Ambient air pollution and inflammation-related proteins during early childhood

Background and aim: Experimental studies show that short-term exposure to air pollution may alter cytokine concentrations. There is, however, a lack of epidemiological studies evaluating the association between long-term air pollution exposure and inflammation-related proteins in young children. Our objective was to examine whether air pollution exposure is associated with inflammation-related proteins during the first 2 years of life.

Methods: In a pooled analysis of two birth cohorts from Stockholm County (n = 158), plasma levels of 92 systemic inflammation-related proteins were measured by Olink Proseek Multiplex Inflammation panel at 6 months, 1 year and 2 years of age. Time-weighted average exposure to particles with an aerodynamic diameter of <10 μm (PM₁₀), <2.5 μm (PM_2.5), and nitrogen dioxide (NO₂) at residential addresses from birth and onwards was estimated via validated dispersion models. Stratified by sex, longitudinal cross-referenced mixed effect models were applied to estimate the overall effect of preceding air pollution exposure on combined protein levels, "inflammatory proteome", over the first 2 years of life, followed by cross-sectional protein-specific bootstrapped quantile regression analysis.

Results: We identified significant longitudinal associations of inflammatory proteome during the first 2 years of life with preceding PM_2.5 exposure, while consistent associations with PM₁₀ and NO₂ across ages were only observed among girls. Subsequent protein-specific analyses revealed significant associations of PM₁₀ exposure with an increase in IFN-gamma and IL-12B in boys, and a decrease in IL-8 in girls at different percentiles of proteins levels, at age 6 months. Several inflammation-related proteins were also significantly associated with preceding PM₁₀, PM_2.5 and NO₂ exposures, at ages 1 and 2 years, in a sex-specific manner.

Conclusions: Ambient air pollution exposure influences inflammation-related protein levels already during early childhood. Our results also suggest age- and sex-specific differences in the impact of air pollution on children's inflammatory profiles.