Eulalee Thompson

Scientists would really do us women a world of good if they would carry out the kind of studies where associations can be confidently made between environmental factors and the development of breast cancer, still the leading cancer in women. This would certainly shift this discussion out of the realm of speculation.

I make these comments after reading yet another study speaking only of 'possible links' between the development of breast cancer and women's widespread exposure to hundreds of chemicals and other environmental contaminants. This study, though extensive and comprehensive, was merely a review of existing research on environmental factors that may increase breast cancer risk. The study was published on May 14, in the online version of Cancer, a journal of the American Cancer Society. It was funded by the Susan G. Komen for the Cure and conducted by the Silent Spring Institute, both U.S.-based organisations. A hard copy of the study will be published in the as a supplement to the June 15 edition of Cancer.

But even though the study does not make any concrete links between environmental factors and the development of breast cancer, women can still be guided by its findings. The researchers identified 216 chemicals that caused breast tumours in animals. They broke down the compounds in this way:

73 are present in consumer products or as contaminants in food.

35 are air pollutants.

25 are associated with occupational exposures affecting more than 5,000 women each year.

29 are produced in the United States in large amounts, often exceeding one million pounds per year.

Food flavourings

To be more specific, some of the identified possible cancer-causing compounds include industrial chemicals, pesticides, plastic softeners, plastic additives, radiation, air pollutants, pharmaceuticals, mutagens associated with chlorine-disinfected drinking water, diesel exhaust and even natural products such as food flavourings.

Though the researchers say that research in the area of the epidemiology of environmental pollutant is sparse, they indicate that results in recent years have begun to show evidence of increased risk, in genetically susceptible women, associated with exposure to polychlorinated byphenols (PCBs) which are banned chemicals previously used in electrical equipment and other products; polycyclic aromatic hydrocarbons (PAHs) which are air pollutants from vehicle exhaust systems (which I have complained about in a series of articles last year) and organic solvents and dioxins.

Pollutants in breast milk

Organic solvents include common chlorinated solvents such as methylene chloride and the scientists say that exposure is common the workplaces and at lower levels from air, drinking water and consumer products.

"Detection of organic solvents in breast milk confirms their availability to breast tissue," the scientists noted in the report.

The scientists say that primary sources of dioxins in the environment are waste incineration, pulp and paper manufacturing and other industrial processes; primary sources of exposure are dietary fat, particularly milk, fish and meat. Occupational exposure occurs in production of phenoxy herbicides and chlorophenols.

The organic solvent and PAHs the scientists identify, based on animal studies, as 'animal mammary carcinogens' and the PCBs and dioxins as 'endocrine disruptors', thus giving some evidence of the biological mechanisms that could link these chemicals to breast cancer. The thinking is that some of these chemicals may act like hormones at low doses.

Drinking water

On the matter of the byproducts produced by drinking water disinfectants, the scientists say that the focus of epidemiologic studies has been on bladder, colon and rectal cancer but there is evidence that MX, a major mutagenic constituent of disinfection byproducts, causes mammary tumours and suggests that breast cancer should be further investigated.

eulalee.thompson@gleanerjm.com