Environmental exposure to industrial air pollution is associated with decreased male fertility

Abstract

Objective: To understand how chronic exposure to industrial air pollution is associated with male fertility through semen parameters.

Design: Retrospective cohort study.

Patients: Men in the Subfertility, Health, and Assisted Reproduction cohort who underwent a semen analysis in the two largest healthcare systems in Utah from 2005-2017 with ≥1 measured semen parameter (N = 21,563).

Intervention(s): Residential histories for each man were constructed using locations from administrative records linked through the Utah Population Database. Industrial facilities with air emissions of nine endocrine-disrupting compound chemical classes were identified from the Environmental Protection Agency Risk-Screening Environmental Indicators microdata. Chemical levels were linked with residential histories for the 5 years before each semen analysis.

Main outcome measures: Semen analyses were classified as azoospermic or oligozoospermic (< 15 M/mL) using World Health Organization cutoffs for concentration. Bulk semen parameters such as concentration, total count, ejaculate volume, total motility, total motile count, and total progressive motile count were also measured. Multivariable regression models with robust standard errors were used to associate exposure quartiles for each of the nine chemical classes with each semen parameter, adjusting for age, race, and ethnicity, as well as neighborhood socioeconomic disadvantage.

Results: After adjustment for demographic covariates, several chemical classes were associated with azoospermia and decreased total motility and volume. For exposure in the 4th relative to 1st quartile, significant associations were observed for acrylonitrile (β_{total motility} = -0.87 pp), aromatic hydrocarbons (odds ratio [OR]_azoospermia = 1.53; β_volume = -0.14 mL), dioxins (OR_azoospermia = 1.31; β_volume = -0.09 mL; β_{total motility} = -2.65 pp), heavy metals (β_{total motility} = -2.78pp), organic solvents (OR_azoospermia = 1.75; β_volume = -0.10 mL), organochlorines (OR_azoospermia = 2.09; β_volume = -0.12 mL), phthalates (OR_azoospermia = 1.44; β_volume = -0.09 mL; β_{total motility} = -1.21 pp), and silver particles (OR_azoospermia = 1.64; β_volume = -0.11 mL). All semen parameters significantly decreased with increasing socioeconomic disadvantage. Men who lived in the most disadvantaged areas had concentration, volume, and total motility of 6.70 M/mL, 0.13 mL, and 1.79 pp lower, respectively. Count, motile count, and total progressive motile count all decreased by 30-34 M.

Conclusion(s): Several significant associations between chronic low-level environmental exposure to endocrine-disrupting compound air pollution from industrial sources and semen parameters were observed. The strongest associations were seen for increased odds of azoospermia and declines in total motility and volume. More research is needed to further explore additional social and exposure factors as well as expand on the risk posed to male reproductive health by the studied chemicals.

Keywords: Male fertility; air pollution; endocrine-disrupting compounds; environmental exposure; semen analysis.