13 July 2005

Synthetic fragrances harmful to marine life, study says

Synthetic fragrances commonly added to perfumes, soaps, shampoos, and dozens of other personal health care products are proving harmful to the marine environment and potentially to humans as well, according to marine scientists.

California mussels were used as guinea pigs to test the effects of synthetic fragrances on cells. Scientists determined that the presence of synthetic fragrances in water overwhelmed the mussels' ability to defend themselves from toxins.Also known as synthetic musks, the chemical compounds reportedly compromise a cellular defense mechanism that normally prevents toxins from entering cells. The mechanism is controlled by efflux transporter proteins embedded in cell membranes.

"Efflux transporters are like bilge pumps in a ship. Another analog is bouncers—these guys at the nightclub," said Till Luckenbach, a postdoctoral fellow at Stanford University's Hopkins Marine Laboratory in Pacific Grove, California.

The transporters recognize and pump out many kinds of toxins from cells, but if too many chemicals are around, the capacity of the transporters can be overwhelmed.

This is a potential danger in the presence of foreign compounds such as synthetic fragrances, Luckenbach said. The fragrances themselves are nontoxic, but by overwhelming the cellular bouncers, the fragrances allow unwanted toxins to slip by and contaminate the cell.

According to Luckenbach, this is a novel mechanism by which a wide range of presumably nontoxic chemicals could have a negative impact on plants and animals.

Together with Stanford biology professor David Epel, Luckenbach demonstrated the effect of these synthetic fragrances in experiments on California mussels.

Mussel cells share properties with some human cells, such as the cells found in a barrier that prevents toxins from entering the brain, Luckenbach said.

"We can't conclude that these [compounds] are having the same effect on humans, but we think it's something we should test," he said.

Luckenbach and Epel published their findings this January in Environmental Health Perspectives, a journal of the U.S. National Institutes of Health.

Mussel Experiments
According to Luckenbach, wastewater treatment plants fail to break down synthetic musks, allowing the compounds to spill into rivers and oceans via sewage discharge.

The compounds persist in the environment and have been shown to accumulate in the tissues of fish and other invertebrates.

Despite their pervasiveness, the toxicity and environmental risk of most synthetic fragrances are considered negligible, according to the researchers.

The compound musk xylene is an exception. Its use was discontinued in Japan and Germany and banned in the U.S. from lipsticks and other ingestible products.

In addition to a direct toxic effect, Luckenbach and Epel wanted to know whether synthetic musks pose an indirect health risk by compromising an animal's "xenobiotic defense system"—the process by which efflux proteins remove toxins from cells.

To do this, the researchers sliced gills off living mussels and exposed them to six synthetic musk compounds in water solutions. Musk concentrations were 300 parts per billion or less.

The gills continued to function normally for a week after being sliced off, Luckenbach said. After two hours of exposure to the musk compounds, the gills were removed, washed, and placed in musk-free water with a red fluorescent dye.

Under normal conditions, efflux transporters (the bilge pumps or "bouncers") in the gill tissue recognize the dye as a foreign compound and remove it. If the transporters are impaired, however, the dye can accumulate in the cell.

This is what the researchers observed: Gills exposed to synthetic musks accumulated dye at much higher concentrations than gills not exposed to musks.

"We think these transporters are just overwhelmed. Their capacity is overstretched and they can't work properly," Luckenbach said. The cells, the researchers added, were impaired for up to 48 hours after exposure to the compounds.

The finding is troubling, the researchers note, because there are many other synthetic chemicals in the environment that may work in a similar way.

"It's a warning sign. It's a smoking gun. Are there other chemicals out there that have similar long-term effects? Could these be harming defense systems in aquatic organisms? And could they be having similar effects in humans?" Epel asked in a media statement.

Consumer Beware?
Before this project started, Luckenbach said, he knew nothing about synthetic musks. Now that he's aware of the potential health hazard, he looks at the ingredients in health care products and is surprised by the lack of information he finds.

"In lot of cases you don't know what's in the product. They usually say 'perfume' or 'fragrance' but do not specify the compounds," he said. Some products are labeled as synthetic free or made with nonsynthetic ingredients like lime, he added.

In a statement prepared in response to the study, the Fragrance Materials Association of the United States, a Washington, D.C.-based organization, said synthetic musks are safe for consumers.

"[They] are among the most thoroughly researched and tested fragrance ingredients. Their safety for human health has been extensively tested and affirmed by numerous regulatory agencies and academic scientists around the world," the statement reads.

The association did not return a phone call seeking further comment.

Source: news.nationalgeographic.com


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