الفجوة في حماية UVA تكشف لماذا تحتاج إلى مضادات الشمس الجديدة

UVA rays, which standard SPF ignores, can raise skin cancer risk, yet U.S. sunscreens lack a UVA‑PF metric.

How Sunscreen Works

Sunscreens block or absorb ultraviolet light. Mineral formulas use zinc oxide or titanium dioxide nanoparticles that act as tiny mirrors, reflecting UVB (280‑315 nm) and UVA (315‑400 nm). Chemical sunscreens contain molecules like avobenzone, ecamsule, octocrylene, and oxybenzone that absorb UV wavelengths and dissipate the energy as heat. The Sun Protection Factor (SPF) rating, set by the FDA, measures only UVB protection; a product labeled “broad spectrum” is supposed to cover UVA, but no U.S. metric quantifies that coverage.

Regulatory Gaps and Safety Concerns

Because SPF does not account for UVA, consumers may believe they are fully protected while still receiving harmful UVA exposure. In 2019 the FDA released a study showing that some chemical ingredients can enter the bloodstream, prompting calls for more data. Meanwhile, spray‑on sunscreens have been recalled for benzene contamination, and several UVA‑absorbing molecules are linked to coral reef damage.

Next‑Gen Formulations

Researchers like AJ Addae at UCLA are engineering zinc oxide particles with altered shapes to reduce the white cast while maintaining UV reflection. Kerry Hanson at UC Riverside notes that transparent chemical sunscreens can be formulated to absorb UVA without leaving a sheen. These advances could soon give consumers a single, transparent sunscreen that shields against both UVB and UVA without the white cast.

Source: Experts explain how sunscreen really works-and why better ones may be coming soon
Domain: scientificamerican.com