Exposure to Particulate Matter (PM) During Pregnancy and Non-Hodgkin Lymphomas in Children

Background/Objectives: Lymphomas are the third most common pediatric malignancy, with non-Hodgkin lymphoma (NHL) comprising around 7% of childhood cancers. Environmental exposures have been linked to its etiology. Particulate matter (PM) prenatal exposure is increasingly scrutinized for potential effects on early-life carcinogenesis. We investigated whether exposure during pregnancy to PM_2.5 and PM₁₀ was associated with childhood NHL incidence. Methods: A population-based case-control study was conducted in Spain (2009-2016), including 3,682,038 children < 15 years. Incident NHL cases (n = 289) were identified through the Spanish Childhood Tumor Registry. Prenatal PM_2.5 and PM₁₀ exposures were estimated using a random forest model. Logistic regression estimated odds ratios (ORs) and 95% confidence intervals (CIs). Exposures were modeled continuously and categorically by tertiles (low, medium, or high exposure) to assess nonlinearity; trimester-specific analyses were also explored. Results: In the analysis with the continuous exposure, higher prenatal PM_2.5 was associated with increased odds of NHL, and PM₁₀ showed smaller associations. With categorical variables, medium and high-level exposure to PM_2.5 showed an association with higher NHL incidence, especially in the third trimester. High-level exposure to PM₁₀ during the first and second trimesters was linked to a higher NHL incidence in children under five years. Conclusions: Maternal PM_2.5 and PM₁₀ exposure during pregnancy could be associated with childhood NHL incidence, with stronger associations among children diagnosed before age 5. These findings warrant replication and mechanistic investigation.