavy trucks off the road. New cost-effective standards will be a major step forward in reducing threats to public health and the environment from smog and particulate matter. Nitrogen oxides from diesel engines are a major contributor to the formation of ground-level ozone and particulate matter.
Ozone reduces lung function and aggravates existing respiratory problems such as asthma.
It can also cause a breakdown in a person's ability to fight off infectious bacteria. Particulates become lodged in the lungs' most sensitive tissue and may result in premature death. In addition, ozone, particulate matter and nitrogen oxides cause crop damage, acid rain, and reduction in visibility. In the first rule, EPA finalized a new, combined nitrogen oxides and hydrocarbon emission standard for heavy duty diesel engines used in trucks and buses that becomes effective with the 2004 model year. The nitrogen oxides reductions also will reduce nitrate particulate matter and acid rain.