Environment/Climate Change
Residential radon exposure and birth weight Meghan Angley* Meghan Angley Yijia Zhang Uma Reddy Ka Kahe
Objective: Radon is the major source of background radiation exposure in the U.S. Only one other study has examined residential radon and birth weight, despite the fact that ionizing radiation exposure during pregnancy is known to cause fetal growth restriction.
Methods: We used data from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-To-Be (nuMoM2b), a multi-center prospective cohort study of women. Estimates of residential radon exposure in pCi/L at the county level were developed by the Lawrence Berkeley National Laboratory and linked to participants by maternal address. Birth weight (BW) was collected via chart abstraction. BW was converted to z-scores for gestational age and infant sex using the INTERGROWTH-21st standards. Linear mixed models included random effects for study center and adjusted for maternal age, BMI, smoking, education, percent of the federal poverty level, season of conception and average PM2.5 levels during pregnancy. We also examined interaction by maternal smoking status in the 3 months prior to pregnancy.
Results: We excluded participants whose pregnancies ended prior to 20 weeks gestation and implausible birth weight values. Of the 6,278 women with non-missing data included in the analysis, the median county-level radon concentration was 1.6 pCi/L (IQR: 0.9-2.8). After adjustment for confounders, radon was not associated with BW z-scores (-0.02 [95% CI: -0.05, 0.02]). However, radon was associated with lower BW z-scores among women who smoked ≥20 cigarettes/day (-0.16 [95% CI: -0.33, 0.01] and those who smoked 0 – <20 cigarettes/day (-0.06 [95% CI: -0.13, 0.01]), but not those who did not smoke prior to pregnancy (0.00 [95% CI: -0.04, 0.03]).
Conclusions: Radon was found to be associated with lower birthweight among women who smoked prior to pregnancy. Next steps include obtaining radon measurements at a more granular level and examining how residential radon exposure affects trajectories of fetal growth.