Scientists have long known that certain chemicals like paradioxane can cause cancer. Now we’re beginning to realize that the total of a person’s exposure to all the little amounts of cancerous agents in the environment may be just as harmful as big doses of a few well-known carcinogens. Over a lifetime, cigarettes deliver massive quantities of carcinogens that increase the risk of lung and other cancers. Our chances of getting cancer reflect the full gamut of carcinogens we’re exposed to each day—in air, water and food pollution, and cancerous ingredients or contaminants in household cleaners, clothing, furniture and the dozens of personal-care products many of us use daily.
Of the many cancer risks we face, shampoos and bubble baths should not be among them. Europe has banned the use of paradioxane in all personal-care products and recently recalled all contaminated products. The United States and many other non-European countries have not done so. Whereas Europe tends to follow the precautionary principle—in which the burden is on manufacturers to prove that a product doesn’t harm consumers—most other nations won’t take regulatory action until enough people have already complained of harm. In light of what scientists are learning about exposure to trace chemicals, this makes little sense.
Scientists don’t experiment on humans, for obvious reasons, but we have found some clues from lab and wildlife studies. Medical researchers have demonstrated that trace chemicals of some widely used synthetic organic materials can damage cultured human tissue. The effects don’t just accumulate, they mushroom. UC Berkeley professor Tyrone Hayes has shown that very low levels of pesticide residues in Nebraska cornfields can combine to create male frogs with female features that are vulnerable to infection and can’t reproduce.
There’s plenty of human evidence that combined pollutants can cause more harm together than they do alone. People who smoke, drink and work as painters have much higher risks of kidney cancer than those who engage in only one of these known cancer-causing practices. We also understand that women who use hormone-replacement therapy and drink more than two glasses of wine daily have higher risks of breast cancer than those who engage in only one of these practices. This tells us that other combinations of chemicals in the environment can also lead to other cancers. One in five cases of lung cancer in women today—a disease that kills more women than ovarian, breast and uterine cancers combined—has no known history of active or passive smoking exposure. Rates of non-Hodgkin’s lymphoma and other cancers not tied with aging or improved screening have increased in many industrial countries. Testicular cancer continues to rise in most industrial countries. Childhood cancer, while still rare, is more common than in the past, and most cases occur in children with no known inherited risk of the disease.
The problem, from a scientific standpoint, is that resolving the effects of minuscule levels of chemicals we encounter throughout our lives is part of a complicated puzzle for which many pieces are missing. What scientists need is data—lots of it. Manufacturers, however, tend to hold the precise formulations of products as trade secrets, and most countries don’t require labeling of cancer-containing personal-care products (though efforts in France, Canada and elsewhere to get laws passed are underway). Humans differ from frogs and mice by 10 percent of genes; when a chemical causes cancers in both sexes of two different species of animals, the World Health Organization considers it a probable human carcinogen. We should not let the absence of specific information on the health consequences for our infants and toddlers of single cancer-causing contaminants like paradioxane become a reason to delay getting rid of such hazards. The goal of public-health policy is to prevent harm, not to prove it’s already happened.
