Studies indicate that all human beings alive today carry traces of many industrial chemicals in their bodies. Some of these substances enter during fetal development or infanthood, carried by maternal blood and breast milk. In addition, we inhale airborne pollutants, ingest pesticide residues and chemical additives with our food and drinking water and absorb others through our skin. Exposure can happen in the workplace, outdoors or inside homes and schools.
Some so-called "chemical body burdens" in humans are harmless, but others can cause cancer, birth defects, developmental problems and other serious health impacts. Many are still being studied. The presence of a chemical in the body does not necessarily mean it will cause harm, but scientists say chemical exposure is pervasive in modern society, and they underscore the importance of testing widely used chemicals for toxic effects.
"I find it remarkable that in this day and age one of the primary ways by which the toxic effects of chemicals are discovered is still the 'body in the morgue' method," writes epidemiologist and former assistant secretary of Energy David Michaels. "An industrial worker dies from some very unusual condition, and we ask why. Well, some of us ask."
For example, Michaels notes, chemical companies that make diacetyl (the main ingredient in artificial butter flavor) did not know that breathing the compound could cause lung damage until workers in popcorn factories became ill. Manufacturers had been required to test diacetyl as a food ingredient, but not as an airborne contaminant in the workplace.
An Inuit woman in Iqaluit, Nunavut, Canada, dries a caribou skin. Toxic chemicals remain a major threat to traditional ways of life in the Arctic. (AFP/Getty Images/Andre Forget)
According to a 2005 report from the Centers for Disease Control and Prevention (CDC), well over 100 chemicals are present in Americans at detectable levels, including heavy metals like cadmium and mercury, phthalates and many pesticides. Levels of some chemicals have fallen in recent years, notably lead (which has been banned from gasoline and house paint) and substances found in secondhand cigarette smoke.
Others are more worrisome. For example, the CDC found that almost 6 percent of women of childbearing age had blood levels of mercury that were borderline dangerous. Mercury is a potent neurotoxin that can cause birth defects, nervous system damage and other harmful effects. It is emitted into the air from sources including coal-burning power plants and incinerators, then falls back to the surface and concentrates in the food chain. Humans are exposed mainly by eating fish that contain high amounts of mercury.
Another 2005 study commissioned by two advocacy organizations, Commonweal and the Environmental Working Group, tested umbilical cord blood from 10 babies born in U.S. hospitals during the previous year. Researchers found an average of 200 industrial chemicals and pollutants in the samples, including mercury, environmental pollutants known as dioxins and pesticides. This study showed that pollutants cross the placenta from mother to fetus as infants grow in utero, exposing the gestating infants to a complex mixture of chemicals during critical months of development.
Living far from industrial sources does not necessarily make people safer from exposures. Indigenous peoples in the Arctic have some of the highest body concentrations of mercury, PCBs and other pollutants of any region on the planet, thanks to global wind patterns and ocean currents that carry pollutants to the poles. Inuit, Aleut, and other native people in Greenland, Alaska and Canada eat large quantities of locally caught meat and fish, which contain high concentrations of chemicals.
Recent studies show that concentrations of some toxins in Arctic food animals are stabilizing, thanks to international agreements limiting use of some of the most hazardous chemicals. However, toxic chemicals remain a major threat to Arctic indigenous peoples' traditional way of life — an ironic fate for people who neither produce nor use most of these products.