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 Another recent unpublished study (13) used a case-control design to examine childhood exposure to smoke and sulphur dioxide air pollution in adults born in the 1930s and death from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.

(2) Dockery DW, Arden Pope CI, Xu X, et al. An association between air pollution and mortality in six US cities. New Engl J Med 1993;329:1753-9.

(3) Abbey DE, Nishino N, McDonnell WF, et al. Long-term inhalable particles and other air pollutants related to mortality in nonsmokers. Am J Respir Crit Care Med 1999;159:373-82.

(4) Pope CA3, Burnett RT, Thun MJ, et al. Lung cancer, cardiopulmonary mortality and long-term exposure to fine particulate air pollution. J Am Med Assoc 2002;287:1132-41.

(5) Hoek G, Brunekreef B, Goldbohm S, et al. Association between mortality and indicators of traffic-related air pollution in the Netherlands: a cohort study. Lancet 2002;360:1203-9.

(6) Daley C. Air pollution and causes of death. Br J Prev Soc Med 2003;13:14-27.

(7) Stocks P. Cancer and bronchitis mortality in relation to atmospheric deposit and smoke. Br Med J 1959;i:74-9.

(8) Gardner M, Crawford M, Morris J. Patterns of mortality in middle age and early old age in the county boroughs of England and Wales. Br J Prev Soc Med 1969;23:133-40.

(9) Chinn S, Baldwin I, Gorgol M. The relation of mortality in England and Wales 1969-73 to measurements of air pollution. J Epidemiol Community Health 1981;35:174-9.

(10) Shaddick G, Wakefield J, Briggs D, Elliott P. Modelling the association between mortality and long term exposure to air pollution (Abstract 10447). Epidemiology 2002;13.

(11) Krewski D, Burnett RT, Goldberg MS, et al. Reanalysis of the Harvard Six Cities Study and the American Cancer Society Study of Particulate Air Pollution and Mortality. Cambridge, MA: Health Effects Institute 2000.

(12) Sloggett A,.Downing A. The effects of total water hardness, smoke particles and sulphur dioxide levels on mortality in urban areas of England and Wales. Geographica Polonica 1995;64:177-86.

(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.

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