WASHINGTON, D.C. — According to the Boston-based Clean Air Task Force an estimated 20,000 Americans a year to die sooner than they would have otherwise, due to emissions from old diesel engines, reports The Los Angeles Times. Diesel pollution is blamed for contributing to asthma, respiratory diseases and heart attacks. The study estimates the risk of health complications from diesel exhaust for people living in cities is three times higher than the risk for those in rural areas. According to the task force study, the metropolitan areas with the highest number of early deaths from diesel engines were New York, Los Angeles, and Chicago, although the study also included the surrounding suburbs; so New York's estimated total of 2,729 deaths included parts of New Jersey and Connecticut. The group said it based its figures on the most recent government emissions data – from 1999 – and from public health studies of the effects of various types of air pollutants. In response, Allen Schaeffer, executive director of the Diesel Technology Forum criticized the report's assumptions and conclusions, saying, "I think they have overstated the risk here using data that's 6 years old." The Environmental Protection Agency last year required new diesel engines on trucks and buses to cut in half the amount of nitrogen oxides produced. In 2007, emissions are to be cut further. However, Conrad Schneider, co-author of the report and advocacy director for the Clean Air Task Force, pointed out that regulations designed to make new diesel engines cleaner didn't affect millions of older trucks, buses and construction engines. "Those are great rules; they will hold new engines to higher standards. In the meantime, we're stuck with a legacy of dirty diesel engines," said Schneider.