A large cohort study found that pregnant women living in U.S. counties with higher radon levels had a significantly greater risk of developing gestational diabetes compared with those in areas with lower exposure.

The study, published in JAMA Network Open, analyzed data from 9,107 nulliparous pregnant participants across eight U.S. clinical centers. Individuals residing in counties with radon levels ≥ 2 pCi/L had a 37% higher risk of gestational diabetes (GD) compared with those in areas with < 1 pCi/L (odds ratio [OR] = 1.37, 95% confidence interval [CI] = 1.02–1.84). These findings remained consistent after adjusting for fine particulate matter (PM2.5) exposure (OR = 1.36, 95% CI = 1.00–1.86). Overall, 382 participants (4.2%) were diagnosed with GD.

Sensitivity analyses were conducted to assess the robustness of the findings. These included imputing missing radon or GD data and assigning participants with missing data to either high- or low-radon groups. The results remained unchanged, further supporting the study's conclusions.

While subgroup analyses revealed that ever-smokers in high-radon counties had more than double the risk of developing GD (OR = 2.09, 95% CI = 1.41–3.11), no statistically significant interactions between radon and smoking or radon and PM2.5 were detected on either additive or multiplicative scales. Participants exposed to both high radon and high PM2.5 levels also exhibited an elevated risk of GD (OR = 1.93, 95% CI = 1.31–2.83).

The study built upon earlier research linking ambient particle radioactivity to GD. A previous Massachusetts study identified a similar association with GD after controlling for PM2.5. However, the current study is the first to comprehensively evaluate radon exposure—encompassing both gaseous and attached forms—and its link to GD.

“This is the first study to examine the association between radon exposure and the risk of GD,” the study authors wrote. They proposed that radon’s alpha particle emissions could induce oxidative stress and promote inflammation, processes implicated in GD and other chronic conditions.

While the findings suggested a significant association between radon exposure and GD risk, the investigators cautioned that causality cannot be inferred from their study. They emphasized the need for future research incorporating individual-level indoor radon exposure data to validate the results and further explore biological mechanisms.

The research utilized county-level radon data from the Lawrence Berkeley National Laboratory and was supported by grants from the National Institutes of Health. Data were drawn from the Nulliparous Pregnancy Outcomes Study: Monitoring Mothers-to-Be (nuMoM2b) cohort, collected between October 2010 and September 2013.

Conflict of interest disclosures can be found in the study.