Dolphins are swimming in waters tainted with triclosan, an ingredient in antibacterial soaps and other products, but they aren't winding up squeaky clean
Brett Israel and Environmental Health News, Scientific American 11 Aug 09;
Dolphins are swimming in waters tainted with germ-killing soaps, but they aren't winding up squeaky clean.
Triclosan, an antibacterial chemical found in everyday bathroom and kitchen products, is accumulating in dolphins at concentrations known to disrupt the growth and development of other animals. Scientists have found that one-third of the bottlenose dolphins tested off South Carolina and almost one-quarter of those tested off Florida carried traces of triclosan in their blood. It is the first time the chemical has been reported in a wild marine mammal – a worrisome finding, researchers say, because it shows it is building up in the ocean’s food web.
Triclosan is the germ-killing chemical of choice in hundreds of products, including liquid hand soaps, toothpaste, deodorants and cutting boards. Now some scientists are calling for its removal from consumer products.
“The fact that this chemical is found in the environment and is being detected in a top level predator certainly warrants concern,” said Patricia Fair, a research physiologist at the National Oceanic and Atmospheric Administration and lead author of the dolphin study, which was published online in the journal Environmental Pollution in May.
Scientists cannot say what effect triclosan might have on dolphins, but lab studies conducted on other animals suggest that it could be jeopardizing their health. Studies in bullfrogs found that triclosan disrupts the endocrine system — blocking the tadpoles’ development into frogs at concentrations found in the environment. Another study found triclosan alters thyroid hormones in rats, which is another sign of endocrine system disruption.
Many scientists weren’t surprised to see triclosan turn up in dolphins, due to the chemical’s widespread use. In the United States, 76 percent of liquid soaps and 26 percent of bar soaps contain triclosan, according to a 2001 study in the American Journal of Infection Control. In Europe, approximately 350 tons are used in commercial products.
“With the sheer amount being used, it’s actually starting to accumulate [in more top predators],” said Caren Helbing, a molecular biologist at the University of Victoria, in British Columbia, Canada, who was not involved with the dolphin study.
After spitting your toothpaste down the sink or washing your liquid soap down the drain, it ends up in a sewage treatment plant, where 90 to 98 percent of the chemical is broken down, before the wastewater is discharged into freshwater or directly into oceans along the coasts. Triclosan was one of the most frequently detected chemicals in a survey of streams in 30 states conducted by the U.S. Geological Survey.
Triclosan builds up in fatty tissues, so it passes up the food chain from animal to animal, including humans.
Three-quarters of people tested in the United States have triclosan in their urine, according to a 2008 study by the Centers for Disease Control and Prevention. It also has been found in breast milk of Swedish women. The concentrations reported in humans are similar to those found in dolphins.
Both the U.S. Environmental Protection Agency and the Food and Drug Administration regulate triclosan in consumer products.
Last October, after reviewing the existing science, the EPA decided to approve the chemical for continued use. The EPA said triclosan “may bioaccumulate, potentially posing a concern for aquatic organisms.” But it concluded that the levels coming from households are too low to be toxic to fish or other aquatic creatures.
Nevertheless, the agency added new requirements. Triclosan manufacturers must submit toxicology reports and an environmental monitoring plan. Also, the EPA decided that it will review the chemical again in four years because of “the rapidly developing scientific database for triclosan,” according to an agency document.
“Currently, the Agency intends to begin that process in 2013, ten years earlier than originally planned,” the document says.
In the meantime, Swiss-based chemical company Ciba, the major manufacturer of triclosan, announced in March that within a year it will stop using it for clothing, textiles, plastic and other uses registered with the EPA. The company says its decision was based on market decisions, not concerns over its safety.
Ciba, however, will continue to use the chemical in soaps and other personal care products and medical equipment, “where the proven safety and efficacy of triclosan is most clearly valued by our customers and supported by customer demand,” according to a statement by the company, now part of chemical giant BASF. Those products come under the control of the FDA, not the EPA.
Paul DeLeo, director of environmental safety for the Soap and Detergent Assn., which represents companies with products that contain triclosan, says that the amounts found in dolphins and other animals are too small to have any effect.
In the new study, the levels in 26 dolphins tested in Charleston, South Carolina, and in Indian River Lagoon in Central Florida ranged from 0.025 to 0.27 parts per billion.
Researchers say it’s how triclosan behaves, not the amount, that is critical. As little as 0.03 parts per billion has disrupted the endocrine system of frogs in the laboratory.
“It sounds like a very, very little bit, but in biology that’s in the range that normal hormones work,” said Catherine Propper, an endocrinologist at the Northern Arizona University who studies amphibians exposed to chemicals in wastewater.
The levels found in the environment concern scientists because of triclosan's remarkable biological structure. Triclosan is strikingly similar to thyroid hormone, so it might bind to hormone receptors, said Helbing, author of the frog study. Because frog and mammal endocrine systems are similar, triclosan can potentially “affect how hormones work in ways that aren’t intended” in dolphins, and maybe even humans, she said. Altering thyroid function in humans and animals might cause abnormal brain development and other developmental defects.
But making the leap from bullfrog studies to dolphins, or even humans, is not so simple. Rarely is triclosan the only chemical found in an ecosystem, so pinpointing cause and effect in the wild is a daunting challenge. But scientists say further lab testing can confirm these early findings and paint a clearer picture of triclosan’s long-term effects.
“Dolphins are mammals just like us," Helbing said. "They are telling us about potential health effects. We need to perk up and listen."
Even without triclosan, dolphins carry a chemical cocktail of toxic substances in their bodies. Several other compounds that have built up in ocean animals already have been banned because of concerns about their persistence in the environment and potential health effects in wildlife and people.
In 1990, high levels of PCBs, or polychlorinated biphenyls, which can suppress the immune system, were found in striped dolphins in the Mediterranean at extremely high levels. The pesticide DDT, brominated flame-retardants, perfluorinated compounds and mercury also contaminate dolphins around the world. Wildlife experts say these chemicals place dolphins at risk of reproductive failure and disease. PCBs may have contributed to large die-offs of dolphins in the Mediterranean and along the East Coast of the United States in the 1980s and 1990s.
While most animal studies have focused on these so-called persistent organic pollutants, newly emerging pollutants found in pharmaceuticals and personal care products are under increasing analysis.
“A lot of these compounds are in the environment and they do have impacts on [animals’] physiology. But whether they’ll have impacts on fitness and survival, that needs longer term study,” Propper said.
This article originally ran at Environmental Health News, a news source published by Environmental Health Sciences, a nonprofit media company.
