Exposure to vehicle traffic in childhood and lung function in young adulthood-a prospective cohort study in an area with low traffic-flows.

Background: Exposure to high levels of vehicle traffic during childhood seems to have a negative effect on lung function. Less is known about the effects of exposure to relatively low levels during childhood. We aimed to study how exposure to vehicle traffic in childhood is associated with lung function and asthma in young adulthood in a 10-year follow-up of a population-based cohort in a municipality with relatively low levels of vehicle traffic.

Methods: The Obstructive Lung Disease in Northern Sweden (OLIN) pediatric cohort II was recruited in 2006 at age 8 years. Exposure to vehicle traffic at baseline was studied in relation to lung function at follow-up at age 19 years (n = 1056 participants). Lung function measures included FEV₁, FVC and FEV₁/FVC. Different exposure thresholds were defined based on proximity (within a 200 m radius from the home address) to a road with a minimum daily count of heavy vehicles (≥ 250 and ≥ 500) or any type of vehicle (≥ 4000 and ≥ 8000). The association between exposure to vehicle traffic at baseline and lung function at follow-up was analyzed by linear regression adjusting for potential confounders.

Results: In general, those above the exposure thresholds had lower lung function than those below, but not significantly so in all comparisons. Those exposed to ≥ 250 heavy vehicles/day had lower mean FEV₁ z-score at follow-up (-0.38) compared with those exposed to < 250 heavy vehicles/day (-0.21), p = 0.033, and this association remained after adjustment for confounders (p = 0.036). Also, those exposed to ≥ 8000 vehicles/day had lower mean FVC z-score (-0.19) than those exposed to < 8000 vehicles/day (-0.02), p = 0.047, with p = 0.032 after adjustment.

Conclusions: Exposure to vehicle traffic in childhood, in a relatively low traffic-flow environment, may be associated with a slightly lower lung function in young adulthood.