NIST chemist Michelle Saunders, who worked on creating the dust sample, said the dust would be used mainly by laboratories in their studies on the health effects of household dust.

"Labs involved in testing household dust would use this to be sure of their methods," Saunders said.

The sample of house dust contains traces of about 100 organic compounds that are increasingly appearing in U.S. and Canadian households. Some common everyday organic molecules include oil, gasoline, charcoal and pesticides, said NIST spokesman Michael Baum.

"It's not the same organic as the chicken in the supermarket. You're dealing with chemists -- to a chemist organic means your dealing with carbon-bearing molecules," he said.

The dust contains traces of possible cancer-causing compounds like polycyclic aromatic hydrocarbons produced by car exhaust, garbage incineration and the burning of fossil fuels.

According the The Agency for Toxic Substances and Disease Registry, long-term exposure to PAHs can increase the risk of cancer and also lead to reproductive difficulties.

Another chemical group in the dust is polychlorinated biphenyls (PCBs), which were banned in 1977 by the U.S. government because of their harmful effects on reproduction in many animal species, including humans. PCBs are best known for their contamination of the upper Hudson River ecosystem because of dumping prior to 1977.

The dust also contains traces of polybrominated diphenyl ethers (PBDEs), commonly found in fire-retardant coatings used on household furniture and electronic circuits.

The European Union banned PBDEs in 2004 following a study by Swedish scientists from 1996 to 2001 that showed PBDEs had risen in breast milk over that period. PBDEs have been associated with increased risk of cancer and can be especially prevalent in breast-feeding infants and toddlers who come into contact with household dust.

A U.S. government survey in 2004 found high concentrations of PBDEs in 17 Washington and Charleston, S.C., homes.

Professor Heather Stapleton of Duke University's Nicholas School of Environment, lead author on the study, said that even though it focused on 17 volunteer homes, the data is representative of all homes in Washington and the United States.

"The study covered a variety of homes -- townhouses, apartments, condos," Stapleton said. "Several other studies done since mine have found the same things."

The basis for the SRM 2585 dust composition came from a study done by the Environmental Protection Agency in 1993 and 1994 that collected dust from vacuum-cleaner bags in households, motels, hotels and cleaning services in North Carolina, Maryland, Ohio, New Jersey, Montana and Wisconsin.

Baum said the lack of other states in the sample was not significant because the dust sample is meant to calibrate equipment. "It gives them (users of the sample) a handle of how well their equipment is working," he said.

NIST said the dust samples would not put scientists handling them at risk for cancer, only eye irritation from eye contact with the dust and lung irritation if they accidentally inhaled the dust -- something NIST does not recommend.

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