ENS) -- When they are washed down the drain, synthetic fragrances in soaps and shampoos are damaging the ability of aquatic wildlife downstream to eliminate toxics from their systems, according to a new Stanford University study published by the National Institutes of Health (NIH).

The first study to show that some personal care products in water have an effect, even in low concentrations, suggests that humans may be harmed too. The synthetic fragrances can block the ability of human cells to clear themselves of other substances that could be much more toxic than the fragrances.

California mussels exposed to synthetic musks -- chemicals used to enhance the smell of detergents, soaps, shampoos, air fresheners, deodorants, cosmetics and other personal care products -- cause biological damage that is long lasting and may be irreversible, the scientists demonstrated.

"Synthetic musks can be easily produced and are very cheap," said Stanford postdoctoral fellow Till Luckenbach, lead author of the study. "They get into the environment through sewers and drains, but wastewater treatment plants are not equipped to handle them."

These chemicals are found in aquatic environments where they are persistent and accumulate in the organisms.

Luckenbach and Stanford biologist David Epel tested six synthetic musk compounds used by industry to determine if these artificial fragrances affected the animals' "xenobiotic defense system," a biochemical process that allows cells to get rid of poisons and other foreign substances.

"This is the first line of defense used by all cells," said Epel, a Stanford professor of marine sciences. "It consists of a special protein, called an efflux transporter, that's embedded in the cell membrane and pumps out toxins that get into the cell."

For the experiment, described in the NIH journal "Environmental Health Perspectives," gills were sliced from living mussels and placed in water containing very low concentrations of synthetic musks -- 300 parts per billion or less. After two hours, the gills were removed and washed.

To see if this short term exposure affected the animal's defense system, the gills were placed in musk free water with a red fluorescent dye.

Usually, an efflux transporter will recognize the dye as a foreign substance and remove it. But if something interferes with the transporter, the dye will accumulate inside the cell, which causes it to appear brighter. The researchers found that even two days after the mussel gills had been washed clean, they could not remove the dye.

"What we found is that musks are harmful in the sense that they compromise the defense system and let other chemicals in that could be more harmful," Epel said. "The amazing thing is that, even if you wash the chemical fragrance away, there's a long term effect up to 48 hours after removal," he said. These results indicate that even short term events, such as chemical spills and stormwater runoffs, could have long term effects, Luckenbach said. Human health is also at risk, the scientists believe. "People have these same transporters in the blood-brain barrier, the placenta and the intestines," Luckenbach said.

"Perhaps exposure to chemical fragrances could compromise the transporters, making it easier for pollutants to enter the brain, for example," he suggested.

One problem for consumers trying to avoid synthetic fragrances is that only the word "fragrance" appears on the label as a rule. The actual chemical compound is rarely listed.

"One of the assumptions about these chemicals is that they are regarded as environmentally low risk compared to pesticides and oil products," Epel observed.

"This is the first study to show that some personal care products in water do have an effect, even in low concentrations. Our results indicate that the effects on the first line of defense might be irreversible or continue long after the event. 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 these defense systems in aquatic organisms? And could they be having similar effects in humans?"

"The musks are an example, but this group of pharmaceuticals and personal care products consists of thousands of different chemicals," Luckenbach said.

The experiment was conducted in Epel's laboratory at Stanford's Hopkins Marine Station in Pacific Grove, California and was funded by the German Academic Exchange Service, the National Oceanographic and Atmospheric Administration, the California Sea Grant College and the California State Resources Agency.

Worldwide production of synthetic musks increased from about 7,000 to 8,000 tons a year between 1987 and 1996, the authors wrote.

Concerns about the environmental impact of synthetic fragrances first surfaced about 10 years ago in Japan and Europe. "They were picking up pharmaceutical and personal care products in the wastewater flowing into rivers," Epel said. "In Japan they found them in mussels and fish and discovered they are somewhat persistent -- they don't break down."

Use of musk xylene, the most common industrial fragrance, was banned in Japan several years ago after traces of the compound were found in human body fat, breast milk and blood.

Germany has placed a voluntary ban on musk xylene, although it is still widely used in the United States, except in lipsticks and other products that are applied orally.

These findings extend those of a National Research Council report commissioned by the EPA and published in July 2002 that reassesses the environmental disposition of sewage biosolids, particularly odorants, such as synthetic musk.

"For odorants," the NRC report states," the need for further evaluation is driven by he high level of public concern, as well as very limited characterization of the odorants present in biosolids and their toxicity."

"For odorants commonly present in biosolids, the NRC committee wrote, "EPA should move aggressively to develop acute toxicity values for use in assessing the risks posed by these chemicals and should support research on the interaction between these chemicals and pathogens in causing human disease."

The U.S. Environmental Protection Agency has information about exposure to chemicals in personal care products at the National Exposure Research Lab.

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