Air pollution from industries and asthma onset in childhood: A population-based birth cohort study using dispersion modeling

Background: Despite evidence that ambient air pollution may play a role in the development of asthma, little is known about the potential contribution of industrial emissions.

Objective: We used a population-based birth cohort to investigate the association between asthma onset in childhood and residential exposure to industrial emissions, estimated from atmospheric dispersion modeling.

Methods: The study population comprised all children born in the province of Quebec, Canada, 2002-2011. Asthma onset were ascertained from health administrative databases with validated algorithms. We used atmospheric dispersion modeling to develop time-varying annual mean concentration of ambient PM_2.5, NO₂ and SO₂ at participants' residence from industries. For each pollutant, we assessed the association between industrial emissions exposure and childhood asthma onset using Cox proportional hazard model, adjusted for sex, material and social deprivation and calendar year. Sensitivity analysis included adjusting for long-term regional and traffic-related ambient PM_2.5 and NO₂, and assessing potential confounding by unmeasured secondhand smoke.

Results: The cohort included 722,667 children and 66,559 incident cases of asthma. For all pollutants, we found a non-linear association between childhood asthma onset and residential ambient air pollutant concentration from industries, with stronger effects at lower concentrations. A change from 25th to the 75th percentile in the mean annual ambient concentration of PM_2.5 (0.13 μg/m³), NO₂ (1.0 μg/m³) and SO₂ (1.6 μg/m³) from industrial emissions was associated with a 19% (95% CI: 17-20%), 21% (95% CI: 19-23%) and 23% (95% CI: 21-24%) increase in the risk of asthma onset in children, respectively. For PM_2.5 and NO₂, associations were persisting after adjustments for long-term regional PM_2.5 and traffic-related NO₂ ambient concentration.

Conclusion: Residential exposure to industrial emissions estimated from dispersion modeling was associated with asthma onset in childhood. Importantly, associations were stronger at lower concentrations and independent from those of other sources, thus adding up to the burden of regional and traffic-related air pollution.