Cohan and Rice alumna Ran Chen also documented that air pollution continued to decline even after the 2009 standards were met. The majority of the SIP regions had already attained the mandated 2014 goal of 12 micrograms per cubic meter by 2012.
"We've been on a good trajectory," Cohan said. "This demonstrates that the combination of state and federal controls has been substantially improving air quality in the U.S."
Recent stories about the ongoing crisis in Beijing, where PM has reached hazardous levels, and in rapidly industrializing countries such as India set the U.S. efforts in sharp relief, Cohan said. The World Health Organization announced this month that about 7 million people die each year as a result of air pollution exposure.
Particulate matter consists of microscopic particles spewed into the air by vehicles and industry, as well as particles that form from pollutant gases. "Particulate matter is not a chemical, like ozone; it's a category, and it's a real challenge to figure out the origin of those particles," Cohan said. "Are they sulfates or carbons or nitrates? Each of these needs vastly different control approaches to make a difference."
PM also includes natural emissions from plants, volcanoes, forest fires and desert dust and can be blown across states or even continents.
The health community, Cohan said, has long expressed concerns about particulate matter in the atmosphere and determined in the 1990s that PM 2.5 particles can penetrate deeply into the lungs and cause heart attacks, decrease lung function and even cause premature death. The EPA found healthy people could experience symptoms from exposure to elevated levels of particulate matter and set mandates for regions deemed in 1997 to
|Contact: David Ruth|