Odor hazard. Nontoxic fragrances that find their way into the water may prevent mussels from clearing toxins.

Musk and Mussels a Bad Mix

Artificial fragrances are in all sorts of detergents and personal care products, and they tend to pass through wastewater treatments and linger in the environment. Although the chemicals are nontoxic, a new study indicates that low concentrations could be indirectly harming mussels and other aquatic wildlife. These synthetic musks interfere with the transport proteins that pump many kinds of toxins out of cells, which could allow them to build up to dangerous levels. The transport proteins remain impaired for up to 2 days after exposure to the musks.

Other compounds are already known to block these so-called efflux transporters. (One positive application is the development of drugs designed to prevent such transporters from helping cancer cells resist chemotherapy.) Lab experiments have shown that environmental pollutants, such as polyaromatic hydrocarbons, can have the same effect on transporters in sea urchins, fish, mussels, and other aquatic organisms, ultimately leading to toxicity.

Ecotoxicologist Till Luckenbach and marine biologist David Epel, both at Stanford University, examined the effects of six synthetic musk compounds common in personal care products. They removed gills from mussels, then bathed them in water with low concentrations of the musks. Two hours later, they checked for effects on the transporter proteins in the gills by placing them in water containing a red dye. The gills absorbed and retained the dye, showing that the transporter cells had been inhibited. The proteins remained impaired for up to 2 days, then recovered, the pair reports in Environmental Health Perspectives online. "These seemingly innocuous chemicals are harmful in an unexpected way," says Luckenbach.

"They have shown that [musks] can compromise a really important defense system," says Tvrtko Smital, a molecular ecotoxicologist at the Rudjer Boskovic Institute in Zagreb, Croatia. The worry is that musks could allow low-level pollutants to accumulate inside wildlife, he says. "We can expect prolonged effects with exposures to relatively low concentrations of chemicals," says Smital, who adds that it will be important to monitor habitat for these fragrances.

Related sites
The EHP paper
David Epel's lab site