Impacts of sunscreens on coral reefs
Composition of sunscreens Active ingredients. UV filters Absorb, reflect or scatter UV light a) Organic (chemical) b) Inorganic (mineral) Inactive ingredients. Antimicrobial preservatives, moisturisers and antioxidants Typically 50-70% of product Ingredients of a typical sunscreen
Occurrence in environment Sunscreen pollution from recreation: 4,000-16,000 tons estimated to wash off people into coral reef areas annually. Pollution from wastewater treatment effluents: UV filters from sunscreens and other personal care products are contaminants of wastewater which subsequently may reach coastal waters. There is growing concern that some UV filters may be having a negative impact on corals and other reef biota. Some of the concentrations found in sea water are considered to be environmentally relevant and to pose a threat to reefs.
Concentrations in environment Seawater analysis from sites around world shows variable levels e.g. from barely detectable - 0.4 parts per trillion (ppt) oxybenzone (BP-3) at Okinawa, Japan to 1.395 parts per million (ppm) BP-3 (US Virgin Islands) Concentration of BP-3 in the water column at two sites in Trunk Bay US Virgin Islands. From Downs et al., 2015
Reported impacts Bleaching of hard corals exposed to benzophenone (BP-2 and BP-3), shown in controlled experiments with coral nubbins Effect of 100-µL sunscreens on Acropora nubbins after 24-hr incubation A ) control; ( B ) nubbins incubated at 28 C; and ( C ) nubbins incubated at 30 C. Danovaro et al., 2008 (note bleaching exacerbated by increased temp). In the dark: bleaching results from the symbiophagy of zooxanthellae; host cells eat the zooxanthellae (Downs et al. 2009). In the light: BP-2 causes direct damage to zooxanthellae, independent of any hostregulated degradation mechanism.
Reported impacts Damage and deformation of coral larvae (planulae) Lab experiments (Downs et al., 2016) Planula exposed to BP-3 for 8 h in light A. Control: normal shape: zooxanthellae organised into rows B. Planula exposed to 22.8 parts per billion (µg/l) BP-3 became deformed. C. Planula exposed to 228 parts per billion (µg/l) BP-3. Deformed and loss of zooxanthellae Damage to coral DNA and reproductive success
Implications: risk assessment Preliminary risk assessment in Hong Kong indicated over 20% of coral samples contained oxybenzone (BP-3) concentrations exceeding the threshold values for causing larval deformities and mortality in the worst-case scenario. Tsui et al., 2017. Detection frequency of BP-3 was >65% in coral tissues; concentrations up to 31.8 ng/g wet wt. Higher probabilities of negative impacts of BP-3 on coral communities are predicted to occur in wet season.
Next steps More research is needed to better understand the sunscreen issue, BUT Considering the many stresses already faced by reefs and the current concerns about the toxicity of certain components of sunscreens to corals. A proactive and precautionary approach is recommended, especially in areas with high levels of marine-based tourism.
Further research Monitor concentrations of sunscreen components in seawater, sediment & biota at remote v populated areas. Widen studies to investigate impacts of sunscreen pollution at reef community and/or ecosystem level. Study effects of pharmaceutical and personal care products (PPCPs) mixtures in addition to single components. Identify organismal or subcellular/cellular-level biomarkers that indicate sunscreen pollution effects. Investigate extent and significance of bio-concentration and bio-accumulation of organic UV filters. Determine which ingredients are safe and which pose a realistic threat to marine ecosystems
Practical steps Action to minimise impacts: Encourage manufacture and use of reef-friendly sunscreens. Encourage other methods of UV protection. Guidance already exists collective action and focussed campaigns could lead to reduction in sunscreen pollution.
Other actions Ban/regulate sale/use of sunscreens containing toxins. Mexico eco-marine parks only allow reef friendly sunscreen Hawai i is seeking a legislative ban on sunscreens containing oxybenzone. Exert consumer pressure on industry practice. Support financial disincentives to decrease price of reeffriendly sunscreens