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Periodic Graphics: Sunscreen and coral reef damage

Chemical educator and Compound Interest blogger Andy Brunning reveals how sunscreens damage coral reefs.

by Andy Brunning
July 14, 2019 | APPEARED IN VOLUME 97, ISSUE 28


Andy Brunning
Andy Brunning

To download a pdf of this article, visit

References used to create this graphic:

Impacts of sunscreens on coral reefs

Review of environmental effects of oxybenzone and other sunscreen active ingredients

Sunscreen bans – coral reefs and skin cancer

A collaboration between C&EN and Andy Brunning, author of the popular graphics blog Compound Interest

To see more of Brunning’s work, go to To see all of C&EN’s Periodic Graphics, visit




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Denis Dudley (July 15, 2019 3:44 PM)
Any Polycyclic Aromatic Hydrocarbon (PAH) UV filter like those being banned in Hawaii, Palau, Bonaire, Curacao, Aruba, Key West, and the US Virgin Islands - toxic to coral and the marine habitat are even more dangerous for humans, a fact that seems to get lost in recent news coverage. The FDA has placed virtually all the PAH filters used in typical brand name sunscreens on a “watch” list – insufficient data to support a positive GRASE (Generally Regarded As Safe or Effective) label - safety and efficacy need to be established - to be known as Category III. These include cinoxate, dioxybenzone, ensulizole, homosalate, meradimate, octinoxate, octisalate, octocrylene, padimate O, sulisobenzone, oxybenzone or avobenzone at this time.
I have said for over a decade, just about every day, that most sunscreens are neither SAFE nor EFFECTIVE. My “undesirables” singled out for strict avoidance were avobenzone, oxybenzone, homosalate, octisalate, octocrylene, 4-methyl-benzylidine camphor, and regular (non-encapsulated) octinoxate, present in most brand name, drug store, or doctor dispensed sunscreens. I cautioned that consumers should avoid these soluble Polycyclic Aromatic Hydrocarbon (PAH) sunscreen filters that enter blood and tissue through the skin, and are implicated as hormone disruptors and carcinogens that mutate DNA. Most parents and pregnant women are unaware of these established facts. . In 2008 the Center for Disease Control confirmed that oxybenzone, the most popular UV filter at the time, was found in 96.8 % of Americans, both genders, ages 6-70. Other studies confirmed that 85.2% of nursing mothers had one or more UV filters in breast milk, and 99% of patients having amniocentesis in the 3rd trimester had oxybenzone in amniotic fluid. The golden rule in endocrinology is “isoform function”, same structure - same actions - where permeation and hormone disruption are concerned.
The FDA finally accepts that better methods are needed to confirm the UVA protection afforded by a sunscreen and a BROAD SPECTRUM claim. They also discuss for the first time that many of the PAH filters like oxybenzone may be estrogenic or act as Endocrine Disrupting Chemicals (EDC), which can adversely affect human and wildlife health. They act by hormone disruption of reproductive and other endocrine systems. Benefit Risk Assessment (BRA) is the linchpin of medical management, and a prudent approach to life in general. There are benefits to sun exposure - Vitamin D synthesis, pineal gland stimulation, serotonin and endorphin release which has health benefits and explains why some get immense pleasure from lying in the sun, and nitric oxide production - a benefit in conditions like hypertension and cardiovascular disease. But skin cancer is definitely attributable to sun exposure. Every 54 minutes someone in N. America dies from melanoma - 80% of which is theoretically preventable.
PAH UV filters are mostly UVB except for avobenzone and the products that use them are UVB-BIASED sunscreens that prevent UVB effects like sunburn to varying degrees but offer inadequate protection against the most damaging and deeper penetrating UVA1 rays. UVB is related to the SPF value and the first sunscreens with low SPF protected mostly against UVB radiation (290-320nm). Even today's high SPF sunscreens (SPF 50+) still have little or no UVA1 protection. This incomplete protection could contribute to the rise in annual global skin cancer rates since 1960. The rise parallels the dominance of UVB-BIASED sunscreens that transmit up to 10X more UVA than UVB to your skin, over the same period.
If these sunscreens with poor UVA- attenuation do not prevent cancer - as suggested by a global rise in all forms of skin cancer - the whole Benefit Risk Assessment (BRA) paradigm of sunscreen use takes on a different perspective, where any level of risk, however low, takes on critical significance and may be unacceptable. The FDA is now applying the Precautionary principle in its Feb 2019 proposal. Contemporary studies document widespread effects in human and wildlife from PAH UV filters and their structural analogues like DDT, BPA, and other EDCs. A review of 85 scientific papers in humans and lower species concluded that aromatic hydrocarbon UV filters are generally involved in the disruption of the hypothalamic–pituitary–gonadal system.. More recent studies confirm that UV hydrocarbon filters, and other phenols including the preservative parabens, clearly change levels of virtually every sex hormone, pituitary hormones, thyroid hormones and certain growth factors in both pregnant and non-pregnant women. A change in a hormone level is evidence of HORMONE DISRUPTION. In one of several recent studies in healthy premenopausal women, various phenols, including oxybenzone and parabens changed the levels of key reproductive hormones - FSH (Follicle Stimulating Hormone), (LH) Luteinising Hormone, estradiol, and progesterone. The numerous clinical consequences are another matter, and may not be evident for up to 40 years or more.
Permeation and bioavailability is now an established fact in humans. There appears to be a common pathway for toxicity to humans and the marine eco-system. First PERMEATION then HORMONE DISRUPTION, DNA mutation and genotoxicity. Coral has an epidermis similar to human skin but less complex, and an unintended consequence of human use of PAH UV filters may be the degradation of the marine habitat. The finding of PAH filters in rivers, lakes, remote estuaries, coral reefs, and even in the surface and coastal waters of the Arctic, with further contamination of fish and other marine food sources, should concern all of us. It may also be a secondary route for human contamination.
There is no way to carry out definitive studies on fetal toxicity and identify any mutagenic or epigenetic effects. It is not possible to assess the NOAEL (No Observed Adverse Effect Level) in a fetus. In the situation with PAH UV filters, the BRA equation has only risk to the fetus and no intended benefit. Mineral UV and new insoluble particle type filters can reach the high levels of UVA protection required to prevent skin cancer and photoaging. The future is promising . Properly applied sunscreen can protect the repair p53 and inhibit the cellular basis of all three forms of skin cancer in a landmark Australian study (Hacker et al). The sunscreen likely had at best a modest UVA-PF level and reinforces other studies that modest UVA-PF levels effectively prevented UVR mediated damage. Imagine the possibilities using a modern sunscreen with spectral homeostasis. The uniform reduction of UVB and UVA or “spectral homeostasis" shielding, attenuates the natural spectrum of sunlight without altering its quality, similar to the protection afforded by neutral density filters like densely woven textiles or indoor shade as suggested by Diffey in 1991. This is only possible with efficient UVA filters like zinc oxide, and other synthetic insoluble UVA filters.
Consumers want aesthetic products that spread well. Some mineral products are now transparent and a Former First lady with colored skin apparently uses a 25% pure zinc oxide sunscreen. With education consumers , especially prudent parents, will choose effective sunscreens with little or no risk to humans, coral, marine organisms and the environment in general. If the UV filter is insoluble, of large molecular weight above 500 G/mol or Daltons, it will not permeate human skin and more likely than not to be safe for coral and the marine ecosystem. Safe for humans - safe for coral.

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