The influence of fine particulate matter on the association between residential greenness and ovarian reserve

Natural vegetation, or greenness, is thought to improve health through its ability to buffer and reduce harmful environmental exposures as well as relieve stress, promote physical activity, restore attention, and increase social cohesion. In concert, these effects could help mitigate the detrimental effects of air pollution on reproductive aging in women. Our analysis included 565 women attending the Massachusetts General Hospital Fertility Center (2004–2014) who had a measured antral follicle count (AFC), a marker of ovarian reserve. We calculated peak residential greenness in the year prior to AFC using 250 m² normalized difference vegetation index (NDVI) from the Terra and Aqua satellites operated by the United States National Aeronautics and Space Administration. Validated spatiotemporal models estimated daily residential exposure to particulate matter <2.5 μm (PM₂.₅) for the 3 months prior to AFC. Poisson regression models with robust standard errors were used to estimate the association between peak greenness, average PM₂.₅ exposure, and AFC adjusted for age, BMI, smoking status, education, year, and season. Women in our study had a mean age of 35.2 years with a standard deviation (SD) of 4.3 years (min: 20 years, max: 45 years). The peak residential NDVI ranged from 0.07 to 0.92 with a SD of 0.18. There was no statistically significant association between peak residential greenness and AFC; however, higher exposure to PM₂.₅ was associated with lower AFC (−6.2% per 2 μg/m³ [1 SD increase] 95% CI -11.8, −0.3). There was a significant interaction between exposure to PM₂.₅ and peak greenness on AFC (P-interaction: 0.03). Among women with an average PM₂.₅ exposure of 7 μg/m³, a SD increase in residential peak greenness was associated with a 5.6% (95% CI -0.4, 12.0) higher AFC. Conversely, among women with a PM₂.₅ exposure of 12 μg/m³, a SD increase in residential peak greenness was associated with a 5.8% (95% CI -13.1, 2.1) lower AFC. Residing in an area with high levels of greenness may slow reproductive aging in women only when exposure to PM₂.₅ is low.