Sunscreens.

Nano-sized inorganic UV filters in sunscreens can be absorbed through skin and may have endocrine-disrupting effects—concerns that are especially relevant for damaged skin and children. The good news: sunscreens still significantly prevent skin aging, actinic keratoses, and squamous cell carcinomas when used properly, though melanoma and basal cell carcinoma prevention remains unproven. Thinner applications (under 1.5 mg/cm²)—closer to what people actually use—pose lower safety risks than the recommended 2 mg/cm² dose.