Cardiovascular disease and air pollution in Scotland: no association or insufficient data and study design?

BMC Public Health, Mar 2012

Background Coronary heart disease and stroke are leading causes of mortality and ill health in Scotland, and clear associations have been found in previous studies between air pollution and cardiovascular disease. This study aimed to use routinely available data to examine whether there is any evidence of an association between short-term exposure to particulate matter (measured as PM10, particles less than 10 micrograms per cubic metre) and hospital admissions due to cardiovascular disease, in the two largest cities in Scotland during the years 2000 to 2006. Methods The study utilised an ecological time series design, and the analysis was based on overdispersed Poisson log-linear models. Results No consistent associations were found between PM10 concentrations and cardiovascular hospital admissions in either of the cities studied, as all of the estimated relative risks were close to one, and all but one of the associated 95% confidence intervals contained the null risk of one. Conclusions This study suggests that in small cities, where air quality is relatively good, then either PM10 concentrations have no effect on cardiovascular ill health, or that the routinely available data and the corresponding study design are not sufficient to detect an association.

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Cardiovascular disease and air pollution in Scotland: no association or insufficient data and study design?

Lorna J Willocks 3 Abita Bhaskar 2 Colin N Ramsay 1 Duncan Lee 0 David H Brewster 5 Colin M Fischbacher 5 James Chalmers 5 George Morris 4 E Marian Scott 0 0 School of Mathematics and Statistics, University of Glasgow , Glasgow , UK 1 Health Protection Scotland , Glasgow , UK 2 MRC Social and Public Health Sciences Unit , Glasgow , UK 3 NHS Lothian , Edinburgh , UK 4 NHS Health Scotland , Glasgow , UK 5 Information Services Division, NHS National Services Scotland , Edinburgh , UK Background: Coronary heart disease and stroke are leading causes of mortality and ill health in Scotland, and clear associations have been found in previous studies between air pollution and cardiovascular disease. This study aimed to use routinely available data to examine whether there is any evidence of an association between short-term exposure to particulate matter (measured as PM10, particles less than 10 micrograms per cubic metre) and hospital admissions due to cardiovascular disease, in the two largest cities in Scotland during the years 2000 to 2006. Methods: The study utilised an ecological time series design, and the analysis was based on overdispersed Poisson log-linear models. Results: No consistent associations were found between PM10 concentrations and cardiovascular hospital admissions in either of the cities studied, as all of the estimated relative risks were close to one, and all but one of the associated 95% confidence intervals contained the null risk of one. Conclusions: This study suggests that in small cities, where air quality is relatively good, then either PM10 concentrations have no effect on cardiovascular ill health, or that the routinely available data and the corresponding study design are not sufficient to detect an association. - Background The detrimental effects of air pollution on human health came to public prominence in the mid 1900s, as a result of high pollution episodes in the Meuse valley, Belgium (1930), Donora, Pennsylvania (1948), and London, England (1952). The latter was associated with more than 3,000 excess deaths [1], and was the catalyst for legislation such as the UK Clean Air Act in 1956. Since then, a large number of studies have investigated the health risks from air pollution, and found consistent associations between components of ambient air pollution and measures of ill health. Numerous health endpoints have been considered in such studies, with the most common being mortality [2] and morbidity [3] from respiratory [4] and cardiovascular [5] disease. A number of different pollutants have also been considered in such studies, including, carbon monoxide [6], ozone [7] and both coarse [8] and fine [3] particulate matter. These studies have investigated the effects of both long-term [9] and [10] and short-term [11] and [12] pollution exposure, with the latter typically utilising an ecological time series design. Such time series studies make use of routinely available health and pollution data, and are thus the most common study design because they are inexpensive to conduct. Studies such as those highlighted above provide evidence for the creation of air pollution legislation and guidelines, with examples in the UK being the Clean Air Act (1993) and the Air Quality Strategy (2007). In recent times, the conduit for such studies to effect UK legislation has been the independent Committee On the Medical Effects of Air Pollution (COMEAP), which informs governmental policy by critiquing the evidence provided by such studies. However, surprisingly few of these studies quantify the effects of pollution in the UK, with the majority being based in the USA [12] and [13], mainland Europe [11] and [14] or Asia [15] and [16]. As a result, COMEAP has been forced to base its recommendations to government on studies from further afield, particularly the USA. The transportation of evidence from one continent to another has its own problems (as acknowledged by COMEAP), and suggests that more studies are required to further assess the effects of air pollution in the UK. Furthermore, the studies that have been conducted in the UK have been predominantly based in London [17] and [18], with relatively few assessing the health impact of air pollution in Wales, Northern Ireland or Scotland. In Scotland, studies estimating the short-term effects of pollution are limited to [19] and [20]. The short-term study [19] was based in Edinburgh, and investigated the effects of multiple pollutants, including nitrogen dioxide, ozone and particulate matter, on multiple health endpoints between 1981 and 1995. The results from this study were largely negative, consistently showing no relationship between pollution and ill health. Study [20] extended study [19] to Aberdeen, Edinburgh and Glasgow, the three largest cities in Scotland, and performed a meta-analysis to give overall results for urban Scotland. Their study was based on data from 1981 to 2001, and also failed to find any consistent associations. (...truncated)


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Lorna J Willocks, Abita Bhaskar, Colin N Ramsay, Duncan Lee, David H Brewster, Colin M Fischbacher, James Chalmers, George Morris, E Scott. Cardiovascular disease and air pollution in Scotland: no association or insufficient data and study design?, BMC Public Health, 2012, pp. 227, 12, DOI: 10.1186/1471-2458-12-227