Comparison of averaging techniques for the calculation of the 'European average exposure indicator' for particulate matter.

A comparison of various averaging techniques to calculate the Average Exposure Indicator (AEI) specified in European Directive 2008/50/EC for particulate matter in ambient air has been performed. This was done for data from seventeen sites around the UK for which PM(10) mass concentration data is available for the years 1998-2000 and 2008-2010 inclusive. The results have shown that use of the geometric mean produces significantly lower AEI values within the required three year averaging periods and slightly lower changes in the AEI value between the three year averaging periods than the use of the arithmetic mean. The use of weighted means in the calculation, using the data capture at each site as the weighting parameter, has also been tested and this is proposed as a useful way of taking account of the confidence of each data set.

Twenty-five years of nationwide ambient metals measurement in the United Kingdom: concentration levels and trends.

Ambient air quality has been an important issue for humans and the environment for hundreds of years. More recently, definitive links have been identified between pollutants and adverse effects on human health and on environmental sustainability. Of particular concern since the last quarter of the twentieth century has been the presence of toxic 'heavy metals' in ambient air. In order to measure the concentrations of pollutants, including 'heavy metals', in ambient air, to assess human and environmental exposure, comply with developing legislation, and assess newly introduced abatement strategies, the UK government established nationwide air quality measurement networks in the late 1970s. The nationwide measurement of 'heavy metals' in ambient air began in the late 1970s, and in 1980 was developed into several national networks, aimed at different metals and different emissions sources. These networks were rationalised into the current UK Heavy Metals Monitoring Network in 2003. The data produced by the current scientific operator of the Network, the National Physical Laboratory (NPL), in 2005, marked 25 years of ambient 'heavy metals' measurement in the UK at a nationwide level. This paper celebrates this milestone and provides a novel and critical examination of Network operations, measured concentration levels, and trends, over the last quarter of a century.