Like many 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 that she didn’t have access to the proper equipment to pull off the experiment.

So, like many teenagers, the sophomore at Bishop O’Connell High School in Arlington County 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 what started out as something to “sponsor the kid’s curiosity” prompted a chain reaction in the university lab: an e-mail exchange, an invitation to collaborate and, this week, 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 wool, cotton and polyester 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” to see how much of the chemical persists, 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 at seven Northern Virginia dry cleaners. The 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 dry cleaning solvent that has been 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 Tuesday in Environmental Toxicology and Chemistry.

Between 65 percent 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.

Previous research on the chemical has focused on the effects of inhaling vapors in dry cleaning shops. Previous studies have also tried to determine what might be in the air of a closet, or the air of a room, without knowing how much was in the clothes to begin with, or how long ago the clothes were dry cleaned, Roepe said.

Based on the findings in their study, the Georgetown researchers calculated that levels of the chemical could be higher than previous studies might suggest, 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 the workplace exposure limits set by the Occupational Safety and Health Administration 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.

Adam Finkel of the University of Pennsylvania law school faculty, former director of health standards for OSHA, said the findings suggest that someone who delivers dry cleaning for a living could face higher exposures than workers in a plant.

“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.

The EPA does not have a specific standard for perc in clothing, but the agency is revising its rule, according to an agency official.

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, who has studied levels of the chemical in indoor air, said that argument was subject to debate because industry representatives have said in the past that pressing garments does not contribute significantly to indoor levels of perc. The chemical is either in the clothing or going into the air, she said. “It doesn’t just disappear.”

In the study, researchers found that cotton and polyester absorption of the chemical leveled off after two or three cleaning cycles but that levels in wool increased with each of six cycles. Silk, by comparison, did not retain appreciable levels. Researchers found perc levels of up to about eight micrograms in five square centimeters of fabric.

Paul Dugard, a toxicologist at the Halogenated Solvents Industry Alliance, which represents manufacturers of perchloroethylene and other chlorinated solvents, said it’s not surprising that some perc is found in clothing after dry cleaning.

But the amounts in the study are “an exaggeration” of what would exist in real life, he said. Because of better technology, the dose in clothing is “so low that I would have no concerns about it whatsoever,” he said.

Public health experts said organic or “green” cleaners might be using hydrocarbons instead of perchloroethylene. But hydrocarbons also have toxic properties. Two cleaners in the study advertised themselves as “green,” and researchers found no detectable levels of perc in any fabric from those shops. But one did show evidence of hydrocarbons, which are components in kerosene and gasoline.

A safe alternative, experts said, is carbon dioxide that has been compressed to a liquid.

Dantzler, now 16 and a junior, said that she came up with the idea when she was a freshman and that she reached out to Roepe last fall.

“I was really grateful they would take me in and allow me to use their lab,” she said. “It was really cool that they would say, ‘Sure, come on over.’ ”

She kept track of the dry cleaning pickup and drop-off dates in a marble composition notebook. At Georgetown, she learned to use gas chromatography and mass spectrometry to measure the amount of chemical in the fabric patches.

“It was exacting,” she said. “Very analytical, very precise.”

She received a top score — 100 — on her school research paper. Her project won first place in chemistry at last year’s Arlington County science fair, and she hopes to enter it in the prestigious Intel International and Engineering Science Fair this coming year.

She also wants to keep testing clothing at dry cleaners in the District and Maryland.

Dantzler, who wants to become a doctor, 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.”

Staff writers Juliet Eilperin and Christian Torres contributed to this report.