Are the limit values proposed by the new European Directive 2008/50 for PM2.5 safe for health?

D irective 2008/50 CE of the European Parliament and Council of 21 May 2008 on ambient air quality and cleaner air for Europe was recently approved. 1 Annex XIV of the Directive establishes two stages for particulate matter having a diameter of under 2.5 micron (PM 2.5). Stage 1 indicates that the calendar year limit value for this pollutant is to be 25 mg/m 3 and that the date by which the limit value is to be attained is 1 January 2015. In Stage 2, the calendar year limit value is set at 20 mg/m 3 and is to be attained by 1 January 2020, though the Directive itself indicates that these indicative limit values will be reviewed by the Commission in 2013 in the light of further information on health and environmental effects, technical feasibility and experience of the target value (25 mg/m 3 at 1 January 2010) in Member States. It is evident that PM 2.5 emission levels equal to zero are impossible to achieve in large cities, and that there must be a balance between desirable levels of protection of human health and feasible emission levels. Nevertheless, from the standpoint of their public health effects, the values proposed by this Directive appear to be inappropriate for a number of reasons. First, because in its 2006 guideline levels, 2 the World Health Organization (WHO) itself indicates that, as from an annual average PM 2.5 concentration of 10 mg/m 3 , an increase in mortality due to cardiopulmonary causes is to be expected, establishing that this risk rises by 15% for annual average concentrations of 35 mg/m 3 , whereas premature mortality falls by 6% for levels of 25 mg/m 3 visa `-vis levels of 35 mg/m 3. Furthermore, based on studies undertaken in different US cities 3–5 which associated cancer mortality with PM 2.5 levels for annual average concentrations of 18–20 mg/m 3 , the United States Environmental Protection Agency 6 sets the permitted annual maximum concentration at 15 mg/m 3. Along these same lines are studies conducted in cities, such as Tokyo, 7 which indicate that annual average values of around 12 mg/m 3 would reduce annual mortality in this city by 8%. Within the context of the APHEIS (Air Pollution and Health: A European Information System) network, 8 an assessment—based on different scenarios—was recently made of the long-term effects of annual averages of PM 2.5 concentrations …