Beach showers pollute the ocean

This article was originally presented on Hakai magazine, Online Journal of Science and Society in Coastal Ecosystems. Read more stories like this at

At 49 Black Sand Beach, in Honoka’ope Bay, Hawaii, there is a strange moated mound in the middle of the beach. This little island, made of sand piled up about half a meter or so high, was built from a beach shower. Every time a beachgoer steps into the shower to rinse off, the water runs off their base, gouging gullies in the sand.

But while the apparent effect of showering on the beach is mostly benign, it belies subtler and potentially more destructive consequences.

Water flowing from a shower into the nearby surf is laden with a toxic mix of pollutants – including UV filters, microplastics and parabens, new research shows. Scientists who tested the water say this beach shower, like thousands of others scattered along coastlines around the world, is a source of pollution that sends chemicals leaking into the ocean in concentrations high enough to cause serious damage to marine life.

The problem, says Craig Downs, an ecotoxicologist at Haereticus Environmental Laboratory in Virginia who co-authored the new paper, is that most beach showers don’t drain into the local sewage system. Instead, runoff flows onto land and into the ocean.

Swimmers throw large amounts of sunscreen and other pollutants into the ocean, and scientists have collected a lot of evidence that these pollutants can harm marine life. But the concentrations of pollutants coming off the beach showers, Downes explains, are startlingly high. Beach showers, Downes says, are point sources of pollution that can cause concentrations of pollution that seriously threaten native corals, crustaceans and fish. King tides and monsoons can raise these concentrations even further, when all the pollutants built up in the sand are released in one giant pulse.

Because showers are point sources of pollution, Downs and his colleagues argue that their owners and operators — who are mostly municipalities — could be sued for violating the U.S. Clean Water Act.

However, Downs would like to see the situation more proactive. “We really don’t want to get rid of the showers,” he says. Instead, “what we can do is implement technology or legislation to end it [the showers] as a source of pollution.”

Fixing the showers won’t be easy, though. Placing beach showers in municipal sewage systems will not work: beach sand can clog traditional sewage treatment systems. Municipal systems are also not built to remove such high levels of these pollutants.

However, there are technologies that will work.

One option for dealing with high pollutant levels in beach showers, says Ranil Wickramasinghe, a chemical engineer at the University of Arkansas who was not involved in the study, is to use a membrane bioreactor. This complete wastewater treatment system uses a thermoplastic or ceramic membrane to trap contaminants and allow clean water to flow through. Microbes absorb pollutants, rendering them harmless. But there are a few catches: setup costs are high, and microbes must be tailored to each contaminant.

Another possibility, says Carlos Martínez-Huitle, an environmental electrochemist at Brazil’s Federal University of Rio Grande do Norte, who was also not involved in the research, uses advanced oxidation processes (AOP). There are two modes that can be used in showers, he says: direct AOP, where electricity is applied to the AOP cell, allowing the material on its inner surface to break down pollutants; or indirect AOP, where the current draws pollutants to one end while oxidants form at the other. Oxidizers then convert the pollutants into benign compounds. Municipalities could collect wastewater from showers, filter the sand and then apply an AOP device to clean up the pollutants before discharging the water into the ocean, Martinez-Huitle suggested.

However, AOP is an energy-intensive technology, so the key is to pair it with a renewable energy source. In their lab, Martinez-Huitle and his team have developed a system that uses AOP to clean industrial wastewater with electricity supplied by solar panels or wind turbines.

But even the most cost-effective wastewater treatment technology will test tight municipal budgets. Agreeing on which one to use and then implementing it will also take time.

In the meantime, researchers hope that consumer education, increased use of UV protection factor (UPF) clothing, and regulations such as Maui’s impending ban on chemical sunscreens will help stem the flow of pollutants into the environment.

For Downs, once we know that beach showers can be powerful sources of pollution that can threaten marine life, the next steps are obvious. “If you can identify a point source of pollution,” says Downs, “then you have … the responsibility to mitigate that pollutant.”

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