Mortality risk from long-term exposure to traffic pollution

By Joanna Lyford, Senior medwireNews Reporter

Long-term exposure to air pollution is associated with increased rates of all-cause, cardiopulmonary, and lung cancer mortality, a large German study indicates.

The same risks were also increased for people who lived close to major roads, presumably reflecting exposure to air pollutants originating from motor vehicle traffic.

Writing in Occupational & Environmental Medicine, Joachim Heinrich (German Research Center for Environmental Health, Neuherberg) et al say that their findings strengthen the evidence that long-term exposure to particulate matter and traffic-related air pollution increases mortality.

The research was undertaken by Heinrich and team, who analyzed data on 4752 women living in North Rhine-Westphalia. The women were aged 50-59 years on enrolment between 1985 and 1994 and were followed up for a median of 18.4 months.

Heinrich et al assessed the women's exposure to air pollution in two ways: from the distance between their residential address and the nearest major road, and by calculating average particulate matter concentrations below 10 mm (PM₁₀) and nitrogen dioxide (NO₂) levels using data from the nearest air-monitoring station.

During follow up a total of 740 women died; one-third of deaths were from cardiovascular causes, while respiratory causes (4.7%) and lung cancer (5.5%) were less common. Exposure to PM₁₀ and NO₂ varied widely, from 34.8 to 52.5 mg/m³ and 20 to 60 mg/m³, respectively, the authors note, and levels fell dramatically after 1985.

Analysis revealed that each 7-µg/m³ increase in PM₁₀ was associated with increased risks for all-cause, cardiopulmonary, and lung cancer mortality, with hazard ratios (HRs) of 1.15, 1.39, and 1.84, respectively.

Similarly, each 16-µg/m³ increase in NO₂ exposure was associated with increased risks for all-cause and cardiopulmonary mortality, with HRs of 1.18 and 1.55, respectively.

Also, living within 50 meters of a major road was associated with increased relative risks for all-cause, cardiopulmonary, and respiratory mortality.

Heinrich and colleagues conclude: "Our study results and the findings of other cohorts are strongly consistent, despite differences in study design, study populations, sources of ambient air pollution, exposure assessments, climatic conditions and more general differences regarding space and time, which highlights the robustness of the association between long-term exposure to ambient air pollution and mortality."

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