Dioxin
Dioxin refers to a group of toxic chemical compounds, with the most notorious being 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD). Produced as a by-product in various industrial processes, dioxin has raised significant environmental and health concerns due to its extreme toxicity, even at very low exposure levels. Notably, dioxin exposure can lead to serious health issues, including chloracne, immune system damage, and potential links to several types of cancer. Historically, significant exposure incidents, such as the use of Agent Orange during the Vietnam War and the Seveso disaster in Italy, have highlighted dioxin's harmful effects.
Dioxin remains persistent in the environment, capable of lingering for years in soil and sediments. While regulatory efforts have reduced dioxin emissions in the United States, there are ongoing concerns about its role as an endocrine disruptor, affecting hormonal functions in humans and wildlife. Research into dioxin has revealed variable effects across different species and individual organisms, complicating its assessment and regulation. Understanding dioxin’s impact continues to evolve, raising important questions about environmental safety and public health.
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Dioxin
DEFINITION: Toxic chemical that is a by-product of certain manufacturing processes
Dioxin has become an environmental concern because exposure to the chemical, even in trace amounts, can cause severe health problems in humans and other organisms.
Approximately seventy-five different types of dioxins exist, but the term “dioxin” is commonly used to refer to a variety known as 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a highly toxic chemical that has caused great concern among environmentalists. Dioxin can be destroyed by exposure to direct sunlight in the presence of hydrogen, but the chemical can remain under the surface of the ground for ten years or longer.
One of the earliest documented cases of dioxin exposure occurred in West Germany in 1957, when thirty-one workers at a chemical plant developed chloracne, a skin disease that is one of the characteristic effects of exposure. In 1977 investigators in the Netherlands discovered dioxin in fly ash from a municipal incinerator. By 1980 scientists had determined that dioxin is produced when practically any organic substance is burned.
At first it was thought that chloracne was the only effect of exposure to dioxin. As time went on, however, experiments with animals revealed that dioxin is highly toxic. Researchers found that guinea pigs could be killed by as little as 1 microgram of dioxin per kilogram of body weight, but hamsters could take a dose of 5,000 micrograms per kilogram. Further experimentation showed that the organs within different animals were also affected differently by the chemical. Such differences among animal species and organs had never been found with any previously tested substance, and they invalidated the usual methods used in testing on animals. Because of this, dioxin became known as the first environmental hormone. That is, it acts like a hormone in animals and plants in that it has strange effects on various organs.
Scientists also began to suspect that dioxin could be involved in causing various cancers. The most famous exposure incident occurred between January 1965 and April 1970, when the US military used the defoliant Agent Orange during the Vietnam War to kill trees and plants that provided hiding places and food for North Vietnamese soldiers. One of the herbicides used was contaminated with dioxin during the manufacturing process. After the war, the National Academy of Sciences reviewed more than six thousand studies of dioxin exposure and came to the conclusion that four kinds of cancer could be linked to the chemical.
Other studies of dioxin exposure have produced mixed results. Thirty-seven thousand people were exposed to dioxin in Seveso, Italy, in 1976 after a factory explosion. Although no immediate human fatalities were traceable to the accident, a significant number of male births in the region were interrupted before term during the four months following exposure. Dioxin was therefore suspected of being a factor in the decline of male births worldwide. Two hundred workers were exposed to dioxin in 1949 at Nitro, West Virginia, and several died from cancer. Sweden reported six times the normal cancer rate in people exposed to dioxin, but Finland traced nineteen hundred cases of exposure and found no harmful effects. A Veterans Administration study of eighty-five thousand Vietnam veterans found lower-than-normal rates of cancer. Many researchers have explained such disparate findings by noting that dioxin does not seem to cause cancer itself; rather, it acts as an influence on other cancer-causing chemicals.
Another well-publicized dioxin incident occurred in 1983 in Times Beach, Missouri, when a local resident tried to settle the dust on the town’s roads by wetting the roads with a spray of recycled oil that was unknowingly contaminated with dioxin. The federal government bought the entire town and moved everyone out to prevent any further exposure to the chemical, even though at the time it was not known that dioxin could cause any of the cancers later linked to exposure.
In a September 1994, report, the Environmental Protection Agency (EPA) stated that perhaps no more than 14 kilograms (30 pounds) of dioxin are released into the US environment annually. Even this trace amount is unacceptable, however, given that dioxin is suspected of being an endocrine disrupter, which means that trace amounts can disrupt the effects of other hormones and cause numerous disorders. However, later EPA reports indicated the amount of dioxin being released has decreased by 11 percent from 2013 to 2022 and by 23 percent from 2021 to 2022.
According to the 1994 EPA report, a dioxin may be responsible for damaging immune systems and creating other hormone-related diseases, such as diabetes. For example, mice treated with dioxin readily die after exposure to viruses that ordinarily would have no effect on them.
Scientific investigation of dioxin has expanded the view of environmental chemicals to include environmental hormones and hormone disrupters. These seventy or more substances are like no other chemicals known in the past, raising the critical question of how they are to be regulated when so little is known about their effects. All previous ways of measuring are invalid because these substances do not have uniform effects. One animal is killed by a tiny exposure and another is seemingly unharmed, while both may have internal effects that remain undiscovered.
Bibliography
"Dioxins." World Health Organization (WHO), 29 Nov. 2023, www.who.int/news-room/fact-sheets/detail/dioxins-and-their-effects-on-human-health. Accessed 16 July 2024.
Friis, Robert H. “Pesticides and Other Organic Chemicals.” Essentials of Environmental Health. Jones, 2007.
Little, Jean. "A Town, a Food, and Superfund: Looking Back at the Times Beach Disaster Nearly Forty Years Later." Environmental Protection Agency (EPA), 24 Nov. 2023, www.epa.gov/mo/town-flood-and-superfund-looking-back-times-beach-disaster-nearly-40-years-later. Accessed 16 July 2024.
Schecter, Arnold, and Thomas Gasiewicz, eds. Dioxins and Health. 2nd ed. Taylor, 2002.
Young, Alvin Lee. The History, Use, Disposition, and Environmental Fate of Agent Orange. Springer, 2009.