Smarter Living: Chemical Index

Dioxins are long-lived toxic chemicals that have invaded every living creature in every region of the world.

Health Concerns

The term "dioxins" refers to a family of chemicals that contain one or more chlorine atoms attached to a double ring of carbon atoms. The most toxic of the dioxins goes by the abbreviation 2,3,7,8-TCDD, short for 2,3,7,8-tetrachlorodibenzo-p-dioxin. High levels can cause liver damage and a host of problems, most visibly including a skin condition called chloracne. However, animal and human studies show that even very low levels of 2,3,7,8-TCDD (levels many people contain in their bodies today) can cause a variety of health problems, including immunologic impairments, hormonal alterations, and cancer. The hormone alterations and immune dysfunction increase risks of reduced fertility, birth defects, and cancer. For example, animal studies have found that the chemical can reduce sperm production, alter sex hormone levels, and increase miscarriage rates.

The chemical can also cause birth defects such as skeletal deformities, kidney defects, and learning and behavioral problems. More recent studies have found a potential link to increased diabetes risk. The International Agency for Research on Cancer (IARC) has determined that 2,3,7,8-TCDD can cause cancer in people, and the federal National Toxicology Program has placed it on its list of chemicals “known to be a human carcinogen.”


Some dioxin-like chemicals can be produced naturally from volcanic activity or forest fires, but by far the predominant source is human activity, such as the burning of fossil fuels and the incineration of household and industrial garbage, especially garbage that contains polyvinyl chloride (PVC) plastic, bleached paper, or materials previously treated with chlorinated pesticides or preservatives, and polychlorinated biphenyls (PCBs). Cigarette smoke and diesel exhaust also contain small amounts of dioxins.

Dioxins are also formed during the industrial bleaching of paper products and the manufacture of certain chlorine-containing chemicals and pesticides. For example, dioxins were found to contaminate the herbicides in the defoliant Agent Orange used during the Vietnam War. Although regulations on incineration and paper bleaching, as well as bans on PCBs and certain chlorine-containing pesticides have reduced dioxin emissions, , the environmental contamination remains. Dioxins are extremely long lived and are part of a group of chemicals that the EPA calls persistent organic pollutants (POPs). These chemicals can travel long distances in the air and are found in every part of the world, including the Arctic and Antarctic.

The historical pollution of soil and water has resulted in dioxins working their way into the food chain, and indeed the most common route of human exposure is from food. Dioxins that settle into a water body such as a lake can be ingested by small aquatic organisms, which are then eaten by small fish that are then eaten by larger fish, and in this way they work their way up the food chain into fish species commonly eaten by humans. Dioxins that settle on land can cling to soil particles and be taken up into plants that are then used as animal feed. In fact, according to the EPA, almost every living creature has been exposed to dioxins.

Because dioxins accumulate in fat, the foods that contain the highest amounts are meat, dairy products, and fish. Dioxins become concentrated in human milk, although the benefits of breastfeeding far outweigh the concern from dioxin. Because dioxins tend to cling to soil, drinking water is not a major source of exposure.

All people have some level of dioxin stored in their body fat, according to a representative sampling of people in the U.S. conducted by the U.S. Centers for Disease Control and Prevention (CDC). It takes 7 to 12 years to excrete half of the 2,3,7,8-TCDD, so clearing the body of the chemical takes a long time and most of us are being continually re-exposed through our diets.

Stay Safe

To reduce your exposure to dioxins, first make sure that you have no immediate exposures such as smoking or living near a dioxin-contaminated site. Next, tackle your diet, reducing your intake of fatty meats and dairy products in favor of healthy choices such as lean meats, low-fat dairy products, fruits, vegetables and whole grain products. Some types of seafood are more likely to contain dioxins than others. You can find healthier seafood choices at NRDC's Sustainable Seafood Guide
or at SeafoodWATCH, a project of the Monterey Bay Aquarium and the Environmental Working Group.
If you do your own fishing, pay attention to local fishing advisories. Although dioxins can be found in breast milk, the benefits of nursing for a baby's health far outweigh the risk of harm from dioxins.

last revised 12/27/2011

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