Campus News

Published by Communications and Public Affairs (519) 824-4120, Ext. 56982 or 53338

News Release

December 17, 1998

Guelph researcher finds carcinogens in human milk

For the first time, University of Guelph researchers have discovered environmental pollutants in human milk that are known to cause cancer in rat mammary tissues.

The finding is explained in the journal Chemical Research in Toxicology, published by the American Chemical Society, the world's largest scientific society. The journal issue will be published Dec. 21.

While researchers stress that the benefits of breastfeeding continue to outweigh the risks, they expressed concern that the substances, aromatic amines (AAs) may be a cause of breast cancer as well as a risk to nursing infants.

"To me, it is a yellow flag, an indication that this is something that should be looked at. It calls for more research," said David Josephy, a professor in the Department of Chemistry & Biochemistry at the University of Guelph. Josephy was the senior researcher on the project, which also included U of G graduate student Lillian DeBruin and Janusz B. Pawliszyn from the University of Waterloo's Department of Chemistry.

AAs are intermediates used in the chemical synthesis used to produce plastics, dyes, pesticides and pharmaceuticals. Environmental sources for AAs include industrial waste, air and water pollution, tobacco smoke and some foods.

Josephy and his colleagues tested samples from 31 lactating mothers living near Guelph, none of whom reported occupational exposure to AAs. All of the samples contained levels of AAs, ranging from less than 0.01 to 7.44 parts per billion. One of the AAs detected, o-toluidine, is known to induce mammary tumours in female rats.

Researchers have long known that AAs are present in human urine, but this is the first time human milk was examined and the carcinogens identified. "It is a new angle," Josephy said. "We were interested in the implications this has for breast cancer."

The researchers hope to receive additional funding to expand the study and examine whether there is a direct link between the identified carcinogens in human breast milk and breast cancer. "The presence of AAs in human milk implies that breast ductal epithelial cells, the target of mammary carcinogens, are also exposed," Josephy said.

Although infants may be exposed to carcinogens through breast milk, Josephy said it is not a reason to cease breastfeeding. "We have no idea whether there as much or more contaminants in infant formulas, we cannot necessarily assume that the alternative is better."

The research was supported by the Canadian Breast Cancer Foundation.

Contact: Prof. David Josephy, Department of Chemistry and Biochemistry, University of Guelph, (519) 824-4120 Ext. 3833 or 4590
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