Commentary

Why Are Chemicals in My Body?

By: Ronald D. Hood, Ph.D.
Professor Emeritus
The University of Alabama
Principal, Ronald D. Hood & Associates
Toxicology Consultants

Why are chemicals in my body?

Environmental chemicals are present in our bodies because we eat, drink, breathe, and live in the modern world - with all its advantages, including the longer, healthier lives we live. We have recently become more aware of these chemicals because of the rapid development of analytical technology that allows us to detect lower and lower levels of more and more substances. It is this new knowledge that has led to increased concern about whether the presence of such substances is causing us harm.

Are environmental chemicals bad for me?

To better understand the implications of the presence of these chemicals, we first must understand that the entire universe as we know it is made up of chemical substances -- our solar system, the Earth, the air we breathe, and all living creatures are made up of chemicals. Thus, the notion that all chemicals are invariably harmful is quite inaccurate and misleading. Rather, both naturally occurring and manufactured chemicals can be harmful to humans depending on the amounts present. Chemicals not naturally found in our bodies may be referred to as "environmental chemicals". In the CDC's Second National Report on Human Exposure to Environmental Chemicals an "environmental chemical" is defined as "a chemical compound or chemical element present in air, water, food, soil, dust, or other environmental media (e.g., consumer products)." Environmental chemicals present in the body may also be referred to as "xenobiotics," meaning chemical substances that are foreign to the biological system. These substances may be innocuous, harmful, or of unknown toxicity.

How do environmental chemicals enter my body?

There are three major exposure routes by which environmental chemicals can enter the body. These routes are:

Oral - We take in chemicals of many kinds, both wanted (such as those naturally found in food, drink, and those that make up synthetic medications) and unwanted (such as foreign chemicals found in what we eat and drink). Ingested soil and dust are other sources of foreign chemicals, especially for children.

Inhalation - As we breathe, we may inhale natural and foreign chemicals in gases, dust, smoke, aerosols, or vapors.

Dermal - Natural and foreign substances present in the environment may also be absorbed through contact with the skin.

How long will environmental chemicals remain in my body?

Some chemicals or their breakdown products (metabolites) remain in our bodies for only a short time before being excreted, usually via urine or bile, although continuous exposure to such chemicals can create a "persistent" presence. Other chemicals are not readily excreted following exposure and can remain in the body for long periods, especially in certain tissues, such as adipose (fat) tissue and bone. For example, chlorinated pesticides, such as DDT, which are no longer used in many countries can still be widely found in humans because they or their metabolites can remain in the body for many years following exposure.

Can I find out about environmental chemicals in my own body?

In general, the tests required to assess the kinds and amounts of environmental chemicals in your body are complex, expensive and not commonly available. Government agencies, health care facilities, or other laboratories do not routinely offer biomonitoring measurements. Most of what we know about exposure to chemicals comes from limited studies of a few compounds, conducted by government agencies on selected groups of people. And of course biomonitoring only measures exposure; it does not provide information about toxicity or risk from the presence of such substances.