Sun Bum does not claim its sunscreens are biodegradable. The brand markets its products as “Hawaii Act 104 Compliant,” meaning they’re made without oxybenzone and octinoxate, but that’s a reef-safety claim, not a biodegradability claim. Whether the formulas actually break down in the environment depends on which Sun Bum product you’re using and what’s in it.
What Sun Bum Actually Claims
Sun Bum’s environmental messaging centers on one thing: compliance with Hawaii’s Act 104, which bans sunscreens containing oxybenzone and octinoxate from sale in Hawaii due to their documented harm to coral reefs. All Sun Bum sunscreens sold in the U.S. are free of both ingredients. The brand is careful to note that there’s no agreed-upon testing protocol for terms like “reef safe” or “biodegradable” when it comes to sunscreen, and those claims aren’t regulated by the FDA. So Sun Bum sticks to referencing the Hawaii law rather than making broader environmental promises.
This is an important distinction. “Reef compliant” means two specific chemicals were left out. It doesn’t mean the remaining ingredients break down quickly in water, soil, or marine environments.
The Original Line: Chemical Filters That Persist
Sun Bum’s Original sunscreen line (their most popular products) uses chemical UV filters including avobenzone, homosalate, octisalate, and octocrylene. These are the active ingredients that absorb UV radiation before it reaches your skin. From an environmental standpoint, their biodegradability varies, and the picture isn’t great.
Octocrylene is one of the more persistent UV filters studied in freshwater environments. Research published in Science of the Total Environment measured environmental half-lives for common UV filters under natural light and found that octocrylene showed no significant loss over 144 hours (six full days) in water. Its fate in the environment appears to be driven mainly by physical dispersion rather than chemical breakdown. The Environmental Working Group flags octocrylene for persistence, bioaccumulation, and cellular-level changes.
Homosalate and octisalate raise their own concerns. EWG rates homosalate for potential endocrine disruption and enhanced skin absorption, while octisalate carries similar flags. Neither is among the UV filters that degrade quickly in aquatic settings. Avobenzone, the fourth active ingredient, carries contamination concerns from its breakdown products, though it tends to be less persistent than octocrylene.
None of these chemical filters would meet a strict definition of “biodegradable” in the way most people understand the word.
The Mineral Line: A Different Formula
Sun Bum also makes a Mineral sunscreen line that uses zinc oxide (20%) as its only active ingredient. Zinc oxide is an inorganic mineral, so it doesn’t biodegrade in the traditional sense. Instead, it stays in its mineral form. It doesn’t accumulate in living tissue the way some chemical filters do, and it isn’t associated with the same coral toxicity concerns as oxybenzone or octocrylene.
The inactive ingredients in the mineral formula lean more natural: coconut oil, shea butter, cocoa seed butter, and plant-derived emulsifiers like coco glucoside. Many of these would break down relatively easily in the environment. The formula does contain phenoxyethanol (a synthetic preservative) and several specialty emollients, but the overall ingredient profile is simpler and more likely to degrade than the chemical version.
If your primary concern is environmental breakdown, the Mineral line is the better choice within the Sun Bum range, though the brand still doesn’t label it as biodegradable.
Why “Reef Safe” and “Biodegradable” Aren’t the Same
These two terms get conflated constantly in sunscreen marketing, but they describe completely different things. Reef safety typically refers to whether a sunscreen contains chemicals known to damage coral, particularly oxybenzone and octinoxate. Biodegradability refers to whether the formula’s ingredients break down into harmless substances over time through natural processes like microbial activity or sunlight.
A sunscreen can be reef compliant and still contain ingredients that persist in waterways for days or weeks. Sun Bum’s Original line is a good example: it meets Hawaii’s reef law but contains octocrylene, which resists breakdown in freshwater. Conversely, a product could theoretically biodegrade quickly but still contain compounds that stress marine life during the hours before it breaks down.
How UV Filters Behave in Water
When you swim wearing sunscreen, a portion washes off into the surrounding water. What happens next depends on the specific chemicals involved. Some UV filters degrade through photolysis, meaning sunlight breaks them apart. Others resist both sunlight and microbial breakdown, lingering in water or settling into sediment.
The freshwater study that tested ten common UV filters found a wide range of outcomes. Some compounds broke down within hours. Octinoxate (which Sun Bum excludes) had a half-life of about 23 hours. But octocrylene and three other filters showed zero measurable loss after six days of monitoring. For those persistent chemicals, environmental concentrations are primarily reduced by dilution and physical dispersal rather than actual degradation.
This matters most in enclosed or slow-moving bodies of water like lakes, bays, and reef lagoons, where dilution is limited and sunscreen chemicals can accumulate to measurable concentrations during peak swimming season.
Choosing a Lower-Impact Option
If you’re specifically looking for a sunscreen that breaks down in the environment, you’ll want to look beyond Sun Bum’s marketing language and check the active ingredients on the label. Within the Sun Bum lineup, the Mineral products (zinc oxide only) have the smallest environmental footprint. They skip the persistent chemical filters entirely and rely on ingredients that are either inert minerals or naturally derived compounds.
For any sunscreen brand, a few practical guidelines reduce your environmental impact. Mineral-only formulas with zinc oxide or titanium dioxide avoid the most persistent synthetic UV filters. Simpler ingredient lists with fewer specialty chemicals mean fewer unknowns in terms of aquatic toxicity. And applying sunscreen 15 to 20 minutes before swimming gives it time to bind to your skin, reducing the amount that washes off immediately.
No sunscreen is completely neutral once it enters a body of water. But the gap between a zinc oxide formula with plant-based emollients and a chemical formula loaded with octocrylene is significant enough to matter if environmental impact is part of your buying decision.