The health effects of air pollution are attracting ever greater international interest. Air pollution is one of the greatest causes of DALY loss according to the Global Burden of Diseases report, accounting for 141.5 million DALYs in 2013, and 5.5 million deaths. However, studies to date have been mostly ecological. That is to say, they compare outcomes for people living in areas with different levels of exposure, not by the individual’s level of exposure.
The US-based Multi-Ethnic Study of Atherosclerosis and Air Pollution (MESA Air) measures exposure to pollution over time. A validated method is used to measure long-term exposure based on sampling in and around individual homes, as well as at the ecological level. Exposure to small (<2.5µm) particles and nitrogen oxide (NO2) was measured over a ten year period. Exposure to each pollutant was related to two markers of atherosclerosis – changes in cardiac artery calcification and in carotid artery intimal-medial thickness. The statistical analysis adjusted for individual factors, such as statin use. Calcification of coronary arteries is a validated surrogate for heart attack, and the prevalence of such calcification was positively correlated with both types of pollution. Cause and effect inference is strengthened by the finding that living near to large road was a risk factor for coronary calcification. No change was noted in the carotid artery, but intimal-medial thickness is a far less valid surrogate for stroke than is carotid calcification for heart attack.
— Richard Lilford, CLAHRC WM Director
- Global Burden of Diseases 2013 Risk Factor Collaborators. Global, regional, and national comparative risk assessment of 79 behavioural, environmental and occupational, and metabolic risks or clusters of risks in 188 countries, 1990–2013: a systematic analysis for the Global Burden of Disease Study 2013. Lancet 2015; 386: 2287-323.
- Kaufman JD, Adar SD, Barr RG, et al. Association between air pollution and coronary artery calcification within six metropolitan areas in the USA (the Multi-Ethnic Study of Atherosclerosis and Air Pollution): a longitudinal cohort study. Lancet. 2016; 388: 696-704.