On health risks of ambient PM in the Netherlands

Recent studies have presented well-founded assumptions concerning the biological mechanisms involved and the groups of people that are probably more susceptible to PM. Particulate Matter is a generic term for a complex mixture of large and small airborne particles. However, the causal factors within this complex mixture are difficult to disentangle and have not yet been identified. The second Section of this report looks at the different types of PM, their atmospheric behaviour and the methods of measuring them. The health effects associated with PM are also presented. Section 3 discusses the most recent epidemiological, toxicological and human clinical findings and their mutual relationships.

On the basis of epidemiological studies it has been estimated that in the Netherlands some 1,700 to 3,000 people per year die prematurely as a result of inhaling ambient PM. These figures reflect only the effects of acute exposure to air pollution. If the long-term effects of chronic exposure are taken into account, premature mortality could affect 10,000–15,000 people a year in the Netherlands. These last estimates for chronic exposure are more uncertain, because chronic effect studies are much fewer in number. The estimate of the chronic effects was based on foreign studies, which are not completely comparable with the Dutch situation.

Section 4 gives an overview of the most recent information relating to sources of PM and emissions in the Netherlands, while the last Section presents a critical evaluation of the current and future EU standards.

It is recommended that PM10 be retained as a standard for the time being, as it covers the effects of both fine and coarse particles. In view of the emerging evidence implicating fine particles in health effects, it is recommended that a standard for fine PM and/or a source-related fraction be developed as well.

Even with PM concentrations well below European Union (EU) standards, people’s health will still be affected because no threshold has been found for the occurrence of health effects. PM is a complex mixture containing fractions that are to a greater or lesser extent health-relevant. This differentiation in potency has profound implications for an efficient and effective reduction of health impacts through PM emission abatement. PM abatement can be justified by the precautionary principle. Further source- oriented actions could focus on reduction of the total PM10 aerosol mass or, first of all, on those PM fractions that are expected to be more health-relevant. This last option is preferred. These fractions are probably transport-related (diesel soot) and, more generally, combustion- related primary PM emissions. Abatement should therefore focus on these sources. In this respect, the abatement of uncontrolled shipping emissions has been identified as one of the more cost-effective control options. Abatement of other combustion sources such as industrial combustion, wood burning in fireplaces, and off-road machinery are also possible, but less cost-effective.

The European Union has decided on two standards for PM, a daily and an annual average value. The current EU standards for daily and annual average values are not equivalent, as was originally intended. In the Netherlands the following options are equivalent to the EU annual standard of 40 μg/m3: a daily level of 50 μg/m3 with 80 exceedances (while the EU allows 35 exceedances) or a daily level of 100 μg/m3 with 7 permitted exceedances per year. For practical reasons a daily standard of 100 μg/m3 is preferred. Although the EU has proposed two standards for PM, there are several arguments that only one standard would suffice – annual mean concentrations being the best choice. However, for reasons of communication to the public daily standards may be appropriate. Compliance with the annual average EU standard seems feasible for PM10 in the Netherlands in 2005, although local exceedances at ‘hot spots’ cannot be ruled out.

Compliance in 2010 with the indicative annual average EU standard of 20 μg/m3 is not feasible, even at high cost. Expectations are that there will still be 36–40 exceedances per year of the EU daily standard of 50 μg/m3 even after all planned abatement measures (Current Legislation of Emissions (CLE)) have been taken in 2010. Therefore, compliance with the current EU daily standards for 2005 and 2010 does not seem feasible in the Netherlands and adverse health effects will continue to occur.