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Bioaccumulation & Biomagnification


  • Phthalates do not bioaccumulate. That is, they do not build up in the body. Humans break them down quickly and dispose of them within 12 to 24 hours.
  • Phthalates do not biomagnify in the food chain. That is, they do not build up in the bodies of fish or animals that larger animals or humans ingest.

Background

Substances encountered in the environment can find their way into plants and animals, and into humans. Most of what finds its way into us, from eating, drinking, breathing, even touching, finds its way out again. That is, we break down some of these substances and excrete or exhale them. But some substances are not broken down or excreted so readily. These substances can build up and are usually stored in fatty tissue. This process is known as bioaccumulation. As the concentrations increase, a health risk could arise no matter whether the substance is "foreign" to the body (like lead or mercury) or whether it is needed by the body at lower concentrations (like vitamins or trace elements, e.g., selenium).

A related process called biomagnification is also very relevant to human health. It involves how materials may increase with increasing levels in the food chain. If a small fish bioaccumulates a substance, and a bigger fish eats the smaller fish and, if both fish are incapable of metabolizing the substance, then the substance could magnify in concentration within each higher organism. Organisms at the top of the food chain, like the large fish in this example, or humans could face a risk if the substance is harmful and if enough of the substance accumulates in the organism’s tissues.

The Issue

The Centers for Disease Control and Prevention (CDC) has undertaken a program to analyze human blood and urine, looking for hundreds of different substances. The CDC's third National Exposure Report, issued in January 2005, showed that the "breakdown" products (also known as metabolites) of some phthalates were found in most of the samples. (The full CDC report may be found at http://www.cdc.gov/exposurereport/). Some have incorrectly concluded that the presence of these metabolites in these samples means that phthalates will continually build up in the body.

The Evidence

Phthalate exposures indicated by the CDC measurements were far below the safety levels set by the Environmental Protection Agency (EPA). Other studies have shown that phthalates are readily broken down by biological organisms such as fish and mammals. For humans this occurs within 12 to 24 hours. Thus, phthalates do not pose a bioaccumulative concern, nor do they biomagnify in food chains.

Panel statements on both CDC exposure reports may be found in the Media Center section (2001, 2003).

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