22 September 2006

The US Environmental Protection Agency (EPA) announced new, revised National Ambient Air Quality Standards (NAAQS) for fine and coarse particle matter, referred to as PM2.5 and PM10, respectively (fine particles are 2.5 micrometers in diameter and smaller; inhalable coarse particles have diameters between 2.5 and 10 micrometers).

The main provisions of the new rule are:

  • The EPA has strengthened its previous daily PM2.5 standard, from 65 µg/m3 to 35 µg/m3.
  • The current annual PM2.5 standard remains unchanged at 15 µg/m3.
  • The existing daily PM10 standard remains at 150 µg/m3.
  • The annual PM10 standard has been revoked; the available evidence does not suggest an association between long-term exposure to coarse particles at current ambient levels and health effects, said the EPA.

States must meet the revised standards by 2015, with a possible extension to 2020, depending on local conditions and the availability of controls. Later this month, EPA will issue guidance on monitoring fine and coarse particle pollution.

EPA Administrator Stephen Johnson touted the rules as “the most protective air quality regulations in US history”. However, a number of environmental groups have criticized the new standards as inadequate.

Source: US EPA