Everyday chemicals may shift ecosystems. (Clean Casualties).

Chemical concoctions used to battle bacteria in kitchens and bathrooms may have unintended victims. The traces of these products that wend their way into U.S. streams may kill off algae, researchers report. Since algae are at the bottom of the aquatic food chain, this effect could have far-reaching consequences.

Over the past decade, household and personal-hygiene products have been made more lethal to bacteria. The antimicrobial agent triclosan pervades products ranging from window cleaner to toothpaste, for example. Scientists suspect that such chemicals may hasten the ascent of drug-resistant bacteria, perhaps worsening the problem already posed by the overuse of antibiotics (SN: 5/27/00, p. 342).

Now, environmental scientist Brittan A. Wilson of the University of Kansas in Lawrence and her colleagues find that antimicrobial-chemical cocktails may also have environmental consequences.

Wastewater-treatment plants often don't remove household chemicals. Therefore, these substances make their way from household drains to natural bodies of water (SN: 8/17/02, p. 101). Treated wastewater has been known to contain up to 40 such chemicals, among them drugs, solvents, and detergents, says hydrologist Dana W. Kolpin of the U.S. Geological Survey in Iowa City. "And that's just the chemicals that we're measuring," he says.

To find out how some of these chemicals may affect freshwater ecosystems, Wilson's team collected algae species from a Kansas stream. In the lab, they treated the algae with one of three household chemicals: triclosan, the antibiotic ciprofloxacin, or tergitol, a spermicidal lubricant and hair dye ingredient. The scientists used the average concentrations of triclosan and ciprofloxacin found in U.S. streams, and an estimated concentration for tergitol. Control samples of algae were left untreated. For 2 weeks, the scientists monitored the number of each algal species in the samples.

Treatment with the chemicals shifted the structure of the algal communities compared with the untreated algae communities, the researchers report in an upcoming Environmental Science and Technology. The number of algal species and overall algal growth dropped in samples treated with each of the chemicals, but not in control samples.

"In the real world, algae are exposed to a complex mixture of these and other chemicals," says ecologist Val H. Smith, a study collaborator also at the University of Kansas. Under those conditions, the effects found for single chemicals may be "greatly aggravated," he notes

"The study is quite significant--maybe even pioneering," says ecologist Ray Drenner of the Texas Christian University in Fort Worth. Wilson and her colleagues "make a case that real-world concentrations of these chemicals likely have effects on the base of the food chain," he adds.

"It's stupid to think that chemicals that keep toothpaste safe from bacteria won't have an effect at the other end of the sewer pipe," says ecologist Stanley I. Dodson of the University of Wisconsin-Madison. "I'm amazed at the effects from such low [chemical] concentrations."