 nvironmental pollutants that are known
to cause cancer in rat mam- mary tissues are present in human breast milk,
according to scientists in Canada. It is the first time that aromatic amines
(AAs), which are used in many industrial processes, have been detected in
human milk.
 Researchers are not yet sure of the
implications of the finding, saying it needs further investigation, but
expressed concern that the substances may be a cause of breast cancer as
well as a risk to nursing infants. They stress that the nutritional benefits
of breast feeding still outweigh the risks.
The finding is explained in the web
edition of the peer-reviewed journal Chemical Research in Toxicology, published
by the American Chemical Society the world's largest scientific society.
"Chronic exposure of the general
population to AAs is a matter of public health importance," write P.
David Josephy and Lillian DeBruin from the University of Guelph along with
Janusz B. Pawliszyn at the University of Waterloo. "The presence of
AAs in human milk implies that breast ductal epithelial cells, the target
of mammary carcinogens, are also exposed."
AAs are used in the production of
plastics, dyes, pesticides, and pharmaceuticals. Environmental sources for
AAs include in industrial waste, air and water pollution, tobacco smoke,
and some foods.
The study tested milk samples from
31 lactating mothers living near Guelph in Ontario, 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. Surprisingly, levels
did not vary between smokers and nonsmokers. Finding one particular AA,
o-toluidine, may be of special significance because it is known to induce
mammary tumors in female rats.
"We need to discover the major
sources of these exposures," says Josephy. "Control of such exposures
might ultimately help to lessen breast cancer risk, and possibly the risk
of some other cancers."
Also troubling is the possibility
that infants are being exposed to carcinogens through breast milk. However,
Josephy adamantly adds, "Our results should in no way be taken to discourage
breast-feeding, which has great health benefits for babies regardless of
these trace contaminants."
The scientists plan to broaden their
research to include women in other geographical areas. Previous studies
have shown large variations in the breast cancer incidence, with especially
high rates in the industrialized northeastern United States.
This research was supported by the
Canadian Breast Cancer Foundation.  | 
