Background: Studies have shown that higher solar UV radiation exposure (UVR) may be related to lower risk of some cancers in adults. Recently, an ecologic study reported lower risks of some cancers among children living in higher UVR cities and countries. In a large population-based case-control study in California, we tested the hypothesis that childhood cancers may be influenced by UVR.
Methods: Cancers in children ages 0 to 5 years were identified from California Cancer Registry records for 1988 to 2007 and linked to birth certificate data. Controls were sampled from the birth certificates at a ratio of 20:1. Based on birth address, we assigned UVR exposure in units of Watt-hours/m(2) using a geostatistical exposure model developed with data from the National Solar Radiation Database.
Results: For cases with UVR exposure of 5,111 Watt-hours/m(2) or above, we estimated a reduction in odds of developing acute lymphoblastic leukemia (OR: 0.89, 95% CI: 0.81-0.99), hepatoblastoma (OR: 0.69, 95% CI: 0.48-1.00), and non-Hodgkin's lymphoma (OR: 0.71, 95% CI: 0.50-1.02) adjusting for mother's age, mother's race, and child's year of birth. We also observed a small increase in odds for intracranial/intraspinal embryonal tumors (OR: 1.29, 95% CI: 1.01-1.65).
Conclusions: Our findings suggest that UVR during pregnancy may decrease the odds of some childhood cancers. Future studies should explore additional factors that may be correlated with UVR exposure and possibly include biomarkers of immune function and vitamin D.
Impact: This study shows protective associations of UVR with some childhood cancers.