Urban areas annualized levels

The Mediterranean Basin is highly influenced by shipping emissions due to its extremely busy shipping routes. These emissions may account for 2 1% of the mean annual ambient air PM10 levels (25% primary particles and 75% secondary particles) and for 14% of the mean annual PM2.5 in Mediterranean urban areas [51]. It has been estimated that 54% of the total sulphate aerosol column burden over the Mediterranean in summer originates from ship emissions [52],... 

Air quality in urban areas continues to be a growing concern on account of its health and environmental impact. Many cities across the world are experiencing high levels of air pollution due to emissions resulting mainly from road traffic (Sokhi 2005). Among the numerous pollutants that affect air quality, PM is the most widespread threat to health. For this reason many countries have imposed air quality standards to establish permissible levels. EU standards (EU Directive 1999/30/EC) are based on annual and daily limit values for PMio levels of 40 and 50 pg/m, respectively. However, the EU Directive 2008/50/EC established that a Member State can be exempt from the obligation to apply the limit values until 11 June 2011 when these cannot be achieved because of site-specific dispersion characteristics, adverse climatic conditions or transboundary contributions. 

The rationale for the choice of the annual average guideline value of 10 pg/m for PM2.5 was that it represents the lower end of the range over which significant effects on survival have been observed in the American Cancer Society Study (ACS) (Pope et al. 2002). Further discussion on this can be found in the document (WHO 2005), which also concludes that although adverse effects on health cannot be entirely ruled out even below that level, it is a level achievable in urban areas of developed countries, and therefore attainment to it is expected to effectively reduce the health risks. However, the experts emphasized the need to reduce exposure to non-threshold pollutants such as particulate matter, even where current concentrations are close to or below the proposed guidelines. 

In the majority of European countries, the simulated concentrations of PCBs exceeded 0.1 ng m . Minimum concentrations from 0.025 to 0.05 ng m are characteristic for remote regions (Ireland, Iceland, Sweden, Norway, and Finland). In the early 1990s, the mean annual concentration of PCBs in the urban air in London was 1.3 ng m [10] and the average at one site in Paris was 1.2 ng m [68,69]. The PCB level in the air of 0.03-0.09 ng m measured in the Mediterranean basin at the island of Crete (Greece) was indicated as one of the lowest in the world [69]. The wet deposition of PCBs was determined at six sites, including remote island, rural and urban areas in northern France from October 1999 to October 2000 and variations from 3 to 2,300 ng m M" as Aroclor equivalents in the weekly samples were found. The maximum yearly deposition was measured at the site with high rain fallout [69]. 

Data fi om Environment Canada indicate that the annual average level of airborne particles at all NAPS monitoring sites decreased by 46 percent between 1974 and 1986. This significant improvement in urban air quality relative to particulate emissions reductions refiects the fact that most major industrial sources of particulate matter are located outside urban areas. The average levels at more than 90 percent of the sites were well within the desirable range of air quality in 1986 (Fig. P-2). 

In urban areas of Canada, the annual average level of suUur dioxide measured at NAPS monitoring sites decreased by 54 percent between 1974 and 1986— from 13 ppb to 6 ppb—and the annual average levds at 90 percent of the NAPS monitoring sites are now well below the maximum desirable level annual air quality objective of 10 ppb (Fig. P-4). In 1986, the one-hour maximum desirable level... 

Similar downward trends in PMI() have been observed at surface measuring sites in the United States in urban, suburban, and rural areas. Figure 16.44, for example, shows the trends in the annual average PMI() levels in these three types of air environments (Darlington et al., 1997). Reductions of 3-4% per year have been observed. Simultaneously, the annual average gas-phase concentrations of S02 and NOx, precursors to sulfate and nitrate in particles, decreased. Downward trends of —1.6—1-8% per year in the optically active aerosol over the United States has also been reported (e.g., Hofmann, 1993). 

Table 14 Population weighted exposure to annual mean and 36th highest daily mean levels in urban and regional background areas in pg/m3 (source ETC/ACC [4])...

Very approximately it is estimated that some 30-50% reduction in emissions from new boilers and 70% of existing boilers in the EEC can be achieved at total annual average costs between 0.1-0.4 X 10 per annum by the year 2000. This level of emissions control on static emitters would reduce total availability of in the atmosphere by some 9-12%. In urban and industrial areas, the reduction in local ambient NO concentrations would probably be substantially more, perhaps 15-25%, assuming vehicle NO emissions were also reduced in line with the current programme. Fitting flue gas scrubbers to control SO2 emissions would also reduce NO emissions substantially (70-80% removal), so that the two sets of costs should not be considered additive. 

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