A policy change as a natural experiment
Clancy and colleagues compared Dublin’s air pollution and mortality for 72 months before and after the 1990 coal-sales ban. Their interrupted time-series analysis adjusted for weather, respiratory epidemics and mortality elsewhere in Ireland. This evaluated a community intervention, not a household device or an individual change in behaviour.
What the 2002 analysis reported
Black-smoke concentrations fell by about 70%. Adjusted non-trauma mortality decreased by 5.7%, respiratory mortality by 15.5% and cardiovascular mortality by 10.3%. These were changes in population rates around the intervention, not a guaranteed benefit for each resident or a percentage reduction attributable to one pollutant in isolation.
The later analysis matters
A before-and-after study must distinguish the intervention from background health, economic and social trends. HEI’s 2013 reassessment retained evidence of reduced respiratory mortality after the Dublin ban but did not find reductions in total or cardiovascular mortality. The early estimates should not be presented without that qualification.
Read the evidence as it develops
Dublin illustrates both the value of evaluating cleaner-air policies and the importance of revisiting methods. Read the companion HEI article before quoting the early mortality percentages. Neither report supplies a prediction of how much an individual’s risk changes after a day of cleaner air.
Sources
- Clancy L, Goodman P, Sinclair H, Dockery DW. Effect of air-pollution control on death rates in Dublin, Ireland: an intervention study. The Lancet (2002). DOI: 10.1016/S0140-6736(02)11281-5 ↗
- Dockery DW, Rich DQ, Goodman PG, et al.. Effect of Air Pollution Control on Mortality and Hospital Admissions in Ireland. Health Effects Institute, Research Report 176 (2013) ↗
Educational information; personal health questions belong with your clinician.
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