The synthetic musks that give a pleasing scent to perfumes and soaps enhance the effect of toxins on the cells of mussels - raising the possibility, researchers say, that the same could be true in humans.

Artificial musk fragrances, like other consumer-product chemicals, have been tested for safety and are not themselves toxic. However, the concern from the new findings is that the fragrances could help harmful substances gain entry into body cells, according to Dr. David Epel of Stanford University in California, senior author on the study.

Epel’s team found that when gill tissue from mussels was kept in musk-containing water for 2 hours, it impaired the workings of so-called efflux transporter proteins - pumps in the cell membrane that normally keep unwanted substances out.

Epel described these transporters as the “bouncers” at the cell’s door. Cells have many layers of defense, he told AMN Health, but the mussel experiments suggest that synthetic musks could “block the first line of defense.”

Whether the findings apply to people is not yet known, according to Epel, who said he and his colleagues are set to do research with human cells.

Artificial musks are used in a wide variety of consumer products, from perfumes and cosmetics to detergents and air fresheners. Musk compounds, Epel noted, have been found in human fat tissue, blood and breast milk.

For their study, reported in the January issue of the journal Environmental Health Perspectives, Epel and colleague Till Luckenbach tested the effects of six types of synthetic musks. They found that after mussel gill tissue had been incubated in a water-musk solution for 2 hours, the cells in the tissue took in much higher than normal levels of a fluorescent dye - a substance that would normally be recognized as an unwanted guest and ejected by the cells’ efflux transporters.

These effects lasted up to 48 hours - a surprisingly long time, according to the researchers.

Epel said the findings raise questions about other common household chemicals - whether, though non-toxic themselves, they may hinder the cellular defense against substances that are toxic.

Right now, Epel said, consumer-product chemicals are not tested for that possibility. If further study bolsters the current findings, he noted, it would suggest another step in safety testing is warranted.

In a written response to the findings, the Fragrance Materials Association, an industry group, said that testing under such lab conditions is difficult to extend to aquatic wildlife, let alone humans.

“Extrapolating these observations in excised gill tissues of mussels to humans is highly speculative, with very little evidence to support such a claim,” it said.

SOURCE: Environmental Health Perspectives, January 2005.