One of the most common questions I get asked is about the health effects of toxic chemicals. Will the chemicals in the landfill harm my children? Will the emissions from the plant cause my family to get cancer? Did the chemicals off-gassing from the PVC flooring cause my son’s asthma? The questions continue every day from people across the country.

Most of what we know about the toxicity of chemicals comes from animal studies and from studies of workers who manufacture the chemicals. From this experience, we’ve learned that dusty air causes lung cancer, benzene causes leukemia, radioactive paint causes bone cancer, vinyl chloride, liver cancer, and certain pesticides cause muscle weakness and paralysis. There’s also limited evidence from studies in communities, especially among children who are highly susceptible to toxic chemicals. At Love Canal, for example, there were high rates of miscarriages and children born with birth defects; in Tucson, AZ, children whose parents drank water contaminated with trichloroethylene (TCE) were born with 2-1/2 times more heart defects than normal; in Toms River, NJ, high rates of childhood cancer was linked to drinking water contaminated with TCE and other solvents; and in Woburn, MA, increased rates of childhood leukemia were associated with drinking contaminated water.

There is no question that exposure to toxic chemicals causes adverse health effects. But for nearly all chemicals there is not enough information on what happens when people are exposed. At best, there’s good information on the toxicity of only about 10% of over 80,000 chemicals in use today.

This makes it very difficult to say with certainty what health effects will occur following exposure to toxic chemicals. Among the uncertainties are how an individual body responds to exposure (this varies quite a lot from person to person), how long exposures occur, how many chemicals you’re exposed to and the actual toxicity of the substance. In most instances, these factors are unknown.

Another confounding factor is that many symptoms or diseases are not specific to a particular chemical. In most instances, there can be many causes of the symptoms that people are having. And since few physicians know much about toxic chemicals, they often tend to blame the victim for his or her situation rather than looking at chemicals as a possible explanation. For example, many physicians will diagnose a person who is fatigued, moody and without appetite as “depressed,” likely to have a problem at home or at work. Seldom is exposure to toxic chemicals considered, even when raised by the patient.

Still another problem is determining the “normal” rate of an illness or disease in a community or in a group of people. Scientists simply can’t decide amongst themselves what is normal, in large part because of the many uncertainties already mentioned.

As a result, evaluating chemical exposures is largely a matter of opinion, not fact. Scientists can give you estimates of risk, or tell you what adverse effects are typically associated with exposure to a chemical, but they cannot tell you with any certainty whether your child will develop cancer because of his/her exposure to TCE or other chemicals in your drinking water. They can give you their opinion, but it’s only an opinion.

This is very frustrating for people. How can we be smart enough to put a man on the moon and bring him back, yet we don’t know much about the toxicity of the sea of chemicals that we live in every day? This speaks volumes about the power of the chemical industry to control government regulations and research agendas.