Cleaner Air Linked To Reduced Death Rates

Two population studies in this week’s issue of THE LANCET highlight how poor air quality is directly related to increased risk of death from respiratory and cardiovascular disease.

Luke Clancy from St James Hospital, Dublin, and colleagues from Trinity College and Dublin Institute of Technology, Dublin, Ireland, and Harvard School of Public Health, Boston, USA, examined the effect of the 1990 coal ban in Dublin on population death-rates in the six years before and after the ban was introduced. The average concentrations of black smoke decreased by 70% (36 micrograms per cubic meter) after the ban on coal sales; this was associated with an overall decrease in non-trauma death rate of nearly 6%, in which death by respiratory causes decreased by around 15%, and by cardiovascular causes by around 10%. This related to an estimated reduction of 116 respiratory deaths and 243 cardiovascular deaths every year after the ban was implemented. Numerous studies have confirmed that increased air-pollution concentrations increase mortality but this study shows that decreasing air pollution is associated with a marked reduction in mortality.

In a second study, a research team from the Netherlands assessed the relation between traffic-related air pollution and death based on data from participants of an ongoing study (the Netherlands Cohort study on Diet and Cancer [NLCS]). 5000 people from the NLCS (age 55-69 years) were studied from 1986 to 1994. Long-term exposure to traffic-related air pollutants (black smoke and nitrogen dioxide) was estimated for the home address in 1986 of each participant. 11% of the study population died during follow-up; people who lived near a main road were around twice as likely to die from cardiopulmonary disease (affecting heart and / or lungs), and were 1.4 times more likely to die from any cause. However, excluding death from cardiopulmonary disorder or lung cancer, there were no other cause-specific associations between pollution exposure and mortality.

In an accompanying Commentary (p 1184), Annette Peters from the National Research Centre for Environment and Health, Neuherberg, Germany, concludes: “Clearly further research is needed, but the research reported today has direct relevance to public-health policy, since both coal-burning and traffic emissions continue to be major sources of particulate exposure worldwide. Emission control and effective local interventions are needed to lighten the health burden of particulate air-pollution everywhere.”