Air quality experts advise that particle size measurements should remain at 10 microns

The Expert Panel on Air Quality Standards had been asked by the Government to consider whether there should be a change in the air quality standard for the UK in the light of recent evidence that the toxicity of ambient aerosols may lie in the fraction of particles of 2.5 microns or less (see related story), and that the 10 micron fraction may include re-suspended dust of low toxicity.

Despite this evidence, however, the Panel found that epidemiological research points to the two fractions being very closely correlated, and that their health effects are inseparable. The Panel also uncovered uncertainties over the reliability of measurements of the smaller fraction due to the loss of volatile material. This meant that they were able to conclude in their report, What is the appropriate Measurement on which to base a standard?, that the current measurement of 10 micron particles provides adequate protection of the health of the public.

“I am very grateful for the Panel’s work,” said Environment Minister Keith Hill. “Their comprehensive consideration of the evidence is an important contribution to the field, and provides a sound basis for the development of our policy on airborne particles.”

Despite their recommendation, however, the Panel are also calling for greater research into pollution from particulates, in order to develop a better definition and measurement of the toxic components of the particulate aerosol, and also for further epidemiological studies investigating the relationship between different components and health effects.

“The Panel’s conclusion, that our current focus for regulation (PM10) is still appropriate, will be an important contribution to the review of the national air quality objective for articles which is now underway,” Hill added. “I think its absolutely right that our independent experts be asked to keep this fast moving subject area under active review, and that our air quality research programme should help provide information to help the Panel with this task.”