Much of the air pollution that damages human health and the environment today is the result of human activities. But natural sources also emitt air pollutants, contributing to the exposure of European citizens and ecosystems to bad air quality — and potentially undermining EU Member State efforts to meet the air quality standards set out in EU legislation.
Recognising the challenge presented by natural air pollution, the Air Quality Directive (1) provides that before Member States compare ambient air pollutant concentrations with relevant legally binding limit values they may subtract the contribution of natural sources.
This report provides a first evaluation of Member State reporting on natural air pollution under the Air Quality Directive. Its main objectives are:
- to provide an overview of the main natural sources of air pollutants;
- to summarise methods that can be used to quantify natural source contributions to air pollution levels;
- to analyse Member State reporting on natural air pollutant contributions to limit value exceedances for the years 2008 and 2009;
- to identify recommendations for improvements, particularly proposals relevant to current efforts to develop an electronic reporting mechanism on natural source contributions.
Natural sources of particulate matter
European Commission Staff Working Paper 6771/11 (EC, 2011a) provides guidance on which sources can be regarded as 'natural' and on methods to quantify and subtract the contribution of these sources in the framework of the Air Quality Directive. The Working Paper also defines principles to be applied when evaluating Member State reporting of exceedances due to natural contributions. It does not specify the pollutants for which an exception on natural sources may be requested.
Completed reporting questionnaires for the years 2008 and 2009 reveal that particulate matter (PM10) was the only natural contribution to limit value exceedances reported by Member States. Since natural PM10 sources affect health and the environment, it is important that Member States consider all appropriate measures to reduce excessive exposure and ensure accurate reporting of such natural air pollutant contributions.
According to the Staff Working Paper, when PM10 limit values are exceeded, contributions from the following natural sources may be subtracted:
- Wind-blown desert dust, i.e. natural particulate matter transported from dry regions. Arid zones in North Africa are the major source in the European Union.
- Sea spray aerosols, which are finely dispensed particles emitted from the sea surface.
- Particulate matter emitted by volcanos and seismic activities.
- Particulate matter emitted by wild-land fires. Such fires are caused by burning non-managed and managed forests and other vegetation, excluding agricultural burning of stubbles etc.
A pollution source can only be considered 'natural' if it involves no direct or indirect human activity. This can hamper attempts to justify air pollution resulting from events that can occur with or without human intervention, such as wild-land fires.