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

DESIGN: Prospective phenome-wide association study.

SETTING: Denmark.

PARTICIPANTS: 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.

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

RESULTS: Long-term exposure to fine particulate matter (PM 2.5) and nitrogen dioxide (NO 2) 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 NO 2 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; NO 2: 1.14 (95% CI 1.12 to 1.15)), type 2 diabetes (PM 2.5: 1.06 (95% CI 1.05 to 1.06); NO 2: 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); NO 2: 1.11 (95% CI 1.09 to 1.12)). Furthermore, PM 2.5 and NO 2 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.

CONCLUSIONS: 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.