TCDD contamination

The study site, consisting of about 11 contaminated acres belonging to eight property owners, is in a small community midway between Verona and St. Louis, Missouri. Records indicate that on May 20, 1971, a truck driven by an employee of a salvage waste oil company was ticketed for being 950 pounds overweight. The truck was en route from Verona to St. Louis with a load of TCDD-contaminated still... 

No adverse effects expected in woodcocks after consuming earthworms and insects from 2,3,7,8-TCDD-contaminated soils <50 ng/kg FW soil 12... 

In October 1973, soil samples collected from Grids I and II were analyzed and found to contain significant levels of TCDD. Highest TCDD residues (740-1,500 parts per trillion, ppt) were found on Grid I, the area sprayed with Herbicide Purple In 1962-1964. Subsequent soil samples confirmed TCDD contamination throughout three of the four test grids. The persistence of TCDD In the soils of Test Area C-52A has recently been described by Young, 1983 ( 4). 

I am indebted to Drs. Eugene Arnold and Mason Hughes for the analyses of the phenoxy herbicides, phenols and the TCDD contaminant. 

Herbicides are designed to kill plants, not animals, and in general have lower mammalian toxicity than insecticides. Most herbicides interfere with plant hormones or enzymes that do not have any direct counterpart in animals. The most serious human health concerns have been related to contaminants of the primary chemical herbicide. There is an enormous amount of animal and some human toxicity data on 2,4-D and 2,4,5-T, but it now appears that much of this toxicity is caused by the contaminant TCDD. Military personnel exposed to Agent Orange, often contaminated with TCDD, reported birth defects, cancers, liver disease, and other illness. These concerns led to improvement in the manufacturing process to reduce TCDD contamination and ultimately to a reduction in use of 2,4-D herbicides. There is also concern that some herbicides may affect wildlife. For example, atrazine, a persistent herbicide, may adversely affect frogs. Persistence of herbicides may also... 

The presence of TCDD in 2,4,5-T is believed to be largely responsible for other human toxicities associated with the herbicide. There is epidemiologic evidence indicating an association between occupational exposure to the phenoxy herbicides and an excess incidence of non-Flodgkin s lymphoma. The TCDD contaminant in these herbicides seems to play a role in a number of cancers such as soft tissue sarcomas, lung cancer, Flodgkin s lymphomas, and others. 

P. Mastroiacovo et al., Birth Defects in the Seveso Area After TCDD Contamination, JAMA259 (1988) 1668-1972. 

Reggiani G. Medical problems raised by the TCDD contamination in Seveso, Italy. Arch Toxicol 1978 40 161-188. 

Some of the most comprehensive studies on occupational exposure were conducted by the National Institute for Occupational Safety and Health (NIOSH). They are cross-sectional studies of workers at U.S. chemical facilities involved in the manufacture of 2,3,7,8-TCDD-contaminated products between 1942 and 1984 (Calvert et al. 1991, 1992 Egeland et al. 1994 Fingerhut et al. 1991 Sweeney et al. 1993). Serum... 

TCDD exposure was assumed if the worker was exposed to a phenoxy herbicide known to be contaminated with 2,3,7,8-TCDD, such as 2,4,5-T. However, the level of exposure to these 2,3,7,8-TCDD-contaminated products was generally not determined. 

Various populations in Missouri were exposed to 2,3,7,8-TCDD in 1971 and 1972 as a result of spraying approximately 29 kg of 2,3,7,8-TCDD-contaminated waste oil on horse arenas, parking lots, and residential roads for dust control (Andrews et al. 1989). The oils originated from an industrial waste residue contaminated with 2,3,7,8-TCDD at levels of 305 ppm (Needham et al. 1991). An exposed group of 51 adults have been the subject of several studies. Adipose tissue levels, as well as paired human serum levels, were measured for 36 of these persons. Sixteen of the individuals were residents of areas where roadways had been sprayed and had mean 2,3,7,8-TCDD adipose tissue levels of 21.1 ppt (range,... 

No respiratory effects were associated with exposure to 2,3,7,8-TCDD-contaminated herbicides in a group of Vietnam Air Force veterans involved in Operation Ranch Hand examined more than 10 years after the war (Wolfe et al. 1985). In the 1987 follow-up (USAF 1991), no association was found between the initial or current serum level of 2,3,7,8-TCDD and incidences of asthma, bronchitis, pleurisy, pneumonia, or tuberculosis abnormal spirometric measurements were often associated with CDD blood levels, but according to the authors (USAF 1991), the differences in the mean level between high- and low-exposure subjects were not clinically important. The authors suggested that these findings may have been related to the association between 2,3,7,8-TCDD and body fat because obesity is known to cause a reduction in vital capacity. 

No cardiovascular effects were observed in a group of Air Force veterans exposed to 2,3,7,8-TCDD-contaminated herbicides during the Vietnam war and examined several years post-exposure (Wolfe et al. 1985). However, a follow-up study of the Ranch Hand cohort reported increased mean diastolic blood pressure in those with current serum lipid 2,3,7,8-TCDD levels from 15 to 33.3 ppt, but not in subjects with higher 2,3,7,8-TCDD serum levels (USAF 1991). In addition, the proportion of abnormally low peripheral pulses in all Ranch Hand veterans, regardless of serum levels, was elevated relative to a comparison group. Also, arrhythmias detected on the electrocardiogram were significantly associated with 2,3,7,8-TCDD exposure, but there was no consistent dose-response relationship. 

Gastrointestinal Effects. Earlier studies of individuals with exposure to substances contaminated with 2,3,7,8-TCDD found significant elevations in self-reported ulcers (Bond et al. 1983 Suskind and Hertzberg 1984), but a study of Vietnam veterans (USAF 1991) failed to find such effects. A more recent study evaluated the gastrointestinal effects of exposure to substances contaminated with 2,3,7,8-TCDD in an occupational cohort (Calvert et al. 1992). More than 15 years earlier, the workers were employed in the manufacture of trichlorophenol and its derivatives at 2 chemical plants. A total of 281 workers participated in the medical study the control group consisted of 260 unexposed subjects who lived in the same communities as the workers. The participants underwent a comprehensive physical examination of the abdomen and rectum. The mean serum 2,3,7,8-TCDD level (on a lipid basis) for the workers was 220 ppt and was found to be highly correlated with years of exposure to 2,3,7,8-TCDD-contaminated substances controls had a mean serum 2,3,7,8-TCDD concentration of 7 ppt. At the time of examination, the workers were not found to be at increased risk for any gastrointestinal diseases. Moreover, neither... 

Hematological Effects. Human studies regarding exposure to 2,3,7,8-TCDD or 2,3,7,8-TCDD-contaminated chemicals did not find any overt hematological effects after intermediate- (Wolfe et al. 1985) and chronic-duration exposures (Stehr et al. 1986). 

TCDD contaminated herbicides as compared to a group of Ho Chi Minh City residents presumably never exposed to 2,3,7,8-TCDD-contaminated herbicides. In contrast, a case-control study by Ha et al. (1996) did not find a significant association between exposure to 2,3,7,8-TCDD-contaminated herbicides and the occurrence of complete hydatidiform mole or choriocarcinoma among women living in southern Vietnam. 

TCDD or 2,3,7,8-TCDD-contaminated chemicals, workers involved in manufacturing or application of phenoxy herbicides and/or chlorophenols, and Vietnam veterans. In most of the human studies, exposure was poorly characterized. 

TCDD-contaminated chemicals found no association between 2,3,7,8-TCDD exposure (body burden) and gastrointestinal disease (Calvert et al. 1992). 

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