J Epidemiol Community Health 66:468-473 doi:10.1136/jech.2010.112490
  • Research report

Air pollution and mortality in New Zealand: cohort study

Open Access
  1. Alistair Woodward3
  1. 1Department of Public Health, University of Otago, Wellington, New Zealand
  2. 2University of Otago, Wellington, New Zealand
  3. 3University of Auckland, Auckland, New Zealand
  1. Correspondence to Dr Simon Hales, Department of Public Health, University of Otago, Wellington, 23a Mein Street, Wellington 6242, New Zealand; simon.hales{at}
  1. Contributors TB conceived the analysis and contributed to the design, interpretation and revision of drafts. SH performed the analyses, drafted the text of the paper and contributed to the design and interpretation of results. SH had full access to the data, and takes responsibility for the integrity of the analysis and the accuracy of the results. AW contributed to study design, the interpretation of results and revision of drafts.

  • Accepted 8 July 2010
  • Published Online First 21 October 2010


Background Few cohort studies of the health effects of urban air pollution have been published. There is evidence, most consistently in studies with individual measurement of social factors, that more deprived populations are particularly sensitive to air pollution effects.

Methods Records from the 1996 New Zealand census were anonymously and probabilistically linked to mortality data, creating a cohort study of the New Zealand population followed up for 3 years. There were 1.06 million adults living in urban areas for which data were available on all covariates. Estimates of exposure to air pollution (measured as particulate matter with an aerodynamic diameter less than 10 μm, PM10) were available for census area units from a previous land use regression study. Logistic regression analyses were conducted to investigate associations between cause-specific mortality rates and average exposure to PM10 in urban areas, with control for confounding by age, sex, ethnicity, social deprivation, income, education, smoking history and ambient temperature.

Results The odds of all-cause mortality in adults (aged 30–74 years at census) increased by 7% per 10 μg/m3 increase in average PM10 exposure (95% CI 3% to 10%) and 20% per 10 μg/m3 among Maori, but with wide CI (7% to 33%). Associations were stronger for respiratory and lung cancer deaths.

Conclusions An association of PM10 with mortality is reported in a country with relatively low levels of air pollution. The major limitation of the study is the probable misclassification of PM10 exposure. On balance, this means the strength of association was probably underestimated. The apparently greater association among Maori might be due to different levels of co-morbidity.


  • Statistics New Zealand Security Statement The New Zealand Census Mortality Study is a study of the relation between social factors and mortality in New Zealand, based on the integration of anonymised population census data from Statistics New Zealand and mortality data from the New Zealand Health Information Service. This project was approved by Statistics New Zealand as a data laboratory project under the Microdata Access Protocols in 1997. The datasets created by the integration process are covered by the Statistics Act and can be used for statistical purposes only. Only approved researchers who have signed Statistics New Zealand's declaration of secrecy can access the integrated data in the data laboratory. Access to the data used in this study was provided by Statistics New Zealand under conditions designed to give effect to the security and confidentiality provisions of the Statistics Act, 1975. The results presented in this study are the work of the author, not Statistics New Zealand. The authors take full responsibility for the paper and Statistics New Zealand will not be held accountable for any error or inaccurate findings.

  • Funding The study was funded by the National Institute of Water and Atmospheric Research (NIWA). The New Zealand Census Mortality Study is conducted in collaboration with Statistics New Zealand and within the confines of the Statistics Act 1975. The New Zealand Census Mortality Study study was funded by the Health Research Council of New Zealand, and receives continuing funding from the Ministry of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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