Fish Facts

Fish Facts: Slip, slop, and a slap in the face for aquatic environments

Coral friendly sunscreen may be part of the solution 

SKIN cancer is Australia’s most common form of cancer, but regular use of sunscreens has been proven to reduce the risk of developing melanomas and other forms of skin cancers like basal cell carcinomas. Fishers spend more time out in the environment than most, and there is no doubt that using sunscreens is an important for your health and wellbeing on the water. However, new research is showing that the nanotechnology used in todays sunscreens that makes them so effective and easy to use, has a toxic downside for the organisms living in aquatic environments.

Skin cancer is caused by damage to the skin cells arising from exposure to UV radiation. Sunscreens work by blocking or reflecting the UV radiation before it can damage the skin. However, the fact that some of the chemicals used in sunscreens to block UV can damage corals has been known for some time. In 2008 researchers from Italy found[1] that UV-disrupting chemicals in sunscreens caused coral bleaching by inducing viral infections in the symbiotic algae (zooxanthellae) that are required for growth and survival of hard corals. The researchers found this effect occurred even at very low concentrations, leading them to conclude that sunscreens leaching into the water probably contributed to coral bleaching in many coral reefs with high levels of recreational in-water use (e.g. swimming, diving). Indeed, they calculated that between 16,000 and 25,000 tonness of sunscreen is used each year in tropical countries, and that at least 25% of that is washed off during swimming, accounting for release of 4,000–6,000 tonnes/year in coral reef areas, potentially threatening up to 10% of the worlds coral reefs.

The conclusions from this initial research were met with scepticism by some members of the scientific community, but it seems these results are repeatable – recent research published this year has confirmed that environmental concentrations of a UV blocker (oxybenzone) used in some sunscreens caused fatal deformities in larval corals, posing a hazard to coral reef conservation[2]. But what is even more worrying is that it seems not only corals are threatened by sunscreens.

Nanoparticles of titanium dioxide and zinc oxide have been used in sunscreens for some years now as the primary method for blocking or reflecting UV light. Nanoparticles are classed as particles smaller than 100 nanometres (a nanometre is 0.000001 millimetre, and is invisible to the human eye). Sunscreens that use nanoparticles thus appear to be invisible once applied, unlike the older zinc creams which contain much larger zinc particles that give them an opaque appearance. In contrast to good old zinc cream, sunscreens containing transparent nanoscale titanium dioxides are easier to apply and are still highly protective against UV radiation. Consumer safety groups generally agree that nanoparticles of titanium dioxide used at concentrations up to 25% as UV filters in sunscreens are considered safe for external use on humans. But what are their effects on other animals ?

Unfortunately, the data doesn’t look good. In today’s world its widely recognised that our estuaries and coastal waters are where a large proportion of nanoparticles used in sunscreens, cosmetics and other industrial uses (in chemicals, paints, and dyes) end up mainly via the sewerage and stormwater networks. Unfortunately, research has shown that nanoparticles are extremely persistent in the environment and they tend to be aggregated into biological systems via various pathways. Filter feeding organisms are right in the firing line and it has been found that even extremely low concentrations of titanium dioxide (and other metallic nanoparticles) can be accumulated and become toxic to key estuarine species such as oysters, mussels and other bivalves. Toxicity, reduced survival or delayed development in delicate larvae and reduction in immune responses, disruption of digestion and reproduction and various other impacts on juvenile and adult bivalves have been documented. Even more worrying is research that shows chronic exposure of several generations of planktonic crustaceans to titanium dioxide nanoparticles can cause population collapses. Because zooplankton and filter feeding bivalves are a critical parts of the bottom end of the food chain, (and are also important food items for most species of fish of interest to anglers), these sorts of insidious impacts should be of concern.

Well, now we know the potential problems with sunscreens, what can anglers do to reduce these impacts while reducing their cancer risks? Obviously fishos spend most of their time out of the water, so they present less of a nanoparticle risk to the environment than do other water users like swimmers and divers who can shed comparatively large amounts of sunscreen into the water. Nevertheless, use of appropriate clothing is important while fishing. Use long sleeved shirts and pants, good quality hats that protect both the face and neck areas, and sungloves for the hands. If you do choose to go for a swim, using rashies or wetsuits can minimise your need to use sunscreens.

Recognition of this problem has also resulted in development of more environmentally friendly products, such as biodegradable sunblocks which contain no nanoparticles or other nasties. One such product that may be worth a look is Mexitan  Coral Safe (, a biodegradable sunscreen which reportedly achieves a SPF 30 rating without nanoparticles or harsh chemicals. Indeed, in some parts of the world biodegradable sunscreens are starting to become mandatory in some tourist spots more heavily used by snorkellers and scuba divers. Maybe this will become the norm in the future if the science continues to point to these “downstream” problems with nanoparticles.




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