Chronic health effects of air pollution on respiratory and cardiovascular mortality in the UK
Anna Hansell and Paul Elliott, Imperial College London, David Strachan, St George's Hospital, London and Ravi Maheswaran, University of Sheffield
[Project number 30101]
The Committee on the Medical Effects of Air Pollution (COMEAP) has commented
on the relative lack of studies on chronic health effects of air pollution
and on the need for studies in the UK as the quantitative relationship
between air pollution and mortality may vary between countries. (1)
The UK has a unique long-running set of air pollution data, but these
have not been widely used in health studies. Most of the recent information
on chronic effects of air pollution has been obtained from four American
and Dutch cohort studies (2-5). Some broad scale studies were conducted
in the UK in the 1950s to 1970s (6-9) but these did not control for individual-level
confounders. Few recent UK studies have been conducted. One such study
(10) examined associations between mortality in 1982-1998 and cumulative
air pollution in approximately 400 wards containing an air pollution monitoring
station. Unlike the American studies (11), this study predominantly found
effects on respiratory rather than cardiovascular mortality. Adjustments
were made for ward-level deprivation, but control for individual-level
confounders was not possible.
Two recently conducted analyses have used the Longitudinal Study cohort. Sloggett and Downing (12) related smoke and sulphur dioxide exposures based on place of residence in the 1971 to all-cause mortality in 1974-1989, using count data. All associations disappeared after adjustment for socio-economic factors. Limitations of this study include the use of air pollution exposure measures grouped into tertiles relating to a single time point. Also, cause-specific mortality was not examined. Another recent unpublished study (13) used a case-control design to examine childhood exposure to smoke and sulphur dioxide air pollution in adults born in the 1930s and death from chronic obstructive pulmonary disease or lung cancer in 1994-96. Associations persisted after adjustment for individual and area level confounders. However, this study did not examine effects of exposure in adult life.
The aim of this proposal is to establish whether estimated cumulative
air pollution exposures in adult life are associated with cardiovascular
and respiratory deaths in the UK.
Permission is sought to conduct individual level analyses on anonymised data at ONS. Area-based air pollution measures will first be constructed from monitoring station data for the last 50 years, using methodology adapted from the European Union funded APMoSPHERE project (http://www.sahsu.org/related_studies.html). These air pollution measures will be linked to area of residence of Longitudinal Study (LS) members at each Census and related to later death from cardio-respiratory disease. As the LS is one of the largest long-running UK cohorts, there will be enough power to examine cause-specific mortality. For example, people with chronic obstructive pulmonary disease (COPD) may be particularly susceptible to air pollution. The LS is the only UK cohort where members are old enough to have died of COPD in sufficient numbers to examine this. The 40 years of follow-up will allow estimation of cumulative effects of air pollution. The numbers involved, length of follow-up and ability to control for individual level confounders will make this the most authoritative UK study to date on the chronic effects of air pollution.
(1) Committee on the Medical Effects of Air Pollution. Statement on long-term
effects of particulates on mortality http://www.doh.gov.uk/comeap/statementsreports/longtermeffects.pdf
2001. London, Dept of Health.
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Six Cities Study and the American Cancer Society Study of Particulate
Air Pollution and Mortality. Cambridge, MA: Health Effects Institute 2000.
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(13) Strachan, D. and Maheswaran, R. Air pollution exposure in childhood and fatal chronic respiratory disease: a nationwide case-control study. (Personal communication) Summary at http://www.doh.gov.uk/comeap/statementsreports/comeapjan0101.pdf page 13.