Long-term associations of outdoor air pollution with mortality in Great Britain

Abstract

Background: Recent studies have indicated long-term effects on mortality of particulate and sulphur dioxide (SO₂) pollution, but uncertainties remain over size of any effects, potential latency and generalisability.

Methods: Small-area study across electoral wards in Great Britain of mean annual black smoke (BS) and SO₂ concentrations (from 1966) and subsequent all cause and cause-specific mortality. Use of random effect models within a Bayesian framework, adjusted for social deprivation and urban/rural classification. Different latencies and changes in associations over time were assessed.

Results: We found significant associations of BS and SO₂ concentrations with mortality. Effects were stronger for respiratory illness than other causes of mortality, for the most recent exposure periods (shorter latency times) and most recent mortality period (lower pollutant concentrations). In pooled analysis across four sequential four-year mortality periods (1982-98), adjusted excess relative risk for respiratory mortality was 3.6% (95% CI 2.6-4.5%) per 10 µg/m³ BS, and 13.2% (11.5-14.9 %) per 10 ppb SO₂, and in the most recent period (1994-98) it was 19.3% (5.1-35.7%) and 21.7% (2.9-38.5%) respectively.

Conclusions: Our findings add to the evidence that air pollution has long-term effects on mortality, and point to continuing public health risks even at the relatively lower levels of BS and SO₂ that now occur. They thus have importance for policies on public health protection through regulation and control of air pollution.