Plants 2,3,7,8-TCDD

Treated effluents from various Ontario pulp and paper plants using either the bleached kraft (8 mills) or sulfite bleaching process (2 mills) were analyzed for CDDs (Clement et al. 1989). 2,3,7,8-TCDD was not detected in any of the effluent samples with detection limits ranging from 0.07 to 0.7 ppt. A few samples contained a TCDD isomer (not 2,3,7,8-TCDD) at concentrations ranging from 0.06 to 0.12 ppt. PeCDD (0.07 ppt) was detected in one effluent sample, and OCDD (0.05-0.79 ppt) was detected in 4 effluent samples. Suspended particulates were collected from the final effluent from two plants. 2,3,7,8-TCDD and OCDD were detected in the particulates at a concentration range of 200-660 ppt and 180-210 ppt, respectively. The concentration of 2,3,7,8-TCDD determined in the particulates represents levels in the final effluent of 5-10 ppq, suggesting that 2,3,7,8-TCDD is associated with suspended particulate materials in the effluents (Clement et al. 1989). 

Plot Plant Wt. g Plant TCDD ppb Rinse TCDD (1) ppb Total Plant ppb Sample Date Day Mon Yr ... 

Plot Plant TCDD Soil TCDD Concentration Sample Date... 

In the United States, the Clean Air Act of 1990 requires plants to reduce emissions of 189 toxic and carcinogenic substances such as chlorine, chloroform, and 2,3,7,8-TCDD (dioxin) by 90% over the 1990s. The U.S. Environmental Protection Agency is working to develop standards based on maximum achievable control technologies and the industry has invested bUHons of doUars in capital investments to retrofit or rebuUd plant equipment to meet these measures. 

The plant s product was hexachlorophene, a bactericide, with trichlorophenol produced ns an intermediate. During normal operation, a very small amount of TCDD (2,3,7,8 telrachlomdib zoparadioxin) is produced in the reactor as an undesirable side product. TCDD is perhaps the most ]in(enl toxin known to man. Studies have shown TCDD to be fatal in doses as small as lE-9 times die body weight, it insolubility in water makes decontamination very difficult. Nonlethal doses of TCDD result in chloracne, an acne-like disea.se that can persist for several years. 

A similar rclea.se occurred in Duphar, India in 1963, after which the plant was disassembled brick by brick, encased in concrete and dumped into the ocean. Less than 200 grams of TCDD w ere released at Duphar, and the contamination was confined to the plant. Fifty men did the clean nn four eventually died from the exposure. 

An environmental protocol has been developed to assess the significance of newly discovered hazardous substances that might enter soil, water, and the food chain. Using established laboratory procedures and C-labeled 2,3,7,8-tetra-chlorodibenzo-p-dioxin (TCDD), gas chromatography, and mass spectrometry, we determined mobility of TCDD by soil TLC in five soils, rate and amount of plant uptake in oats and soybeans, photodecomposition rate and nature of the products, persistence in two soils at 1,10, and 100 ppm, and metabolism rate in soils. We found that TCDD is immobile in soils, not readily taken up by plants, subject to photodecomposition, persistent in soils, and slowly degraded in soils to polar metabolites. Subsequent studies revealed that the environmental contamination by TCDD is extremely small and not detectable in biological samples. 

TAetection of the highly potent impurity, 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) in the herbicide 2,4,5-trichlorophenoxyacetic acid (2,4,5-T), necessitated an environmental assessment of the impact of this contaminate. Information was rapidly needed on movement, persistence, and plant uptake to determine whether low concentrations reaching plants, soils, and water posed any threat to man and his environment. Because of the extreme toxicity of TCDD, utmost precautions were taken to reduce or minimize the risk of exposure to laboratory personnel. Synthesis of uniformly labeled C-TCDD by Muelder and Shadoff (I) greatly facilitated TCDD detection in soil and plant experiments. For unlabeled experiments it seemed wise to use only small quantities of diluted solutions in situations where decontamination was feasible and to rely on the sensitivity afforded by electron capture gas chromatography... 

Plant uptake is one of several routes by which an organic contaminant can enter man s food chain. The amount of uptake depends on plant species, concentration, depth of placement, soil type, temperature, moisture, and many other parameters. Translocation of the absorbed material into various plant parts will determine the degree of man s exposure—i.e., whether the material moves to an edible portion of the plant. Past experience with nonpolar chlorinated pesticides suggested optimal uptake conditions are achieved when the chemical is placed in a soil with low adsorptive capacity e.g., a sand), evenly distributed throughout the soil profile, and with oil producing plants. Plant experiments were conducted with one set of parameters that would be optimal for uptake and translocation. The uptake of two dioxins and one phenol (2,4-dichlorophenol (DCP)) from one soil was measured in soybean and oats (7). The application rates were DCP = 0.07 ppm, DCDD 0.10 ppm, and TCDD = 0.06 ppm. The specific activity of the com-... 

Next, we attempted to deal with translocation of foliar-applied TCDD. Labeled dioxins were applied to the center leaflet of the first trifoliate leaf of 3-week-old soybean plants and the first leaf blade of 12-day-old oat plants. All compounds were applied in an aqueous surfactant solution (Tween 80) to enhance leaf adsorption and to keep the water insoluble dioxins in solution. Plants were harvested 2, 7, 14, and 21 days after treatment, dissected into treated and untreated parts, and analyzed separately. Neither dioxin nor chlorophenol was translocated from the treated leaf. A rapid loss of the dichlorodioxin and dichlorophenol occurred from the leaf surface. This loss may have resulted from volatilization. Very little TCDD was lost from soybean leaves while a gradual loss (38% in 21 days) did occur from oat leaves. 

Several facts have emerged from our studies with 2,7-DCDD and 2,3,7,8-TCDD. They are not biosynthesized by condensation of chloro-phenols in soils, and they are not photoproducts of 2,4-dichlorophenol. They do not leach into the soil profile and consequently pose no threat to groundwater, and they are not taken up by plants from minute residues likely to occur in soils. Photodecomposition is insignificant on dry soil surfaces but is probably important in water. Dichlorodibenzo-p-dioxin is lost by volatilization, but TCDD is probably involatile. These compounds are not translocated within the plant from foliar application, and they are degraded in the soil. 

Mutagenic responses were produced in Escherichia coli and certain strains of Salmonella typhimurium bacteria by 2,3,7,8-TCDD, but not by octa-CDD (Vos 1978). Further, chromosomal aberrations were induced in at least one species of higher plant and mammal (Ramel 1978). It must be concluded at this time that 2,3,7,8-TCDD is mutagenic or has mutagenic potential. 

A plant manufacturing 2,4,5-trichlorophenol in Seveso, Italy exploded and liberated substantial amounts of TCDD (dioxin). Although it caused quite a scare and the town was evacuated, there were no known deaths and no increase in birth defects reported. Some chloracne (a skin disease) occurred and one liver cancer was diagnosed. 

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... 

Depending upon the circumstance and desired effects, endocrine-disrupting chemicals can be either good or bad. The endocrine system is a finely balanced system responsible for fertility and many of the feminine and masculine traits we are all familiar with. Endocrine disruptors are used by millions of women in the form of the pill to control fertility. Chemicals in birth control pills subtly manipulate the endocrine system to reduce fertility. Unfortunately, we now know that many chemicals are capable of influencing the endocrine systems. When these chemicals, such as DDT and TCDD, are released into the environment, they reduce the fertility of wildlife. Exposure to endocrine disruptors is linked to decreased fertility in shellfish, fish, birds, and mammals. Endocrine disruptors such as nonylphenol have been shown to feminize male fish, interfering with reproduction. Some studies have also linked exposure to endocrine disruptors to decreases in human male sperm count. Ironically, urinary metabolites of the birth control pill as well as the female hormone estrogen pass through waste treatment plants and are released into the aquatic environment, where even small concentrations cause feminization of male fish. 

Facchetti, S., Balasso, C., Fichtner, G., Frare, A., Leoni, A., Mauri, C., Vasconi, M. (1986) Studies on the absorption of TCDD by some plant species. Chemosphere 15(9-12), 1387-1388. 

In the pure form, CDDs are colorless solids or crystals. CDDs enter the environment as mixtures containing a variety of individual components and impurities. In the environment they tend to be associated with ash, soil, or any surface with a high organic content, such as plant leaves. In air and water, a portion of the CDDs may be found in the vapor or dissolved state, depending on the amount of particulate matter, temperature, and other environmental factors. 2,3,7,8-TCDD is odorless. The odors of the other CDDs are not known. CDDs are known to occur naturally, and are also produced by human activities. They are naturally produced from the incomplete combustion of organic material by forest fires or volcanic activity. CDDs are not intentionally manufactured by industry, except in small amounts for research purposes. They are unintentionally produced by industrial, municipal, and domestic incineration and combustion processes. Currently, it is believed that CDD emissions associated with human incineration and combustion activities are the predominant environmental source. 

TCDD levels were measured in the workers at two of the plants. The mean 2,3,7,8-TCDD serum lipid level in 281 production workers in the Newark, New Jersey, and Verona, Missouri, plants was... 

Residential/Environmental Exposures. Several incidents in which populations were exposed to potentially high levels of 2,3,7,8-TCDD include an industrial accident that occurred during the production of 2,4,5-TCP at the ICMESA plant in Seveso, Italy and the spraying of roads and other places... 

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... 

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