Short- and long- term exposures to ambient PM_2.5 and its major constituents in relation to platelet mitochondrial tRNA-Leu methylation among preconception couples

Ambient fine particulate matter (PM_2.5) pose significant global health risks. However, limited evidence exists regarding their potential influence on mitochondrial epigenetic alterations during the preconception period. This cross-sectional observational study aimed to explore the associations between short- and long-term exposures to PM_2.5 and its major constituents including black carbon, organic matter (OM), ammonium, nitrate and sulfate and methylation levels of platelet mitochondrial tRNA-Leu gene. A total of 594 couples preparing for pregnancy in Tianjin, China was included. The methylation levels of tRNA-Leu were detected using pyrosequencing. Multi-variate linear regression and distributed lag linear models were used to evaluate cumulative and lag-specific associations between air pollutants and tRNA-Leu methylation. Our study found significant associations between short-term exposure (7-day average before blood collection) to OM and decreased platelet tRNA-Leu methylation among wives. Long-term exposures (365-day average before blood collection) to PM_2.5 and all its major constituents were also associated with decreased platelet tRNA-Leu methylation in wives. Lag-effect analysis further revealed sex-specific ranges of significant sensitive lag windows. Among wives, significant inverse associations between PM_2.5 and its major constituents and platelet tRNA-Leu methylation were observed over the short-term lag range of 4–6 days, with significant long-term lag range spanning 5–8 months. Among husbands, significant short-term inverse associations were evident over the lag range of 2–3 days, whereas no statistically significant long-term associations were identified. Our findings highlight platelet mitochondrial tRNA-Leu methylation as a potential effect marker for air pollution in preconception couples, emphasizing reducing air pollution exposure during preconception period.