Like many other memorable science fair projects, it began with a startlingly simple idea: Find out what chemicals remain in dry-cleaned clothing.

But the problem facing 15-year-old Alexa Dantzler was she didn’t have access to the proper equipment.

So the Arlington, Va., high school sophomore went online. She e-mailed three or four chemistry professors across the country, asking for help. Only Paul Roepe, then-chairman of Georgetown University's chemistry department, seemed intrigued. He took on the research "for fun,'' he said.

But that prompted a chain reaction in the university lab: an e-mail exchange, an invitation to collaborate and, last month, a paper published online in a peer-reviewed environmental journal. The paper gives new details about the amount of a toxic chemical that lingers in clothing after it is dry-cleaned.

"At the end of the day, nobody, I mean nobody, has previously done this simple thing— gone out there to several different dry cleaners and tested different types of cloth,'' said Roepe, who supervised the study.

Dantzler, with help from her mother, sewed squares of wool, cotton, polyester, and silk into the lining of seven identical men's jackets, then took them to be cleaned from one to six times. The Virginia cleaners, who were not identified, had no prior knowledge of the experiment.

She kept the patches in plastic bags in the freezer — to preserve the samples — and went to Georgetown once or twice a week to do the chemical analysis with two graduate students, Katy Sherlach and Alexander Gorka. The research team found that perchloroethylene, a solvent linked to cancer and neurological damage, stayed in the fabrics and that levels increased with repeat cleanings, particularly in wool. The study was published online in Environmental Toxicology and Chemistry.

Between 65 and 70 percent of the country's estimated 25,000 dry cleaning facilities use the solvent, known as PCE or perc, industry representatives said. Government regulations and voluntary industry guidelines exist for atmospheric concentrations in the workplace, and there has been a long-running fight between environmentalists and the federal government over how quickly the chemical should be phased out for dry cleaners.

No standards exist for levels in dry-cleaned fabric, public health experts said.

Without further research, Roepe said, it was difficult to say how much risk consumers might face from wearing, say, dry-cleaned wool pants for a year or breathing air from a closet full of dry-cleaned clothes.

"Like cigarettes, like UV sun exposure, the risk depends on how much and how long,'' he said.

Using the levels found in the patches, researchers calculated what they thought would happen if four freshly cleaned wool sweaters were put inside a warm car with the windows closed for an hour: The perc vaporized from the sweaters would produce a level as high as 126 parts per million, which exceeds workplace exposure limits and far exceeds tighter limits more widely recommended by industry and government scientists.

Public health experts said the study raises important questions about how much PCE is retained in dry-cleaned clothes and then breathed in or absorbed through the skin.

"The next step should be for somebody to look at human exposure to wearing dry-cleaned clothing and get an idea of how much is actually taken into the body,'' said Judith Schreiber, chief scientist for the environmental protection bureau in the New York state attorney general's office.

Industry representatives said the study was incomplete because the tested garments had been dry-cleaned but not pressed. Blowing steam through garments to get rid of wrinkles helps remove residual solvent, said Mary Scalco, chief executive of the Dry Cleaning and Laundry Institute, an industry association. Few consumers choose dry cleaning without pressing, she said.

Schreiber said that argument was subject to debate. The chemical is either in the clothing or going into the air, she said. "It doesn't just disappear.''

Dantzler, now 16 and a junior, wants to be a doctor. She said she learned valuable lessons during the project.

"I know procedure is very important during surgery,'' she said. "In the lab, I really learned to be aware of what I was doing.''

(Washington Post staff writers Juliet Eilperin and Christian Torres contributed to this report.)

Copyright 2011 The Boston Globe