Air pollution and human health: a phenome-wide association study

To explore the associations of long-term exposure to air pollution with onset of all human health conditions.

Prospective phenome-wide association study.

Denmark.

All Danish residents aged ≥30 years on 1 January 2000 were included (N=3 323 612). After exclusion of individuals with missing geocoded residential addresses, 3 111 988 participants were available for the statistical analyses.

First registered diagnosis of every health condition according to the International Classification of Diseases, 10th revision, from 2000 to 2017.

Long-term exposure to fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) were both positively associated with the onset of more than 700 health conditions (ie, >80% of the registered health conditions) after correction for multiple testing, while the remaining associations were inverse or insignificant. As regards the most common health conditions, PM_2.5 and NO₂ were strongest positively associated with chronic obstructive pulmonary disease (PM_2.5: HR 1.06 (95% CI 1.05 to 1.07) per 1 IQR increase in exposure level; NO₂: 1.14 (95% CI 1.12 to 1.15)), type 2 diabetes (PM_2.5: 1.06 (95% CI 1.05 to 1.06); NO₂: 1.12 (95% CI 1.10 to 1.13)) and ischaemic heart disease (PM_2.5: 1.05 (95% CI 1.04 to 1.05); NO₂: 1.11 (95% CI 1.09 to 1.12)). Furthermore, PM_2.5 and NO₂ were both positively associated with so far unexplored, but highly prevalent outcomes relevant to public health, including senile cataract, hearing loss and urinary tract infection.

The findings of this study suggest that air pollution has a more extensive impact on human health than previously known. However, as this study is the first of its kind to investigate the associations of long-term exposure to air pollution with onset of all human health conditions, further research is needed to replicate the study findings.