Those fragrant soaps and shampoos we casually rinse down the drain may be causing long-term damage to aquatic wildlife downstream by interfering with the animals' natural ability to eliminate toxins from their system, according to a new Stanford University study published by the National Institutes of Health (NIH).
Writing in the NIH journal Environmental Health Perspectives, Stanford scientists described the biological damage that occurred when they exposed California mussels to synthetic musks--chemical compounds that are used to enhance the smell of detergents, soaps, shampoos, air fresheners, deodorants, cosmetics and other personal care products.
"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."
First line of defense
In their study, Luckenbach and Stanford biologist David Epel tested six synthetic musk compounds widely used by industry. Their goal was 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, the Jane and Marshall Steel Jr. 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, gills were carefully 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 special red fluorescent dye. Under normal conditions, 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. That's exactly what the researchers observed, even two days after the gills had been washed clean.
"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."
These results indicate that even short-term events, such as chemical spills and storm-water runoffs, could have long-term effects, Luckenbach added.
The study also has implications for human health. "People have these same transporters in the blood-brain barrier, the placenta and the intestines," Luckenbach explained. "Perhaps exposure to chemical fragrances could compromise the transporters, making it easier for pollutants to enter the brain, for example."
Concerns about the environmental impact of drug products and 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."
Pharmaceuticals, such as estrogens, antibiotics and antidepressants, often pass through the body without being fully metabolized, Luckenbach noted. "A lot of them are just dumped into the toilet, and that's how they get into the environment."
Worldwide production of synthetic musks increased from about 7,000 to 8,000 tons a year between 1987 and 1996, the authors wrote. Use of musk xylene, the most common industrial fragrance, was prohibited 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's still widely used in the United States, except in lipsticks and other products that are applied orally. One problem for consumers is that, when a product has the word "fragrance" on the label, the actual chemical compound is rarely listed.
"The musks are an example, but this group of pharmaceuticals and personal care products consists of thousands of different chemicals," Luckenbach said.
"One of the assumptions about these chemicals is that they are regarded as environmentally low risk compared to pesticides and oil products," Epel noted. "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 experiment was conducted in Epel's laboratory at Stanford's Hopkins Marine Station in Pacific Grove, Calif., 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.
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