Estimating the Risk of Women Anemia Associated with Ozone Exposure Across 123 Low- and Middle-Income Countries: A Multicenter Epidemiological Study

Anemia in women of reproductive age (WRA) presents a pressing global public health issue, particularly in low- and middle-income countries (LMICs). Yet, the potential impact of ozone (O₃) exposure on anemia remains uncertain. The study included 1,467,887 eligible women from 83 surveys of 45 LMICs between 2004 to 2020. Monthly O₃ exposure was estimated using machine learning, with the year preceding the survey as the primary exposure window. Fixed-effects models evaluated the association between O₃ and anemia. An exposure-response function (ERF) was constructed using a varying-coefficient regression model, and then extrapolated to estimate the anemia burden in relation to O₃ in 123 LMICs. In the fully adjusted regression model, each 10 ppb increase in annual O₃ concentration was associated with an 8% elevation in anemia risk. The nonlinear ERF indicated a threshold effect of O₃ on anemia at approximately 47.2 ppb. In 2020, more than 7.6 million anemic WRA (1.58%) in 123 LMICs were associated with O₃ exposure. The potentially attributable burden has generally decreased from 2004 to 2020, notably in South Asia. Our findings highlight the importance of air pollution mitigation in LMICs to address anemia disparities among women.