Air pollution has been linked to increased mortality risks in many countries, but until now data limitations have prevented a national study in New Zealand. In many towns and cities pollution data come from single monitoring stations, and these give no indication of how exposure might vary across an area. Recently, concentrations of particulate air pollution (PM10) have been modelled for urban areas of New Zealand at a fine resolution, so we can now investigate how pollution varies from neighbourhood to neighbourhood, and how this affects health. We used the pollution data to investigate whether exposure to PM10 was associated with mortality and with greater health inequalities. The study was ecological in design, as it examined the relationship between air pollution and cause-specific mortality within urban Census Area Units (n = 970, population = 2.8 million). The analyses accounted for age, sex, ethnicity, deprivation and smoking behaviour.
We found that PM10 was associated with increased respiratory disease mortality in urban New Zealand, including at concentrations below the existing guideline value of 20 μg.m-3 (the upper concentration advocated for health). Establishing and enforcing a lower guideline value is therefore likely to have population health benefits. However, exposure to PM10 was not associated with increased health inequalities.