In early 2019, the FDA released a report that reviewed the safety of sunscreen products. Benzophenone-3 (BP-3) and octyl methoxycinnamamte (OMC) two chemical UV filters, active ingredients that absorb rather than reflect UV light, were considered as lacking too much information to have a final decision.

BP-3 has been found to increase birth weight and decrease the length of pregnancy in humans. OMC was found to be genotoxic to liver stem cells and affect the behavior offspring of exposed rats. Both these chemicals have also been classified as endocrine disruptors, compounds that mimic hormones and interfere with the endocrine system. Both BP-3 and OMC have been suggested to act similarly to estrogen, activating estrogen receptors and increasing uterine weight in rats.

Most concerning to human development is that BP-3 and OMC have been found past the placental barrier and have multi-generational effects. BP-3 was found in amniotic fluid, fetal cord blood, and in breast milk, while OMC has been shown to affect offspring of dosed parents, suggesting similar presence past the placental barrier.

This study modeled maternal exposure in Drosophila melanogaster. D. melanogaster were used because they share many developmental pathways with humans, are easy to care for, and have high fecundity. Female D. melanogaster were exposed to concentrations matching, double, and half that of amounts of BP-3 found in human blood, adjusted for the size of D. melanogaster. Additionally, controls of water and acetone were used to control for the acetone BP-3 and OMC were dissolved in. The eggs of dosed females were then collected, imaged, and measured. The size of eggs can be used as a stand in for embryos, egg size corresponds to embryonic development.

This study found that only the low dose (x1/2) of BP-3 and OMC significantly affected the size of D. melanogaster eggs. A decrease in area, major axis length, and minor axis length of eggs was found between control groups and x1/2 concentrations of BP-3. OMC showed similar trends with the low dose (x1/2) being significantly different from the acetone control but not the water control. Large doses (x1 and x2) were found to have no statistical difference from controls.

The significance of low dose effects is reflected in current literature. Endocrine disruptors have long been hypothesized to work at a narrow range of concentrations and have large effects within that range. The results of this study suggest that the upper limit of this range has been found with x1/2 doses, but further research into lower doses should be explored.

Additionally, if the effects that BP-3 and OMC had on D. melanogaster eggs are replicated in humans, the FDA may need to reevaluate its current ruling about safety of UV filters and suggestions concerning sunscreen use during pregnancy.