For two decades you’ve heard that “perc,” the solvent used in dry cleaning, is effective but toxic. Yet consumers searching for a clean alternative won’t find many options.

Perchloroethylene, a nonflammable, colorless liquid with a sharp, sweet odor, has been used for a half-century. It remains the cleaning agent of choice for about 85 percent of 30,000 dry cleaners operating in the United States.

One emerging alternative - silicon-based solvents - is not proven as totally safe.

• Silicon-based solvents. D5 is an odorless, colorless liquid used to dry clean clothes under the name of GreenEarth. D5 contains no organic chemicals, and initial studies showed it to be non-toxic. It is not a skin irritant and, like hydrocarbons, doesn’t fall under any U.S. environmental laws.

It has been used for decades in personal care items such as underarm deodorants, cosmetics, shampoos and creams, said Tim Maxwell, president of GreenEarth, a Kansas City-based company.

A 2003 industry-financed study concluded exposure to D5 raised cancer risks in rats. But Silicones Environmental, Health and Safety Council, an industry trade group based in Virginia, says people likely face no increased risk, due to biological differences between rats and humans. The Environmental Proection agency awaits more information from manufacturers before doing a formal analysis of the compound’s risks.

• Wet cleaning. A 2007 California study calls wet cleaning - more like traditional washing - the greenest alternative to perc. Cleaning agents cost less, equipment lasts longer, electricity use drops, hazardous-waste disposal costs are eliminated, and water use doesn’t significantly change, says the comparision to traditional dry cleaning.

While dry cleaners have long hand-washed some delicate garments, wet cleaning brings that process into the digital age, using computer-controlled washers and dryers and specialized finishing equipment. Currently, only about 80 full-time professional wet cleaners operate across the nation, most in California, where government subsidies are available for cleaners who adopt the process.

Dry cleaners who still use perc say they take steps to eliminate risks to customers and the environment.

“It all depends on the operator,” Pappas says. “All solvents are safe, as long as you know how to use them.”

Toxicity well known

Health experts agree that perchloroethylene is hazardous. Among its reported effects:

• Dizziness.

• Skin, eye and respiratory-tract irritation.

• Damage to central nervous system, liver and kidneys

• Reproductive and childhood-development problems.

The International Agency for Research on Cancer classifies it as a probable cancer-causer in humans. The Environmental Protection Agency calls it a toxic air pollutant. The chemical pollutes outdoor air and ground water as well.

How can a consumer minimize risk?

First, check on how your dry cleaner handles garments. George Pappas, who owns Palo Verde Cleaners in Tucson, Ariz., says he hangs perc-cleaned clothes on a line for 24 hours before giving them to the customer to allow the solvent to evaporate and reduce the chance that customers will be exposed to toxic residues.

If your clothes smell like chemicals when you pick them up, do not accept them until they have been properly dried, the EPA says.

At home, air out clothes again for a time to let chemicals dissipate before hanging clothes in a closet, the EPA recommends.