Hesperian Health Guides
Our Chemical Body Burden
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Some chemicals leave the body quickly after a person is exposed. Others may remain in fat, blood, or bones for a long time. For example, arsenic usually stays in the body for only 3 days after a person is exposed 1 time. Other chemicals, such as the pesticide DDT, can stay in the body for 50 years or more. The chemical body burden is the amount of toxic chemicals that are present in the human body at any time.
Just because we have these chemicals in our bodies does not mean that every one of us will get sick. Some people may get sick even though they have few toxic chemicals in their bodies. Others who have more chemicals may not get sick (see How Toxic Chemicals Harm Us).
Children often have a greater body burden than adults. Although they may have a shorter period of exposure because of their age, their bodies have not yet developed ways to protect themselves from toxics or to remove toxics from their bodies.
There are so many chemicals in our environment that often we cannot know which ones we are exposed to or how the combination may affect us. This chemical mixture makes it especially difficult to trace a person’s health problems to chemical exposure. In most cases though, chemical mixtures are more harmful than each chemical by itself.
Scientists study each chemical alone to see how it can harm a person’s health. But many chemical products, such as cleaners, dyes, plastics, paints, and glues, are a mixture of several chemicals. For example, paint contains solvents, pigments, and other materials. Solvents cause 1 set of health problems, and pigments cause another. Mixed together, they can cause a third set of health problems, including ones that each chemical alone might not cause. Most waste from industry, such as smoke from a smokestack or chemical waste dumped into waterways, is also a mixture of many chemicals.
How toxics move through the environment
Many toxic chemicals travel far from their sources through air, water, and food, and in products we use every day, such as plastics, cleaners, and pesticides. Some of these chemicals remain in the environment for a long time. Every person on earth carries toxic chemicals in their bodies.
Toxic chemicals collect in the fat of people and animals, and in some plants. When people or large animals (such as bears, owls, hawks, or large fish) eat smaller animals, fish, or plants, toxic chemicals in them are passed along through the food chain or food web and accumulate in the bodies of those eating them.
Time: ½ hour to 1 hour
Materials: 20 or 30 necklaces made of colored beads. About half are of one color, such as yellow, and the other half have beads of two colors, such as yellow and red.
- Each person takes the role of an animal. We use hawks, mice, and grasshoppers, but you can use any familiar animals. Choose a small number of hawks (1 or 2), more mice (4 to 10), and lots of grasshoppers. Use armbands, signs, or other markers to identify the different kinds of animals. The facilitator places the colored necklaces in sight around the area where the game will be played.
- The facilitator announces that the colored necklaces are food for grasshoppers. What she doesn’t say is that the red beads are toxic chemicals that have collected in the food. The grasshoppers collect their food by putting necklaces around their necks. Each grasshopper collects as much food as possible, remembering how many necklaces she collected in total.
- Next, release the mice into the play area to hunt the grasshoppers. Whenever a mouse catches a grasshopper, he or she puts on all the necklaces the grasshopper was wearing and the grasshopper leaves the game. Each mouse should have time to catch one or more grasshoppers and put on the necklaces he collects.
- Release the hawks into the game to hunt the mice, while the mice are hunting grasshoppers. Any mouse caught by a hawk turns over all of its necklaces and then sits out.
- Once the hawks have collected all the necklaces, all the players gather in a circle. Ask each grasshopper and mouse how many necklaces they collected before they were eaten and if any of these necklaces had red beads on them. Then ask the hawks to show the necklaces they collected.
- Begin a discussion, telling the group that the red beads are toxic chemicals in the food. Explain that the hawk with the most red beads dies because the most toxics have accumulated in her body. Other hawks may survive, but will lay eggs with thin shells or hatch sickly chicks. Ask the group to discuss how toxic chemicals get into their water or food. What foods do people eat that may have toxic chemicals in them? How can we keep toxic chemicals from accumulating in our bodies? How can we keep them out of the environment?