Living near traffic is linked to earlier death and adult-onset asthma

Traffic-related air pollution reaches an enormous number of people, both those living beside busy roads and those well beyond them, which makes even modest health effects a major public health issue. The Health Effects Institute had produced a well-cited critical review in 2010, but a decade of new research had accumulated since. The question this new expert panel set out to answer was whether the modern evidence, judged rigorously, still supports links between long-term traffic pollution exposure and serious health outcomes, and how confident we can be in each one.

The institute appointed an expert panel that searched the literature published between January 1980 and July 2019, developed a new exposure framework to decide whether each study was genuinely specific to traffic pollution rather than air pollution generally, and assessed study quality and potential biases. In total 353 studies made the cut. Respiratory effects in children were the most studied outcome with 118 studies, followed by birth outcomes with 86, cardiometabolic effects with 57, adult respiratory effects with 50 and mortality with 48.

The panel reached high or moderate-to-high confidence in associations between long-term traffic pollution exposure and all-cause mortality, circulatory mortality, ischaemic heart disease mortality and lung cancer mortality, as well as asthma onset in both children and adults and acute lower respiratory infections in children. For the other outcomes examined, including birth outcomes and cardiometabolic effects, the evidence was judged moderate, low or very low. The confidence ratings reflect not just the number of studies but their quality and the panel's evaluation of potential biases.

This review updates and strengthens the institute's influential 2010 assessment, moving several outcomes into the higher confidence bands as the evidence base has grown. It also sharpens the field methodologically by insisting on exposure measures specific to traffic rather than pollution in general. What remains open is causation: these are associations drawn from studies that followed populations, and confidence in many outcomes beyond mortality and asthma remains moderate or lower, leaving room for future research to shift the picture.

This is a reason to take where you live, train and commute seriously as a health factor, alongside the usual suspects of diet, exercise and sleep. The strongest links are with the outcomes that matter most: dying earlier, heart disease, lung cancer and developing asthma at any age. The panel's own conclusion was that traffic pollution deserves greater attention from the public and from policymakers, which is informational rather than something an individual can fix alone.