Reef-safe sunscreen: environmentalconcern or marketing hype?

EURO COSMETICS Magazine • Reef-safe sunscreen: environmentalconcern or marketing hype? • Uli Osterwalder • Uli Osterwalder
Principal and Owner of Sun Protection Facilitator GmbH

In this Sweep the Sun column we discuss the popular sunscreen claims about reef safety Since the bans of some UV filters on some islands or US states, “reef-safe” has become a worldwide claim (Figure 1). Let’s take a closer look at the background of this claim.
A few months ago, we already discussed “Transparency in Cosmetics”. 1 The basis for that was a webinar by the IFSCC. This column is somewhat related to the transparency question and has also been triggered by an IFSCC Webinar debate, that took place this month. 2 The question was: Do you think “reef-safe” sunscreens actually help protect the marine environment? Yes or No? 230 IFSCC members participated in the webinar. The initial poll showed a 43% in favor and 55% opposed to this question.

After the debate between the two experts, the answers changed to 33% Yes and 66% No. So after this hour-long debate and Q&A, apparently fewer people believed in the reef-safe marketing

Before I comment, here is a brief summary of the 10-minute debates between the Yes and the No positions. Perry Romanowski was the moderator, and did an excellent job of introducing the speakers and leading the discussion. According to the IFSCC secretary Mary Lynn Halland, there was probably the liveliest chat board of any of the 81 IFSCC webinars to date, clearly indicating that this is a hot topic.

The two experts in the debate were:
Do you believe that “reef safe” sunscreens genuinely help protect the marine environment?

  • Yes – Point of view: Autumn Blum of Stream2Sea
    (USA, Florida)
  • No – Viewpoint: Dr. Heleen Kibbelaar of Science Meets
    Cosmetics (NL)

Autumn Blum argued mainly from her point of view as a concerned, experienced diver and also sunscreen manufacturer. Both speakers mentioned the pioneer work on the effect of sunscreens
on coral reefs 2008 by Donavan R et al 3 and 2015 by Downs C et al 4.
Dr. Heleen Kibbelaar emphasized the critical reviews of this early work, which concludes that we do not yet know which UV filters are reef safe, in particular we do not know if such filters are organic of inorganic.

EURO COSMETICS Magazine • Reef-safe sunscreen: environmentalconcern or marketing hype? • Uli Osterwalder • Uli Osterwalder
Figure 1: Environmental claims on sunscreens 5
EURO COSMETICS Magazine • Reef-safe sunscreen: environmentalconcern or marketing hype? • Uli Osterwalder • Uli Osterwalder
Figure 2: Most sunscreens claiming “reef-safe” use inorganic sunscreens 5
SUMMARY of YES position
Autumn Blum of Stream2Sea (USA) argued that reef safe sunscreen successfully address a true environmental concern. (
SUMMARY of NO position
Dr. Heleen Kibbelaar of Science Meets Cosmetics (the Netherlands) argued the No-position mainly because we just do not know (yet). (
What is “reef safe”?
•  There is currently no mutually agreed term to define what is reef safe!
•  Brands are creating their own definitions and “Blue Washing” is the new “Green Washing.
•  “Hawaii compliant”, oxybenzone and octinoxate free is used as synony- mous for “reef safe”
•  Consumers are being duped and litigation is beginning
How to be “reef safe”?
•  A mutually agreed standard needs to be created that recognizes what is Reef Safe
•  Preferably do real aquatic toxicity trials prior to bringing to the market
•  Until then, reef safe labeled products should use only non-nano zinc oxide or non-nano titanium dioxide as the active ingredeints.
Use the HEL List as a reference, from Haereticus Environmental Labo- ratory (, Virginia, USA
•  Oxybenzone
•  Octinoxate
•  Butyloctyl Salicilate
•  4-methylbenzylidene camphor
•  Parabens
•  Triclosan
•  Any nanoparticles or “nano-sized” zinc oxide or titanium dioxide
•  Any form of microplastic
Major References
•  2008 Donavan R et al 3
•  2015 Downs C et al 4
•  2020 Wijgerde T et al 6
•  2022 NAS 7
Reef-safe sunscreen:
•  Side note: mineral, chemical UV filters? Why make a difference?
•  jump on the bandwagon?
•  where does this come from?
•  Results: bans in Hawaii, Palau, UC Virgin Islands, Aruba, Bonaire, Key West Florida BP3- EHMC, OCR, 4-MBC
Let’s have a closer look:
•  Carys Mitchelmore 2020 [8] critically reviewed the literature, espe- cially Craig Downs et al 2016 [3]
•  Problems with monitoring data:
–  No analytical QA/QC or appropriate calibration method
– No matrix spikes to check reliability of results (e.g. 80-120% recovery)
– The reported limits of detection (100ng/L) and limits of quantifi- cation (5000 ng/L) are very high for oxybenzone. These are signs of an insensitive method (comparable methods have LoDs of around 1-10 ng/L).
•  Main toxicity issues
–  No analytical monitoring
– No reference toxicant (positive control) to show that the dose- response for the endpoints is robust.
– Collected test organisms from the wild and almost immediately exposed them to treatments in artificial sea water without accli- mation to the test system
– The in vitro tests are not suitable for risk assessment
•  Zinc oxide: “very toxic to aquatic life”?
–  Ingredients with a chronic toxicity below a specific threshold causing toxic effects in the environment
Conclusion (compare also 5).
•  Current situation
–  Several studies implicated UV filters to negatively affect corals
–  Bans on several organic UV filters in different locations
•  A toxicity test (even if it is well performed…)
–  does not equal reef safe
– Environmental risk assessments need to be conducted for both inorganic and organic UV-filters to ensure environmentally safe use
•  “reef-safe” is no official and science-based term
Major References
•  2008 Donavan R et al 3
•  2015 Downs C et al 4
•  2021 Miller et al 5
•  2021 Mitchelmore et al 8
•  2021 Burns et al 9

Here is the abstract by Wijgerde T et al 6, which is a good example of the complexity of the matter. This work shows that effects are species dependent an that temparature has a greater effect than oxybenzone.

Coral bleaching due to global warming currently is the largest threat to coral reefs, which may be exacerbated by altered water quality. Elevated levels of the UV filter oxybenzone in coastal waters as a result of sunscreen use have recently been demonstrated. We studied the effect of chronic oxybenzone exposure and elevated water temperature on coral health. Microcolonies of Stylophora pistillata and Acropora tenuis were cultured in 20 flow-through aquaria, of which 10 were exposed to oxybenzone at a field-rele- vant concentration of ~0.06 μg L−1 at 26 °C. After two weeks, half of the corals experienced a heat wave culminating at 33 °C. All S. pistillata colonies survived the heat wave, although heat reduced growth and zooxanthellae density, irrespective of oxybenzone. Acropora tenuis survival decreased to 0% at 32 °C, and oxy- benzone accelerated mortality. Oxybenzone and heat significantly impacted photosynthetic yield in both species, causing a 5% and 22–33% decrease, respectively. In addition, combined oxy- benzone and temperature stress altered the abundance of five bacterial families in the microbiome of S. pistillata. Our results suggest that oxybenzone adds insult to injury by further weakening corals in the face of global warming.


The two speakers represented their assigned position very well. Autumn Blum reiterated the few early studies 3, 4 and the “HEL List” which contains ingredients that are no longer used (PABA) or have never been used in the US (4-MBC). This HEL list also includes Triclosan (not used in sunscreens), Nano Particles and Microplastic. Besides the blacklisted UV filters Oxybenzone and
Octinoxate, Autumn Blum mentioned “Butyloctyl Salicilate” as an unapproved UV filter found in many sunscreens. Autums presentation introduced me to Tim Wijgerde et al and his study on the effects of oxybenzone, not discounting the temperature effect.
Conclusion that the effect is Species dependent and inferior than the temperature effect 6. Autumn also clearly agreed that ocean warming causes more coral bleaching than UV filteres, but she advocated doing something even if we don’t know everything yet.

Heleen Kibbelaar emphasized that fact that we do not have sufficient knowledge to make decisions about individual UV filters, such as banning them, as has been done in some countries
and US States. Heleen argued that the energy of concern for the environment should go into toxicity testing and risk assessment. The former is a prerequisite for the latter, but not a substitute for risk assessment. This is best illustrated by the example of ZnO, which must be labelled with the aquatic toxicity hazard statement during transport 10. It seems obvious that this does not automatically apply for ZnO in sunscreen, but I have yet to see an official environmental risk assessment (ERA) on this topic. The critical review of Carys Mitchelmore et al 8 discovered inconsistencies in the pioneer works 3, 4 and shows the (scientific) way forward. The need to conduct ERAs was also advocated in the recent report of the (US-) National Academy of Science 7.

On the technical aspect, it may be a good idea to look out beyond sunscreens and cosmetics for methodological help, e.g. in sampling seawater near beaches or coral reefs. Since her critical review on UV filters, we know that Cary Mitchelmore is working in this area 8, 11, but her expertise goes far beyond that and may lead into the realm of oil spill literature where seawater sampling is still being discussed 12, 13.

Conclusion and Summary (Abstract from Miller et al 5)

Toxic effects of UV filters from sunscreens on coral reefs revisited: regulatory aspects for “reef safe” products.

To conclude, the substantial unequal treatment of organic and inorganic UV filters in political decision-making, as well as in the ‘reef safe’ sunscreen market is not scientifically justified leading to regulatory shortcomings in the decisions that have been taken by various states and thus requires adequate revisions. For future regulatory measures, we recommend and highly encourage a risk-based approach for each individual UV filter with equal consideration of both, organic and inorganic UV filters. Thus, the development of an appropriate internationally recognized and standardized ecotoxicological testing protocol for corals is required to allow for a comparable toxicity assessment of UV filters to best protect corals by the use of appropriate sunscreen compositions.

Besides this, the development of sophisticated environmental exposure models based on the application of UV filters in sunscreens is urgently needed in order to allow for a quantitative risk assessment for the marine compartment. In this regard, regulatory requirements need to be put in place, especially for the USA where the number of available UV filters has been limited, despite the lack of a scientifically sound data basis and analysis. Finally, we stress the need to introduce a clear and scientifically sound criteria for the definition of a coral-/reef-safe terminology, besides efforts to reduce the overall influx of sunscreen products into reef environments.

To continue the discussion, possibly in person I recommend two upcoming events in the US and in Europe:

  • 2023 Sunscreen Symposium™, Orlando, FL, Sept. 13 –15 (
  • 16th Sun Protection Conference, London, UK, Nov. 28/29 ( In addition to Florida and London, the Cosmetic Science Conference (CSC) will also be held at SEPAWA in between, October 25–26, 2023. We’ll see what this very busy fall brings us.


  1. Osterwalder Uli, Do we need more transparency in Sun Protection?, Sweep the Sun, EURO-COSMETICS Newsletter, 2 023-04-25,
  2. IFSCC Webinar, 9th August 2023
  3. Danovaro R, Bongiorni L, Corinaldesi C, Giovannelli D, Damiani E, Astolfi P, et al. Sunscreens cause coral bleaching,by promoting viral infections. EnvironHealth Perspect. 2008;116(4):441–7, doi: 10.1289/ehp.10966.
  4. Downs CA, Kramarsky-Winter E, Segal,R, Fauth J, Knutson S, Bronstein O, et al. Toxicopathological effects of the sunscreen UV filter, oxybenzone (benzophenone-3), on coral planulae and cultured primary cells and its environmental contamination in Hawaii and the U.S. Virgin Islands. Arch Environ Contam Toxicol. 2016;70:265–88. doi: 10.1007/s00244-015-0227-7.
  5. Miller, I.B., Pawlowski, S., Kellermann, M.Y. et al. Toxic effects of UV filters from sunscreens on coral reefs revisited: regulatory aspects for “reefsafe” products. Environ Sci Eur 33, 74 (2021).
  6. Wijgerde T, van Ballegooijen M, Nijland R, van der Loos L, Kwadijk C, Osinga R, Murk A, Slijkerman D. Adding insult to injury: Effects of chronic oxybenzone exposure and elevated temperature on two reef-building corals. Sci Total Environ. 2020 Sep 1;733:139030. doi: 10.1016/j.scitotenv. 2020.139030. Epub 2020 May 4. PMID: 32446051.
  7. National Academy of Science (NAS) Review of Fate, Exposure, and Effects of Sunscreens in Aquatic Environments and Implications for Sunscreen Usage and Human Health, Washington (DC): National Academies Press (US); 2022 Aug 9. Available from: 10.17226/26381
  8. Mitchelmore CL, Burns EE, Conway A, Heyes A, Davies IA. A Critical Review of Organic Ultraviolet Filter Exposure, Hazard, and Risk to Corals. Environ Toxicol Chem. 2021 Apr;40(4):967-988. doi: 10.1002/etc.4948. Epub 2021 Feb 2. PMID: 33528837; PMCID: PMC8048829.
  9. Burns EE, Csiszar SA, Roush KS, Davies IA, National scale down-thedrain environmental risk assessment of oxybenzone in the United States, Integrated Environmental Assessment and Management – Volume 17, Number 5 – pp. 951– 96, DOI: 10.1002/ieam.4430
  11. Conway AJ, Gonsior M, Clark C, Heyes A, Mitchelmore CL. Acute toxicity of the UV filter oxybenzone to the coral Galaxea fascicularis. Sci Total Environ. 2021 Nov 20;796:148666. doi: 10.1016/j.scitotenv.2021.148666. Epub 2021 Jun 25. PMID: 34273823.
  12. Takeshita R, Bursian SJ, Colegrove KM, Collier TK, Deak K, Dean KM, De Guise S, DiPinto LM, Elferink CJ, Esbaugh AJ, Griffitt RJ, Grosell M, Harr KE, Incardona JP, Kwok RK, Lipton J, Mitchelmore CL, Morris JM, Peters ES, Roberts AP, Rowles TK, Rusiecki JA, Schwacke LH, Smith CR, Wetzel DL, Ziccardi MH, Hall AJ. A review of the toxicology of oil in vertebrates:what we have learned following the Deepwater Horizon oil spill. J Toxicol Environ Health B Crit Rev. 2021 Nov 17;24(8):355-394. doi: 10.1080/10937404.2021.1975182. Epub 2021 Sep 19. PMID: 34542016.
  13. Parkerton T, Boufadel M, Nordtug T, Mitchelmore C, Colvin K, Wetzel D, Barron MG, Bragin GE, de Jourdan B, Loughery J. Recommendations for advancing media preparation methods used to assess aquatic hazards of oils and spill response agents. Aquat Toxicol. 2023 Jun;259:106518. doi: 10.1016/j.aquatox.2023.106518. Epub 2023 Apr 3. PMID: 37030101.
EURO COSMETICS Magazine • Uli Osterwalder • Uli Osterwalder • Uli Osterwalder
Uli Osterwalder

Uli Osterwalder studied Chemical Engineering at ETH Zurich, Switzerland and at the University of Houston in Houston, Texas. He joined Ciba-Geigy in Basel in 1979 where he first developed a Phosgene Generator in central process development. Later he developed his leadership skills in Project Management and Process Analytics. At Ciba Specialty Chemicals Uli Osterwalder helped establish new business development in Fabric Care and Personal Care. After the acquisition by BASF SE he became Senior Marketing Manager and Scientific Adviser in Sun Care in Ludwigshafen and Duesseldorf.
2016 he came back to Basel, working for DSM as senior Senior Scientific Adviser suncare for two years. 2018 he started his own company, Sun Protection Facilitator GmbH and is committed to contribute to further improvements in sun protection. Uli Osterwalder works for ISO on the development of new UV protection assessment methods and is now chairing the technical committee ISO TC/217 (Cosmetics). He is author and co-author of numerous scientific articles and book chapters on sun protection.

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