Conventional Sunscreens: UV Filters & Research

Scientific data on conventional chemical (organic) sunscreen ingredients, their UV protection mechanisms, systemic absorption, and safety concerns from peer-reviewed research

Conventional Sunscreens Overview

Chemical (organic) UV filters work by absorbing UV radiation and converting it into heat energy. These carbon-based compounds are designed to absorb specific wavelengths of UV light, with different filters targeting UVA, UVB, or both.

Systemic absorption concerns have emerged from recent FDA studies. Research shows that six common chemical filters—avobenzone, oxybenzone, octocrylene, homosalate, octisalate, and octinoxate—are absorbed through the skin at levels exceeding FDA safety thresholds after just one application.

Regulatory status varies globally. While the FDA has requested additional safety data for 12 chemical filters, the EU has banned or restricted several ingredients. Hawaii and Key West have banned oxybenzone and octinoxate due to coral reef toxicity concerns.

Chemical Filter Categories

Chemical sunscreens are grouped into families based on their molecular structure:

• Cinnamates: Primarily UVB filters including octinoxate (most common in US)
• Benzophenones: Broad-spectrum filters like oxybenzone (highest absorption rates)
• Salicylates: Weak UVB absorbers used in high concentrations (homosalate, octisalate)
• PABA derivatives: Potent UVB filters, largely phased out due to allergic reactions
• Dibenzoylmethanes: UVA filters like avobenzone (requires stabilization)

Systemic Absorption Research

FDA absorption studies (2019-2020) found that chemical sunscreen ingredients are absorbed at levels far exceeding the agency's safety threshold of 0.5 ng/mL:

Key findings include:

• Avobenzone detected at 9 times the FDA cutoff
• Octisalate absorbed at 10 times the safety threshold
• Homosalate and oxybenzone detected three weeks after application
• All tested ingredients exceeded safety thresholds after single use

Photostability Challenges

Many chemical filters degrade when exposed to UV light, reducing their effectiveness:

• Avobenzone: Degrades by 50% after 1 hour without stabilizers
• Octinoxate: Not photostable, breaks down rapidly in sunlight
• Oxybenzone: Photodegradation concerns, requires stabilization

To address this, formulations combine photostabilizers like octocrylene with unstable filters, though this increases the chemical load absorbed by skin.

Safety Concerns

Endocrine disruption is a primary concern with several chemical filters. Studies have found:

• Oxybenzone associated with lower testosterone in adolescent boys
• Octinoxate and other filters showed estrogenic activity in animal studies
• Homosalate restricted in EU due to hormone disruption concerns
• Multiple filters detected in breast milk and urine samples

Environmental impact has led to regional bans:

• Hawaii banned oxybenzone and octinoxate to protect coral reefs (2021)
• Key West followed with similar legislation
• Studies show these chemicals contribute to coral bleaching at very low concentrations

FDA Position and Proposed Rule

In 2021, the FDA proposed that only zinc oxide and titanium dioxide be classified as GRASE (Generally Recognized As Safe and Effective). For chemical filters, the agency determined:

• Not GRASE due to safety concerns: Aminobenzoic acid (PABA) and trolamine salicylate
• Insufficient data for GRASE determination: 12 filters including avobenzone, oxybenzone, octinoxate, homosalate, octisalate, and octocrylene

Recommendations

Based on current research, individuals concerned about chemical absorption may consider:

• Mineral sunscreens with zinc oxide and/or titanium dioxide
• Protective clothing and shade as primary sun protection
• If using chemical sunscreens, choosing newer photostable formulations
• Avoiding spray formulations that increase inhalation risk

Individual Chemical Sunscreen Research Pages

Explore detailed research on each chemical UV filter's properties, safety studies, and regulatory status: