2,4-D Dioxin Contamination 

2apr01

EXTOXNET Extension Toxicology Network
http://pmep.cce.cornell.edu/profiles/extoxnet/24d-captan/24d-ext.html

Although recently manufactured 2,4-D technical acids have consistently been free of dioxin contamination, the amine and ester products may have measurable levels of some forms of dioxin. According to a study of 2,4-D manufactured in Canada*, of 26 amine samples tested, 8 were positive. The levels ranged from 5 ppb to nearly 500 ppb. Several different forms of dioxin were present in the different products. All but one of 21 ester samples were positive.

Since an earlier study had reported finding hexachlorodioxin in 2,4-D the samples were analyzed for mono- to octachlorodioxin but no other isomers were found above the detection limit of 10 ppb. A subsequent study of 2,4-D manufactured in the United States found very little dioxin contamination. Measurable amounts of one form of the compound (2,7 DCDD) were found in 3 of 30 samples, with traces of other isomers. The amounts found do not have biological significance.

* U. S. Environmental Protection Agency (1987). Health Advisory, Office of Drinking Water

Environmental Health Perspectives 3mar01
http://ehpnet1.niehs.nih.gov/docs/2001/109-3/niehsnews.html

What Is Agent Orange?

During Operation Ranch Hand, which lasted from 1962 to the early days of 1971, some 19 million gallons of herbicide was sprayed on Vietnamese and Laotian lands to remove the forest cover that shielded the Viet Cong and to destroy crops. Various formulations were used; most were mixtures of the phenoxy herbicides 2,4-D and 2,4,5-T. The different formulations were named according to the color-coded drums they were shipped in; the most widely used--and perhaps the best remembered--was Agent Orange, composed of equal parts 2,4-D and 2,4,5-T. Today, the term "Agent Orange" is used as a catchall phrase to describe all of these compounds.

These herbicides were contaminated with minute amounts of 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD, also known as dioxin), a by-product of the manufacturing process for 2,4,5-T. TCDD has a half-life of 8.7 years in humans. It is a persistent organic pollutant; after 25 years since the end of the Vietnam War, a quarter of the TCDD released through herbicide spraying is still in the Vietnamese environment. TCDD has been found to be biologically active at minuscule concentrations. The EPA currently regulates TCDD in drinking water at a concentration of 13 parts per quintillion. (The agency is currently reassessing this regulation, with a report due in early 2001.

TCDD has been shown to suppress the immune system in animals, and has caused cleft palate and ureter defects in mice. Rats exposed to TCDD have shown hormonal imbalances, which may affect the development and function of the endocrine system. TCDD is also believed to cause cancers such as Hodgkin disease and soft-tissue sarcoma, liver damage, reproductive problems such as spina bifida and miscarriage, neurotoxicity, and skin effects such as chloracne, which causes severe acne-like lesions. In January 2001, the National Toxicology Program published an addendum to the Report on Carcinogens, Ninth Edition, listing TCDD as a known human carcinogen.

More on dioxin in EHP same issue as above http://ehis.niehs.nih.gov/topic/dioxin.html

EPA IRIS website on 2,4-D http://www.epa.gov/ngispgm3/iris/subst/0150.htm  this is only interesting Take a look at (last) section VIII. SYNONYMS