21 December 2004

The US Environmental Protection Agency (EPA) has designated areas for the Fine Particle National Ambient Air Quality Standards. The EPA designated 224 counties (including some partial counties) in 20 states, as well as the District of Columbia, as PM2.5 nonattainment (i.e., out of compliance) areas. This marks the beginning of the enforcement of air quality standards for fine particles (PM2.5), defined as particles with a diameter below 2.5 µm.

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Most of the non-compliant counties are in the Midwest, Northeast, in Southern California, and near Atlanta, GA. The main PM2.5 source in the Midwest and in some of the Northeast areas is coal-fired power generation. Transportation, including diesels, is an important source in several of the remaining areas.

Under the US Clean Air Act, states with PM2.5 nonattainment areas will have to prepare State Implementation Plans (SIP) by early 2008 outlining what actions will be taken to reduce pollution. They are expected to attain clean air not later than 2010-2015. This will likely trigger a number of new diesel retrofit/replacement programs in those of the affected areas where diesels are important contributors to the ambient PM2.5 levels. However, many of the nonattainment areas are expected to achieve compliance due to emission regulations from power plants and from diesel engines that have been adopted in the recent years. According to the recently published EPA 2003 Particle Pollution Report, PM2.5 levels are now the lowest since nationwide monitoring began in 1999. Since 1999, monitored concentrations of PM2.5 have decreased 10% and are about 30% lower than EPA estimates of levels 25 years ago.

Source: US EPA