Concentration, 2,3,7,8-TCDD plants

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-... 

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. 

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... 

Corbet et al. (1983) reported that a rooted plant species (Potemagetonpectimatus) and a surface-dwelling duckweed (Lemna sp.) accumulated concentrations of 1,3,6,8-TCDD of 280 and 105 ng/g (dry weight), respectively, following exposure to water containing 1,000 ng/L (ppt). The maximum concentrations were observed 8 days post-application and represented 6% of the total TCDD applied. These results are similar to those reported by Tsushimoto et al. (1982) in an outdoor pond study, in which a maximum bioaccumulation of 2,3,7,8-TCDD in the pond weeds Elodea nuttali and Ceratophyllon demersum equivalent to a BCF of 130 occurred after 5 days of exposure. In both studies, the tissue concentrations reached equilibrium in approximately 20 days and remained constant until the end of the experiment (approximately 58 and 170 days, respectively). These experimental data indicate that CDDs can accumulation in aquatic plant species through waterborne exposure. 

TCDD. A maximum of 0.15% (0.12 ppm) of 2,3,7,8-TCDD present in soils was translocated to the aerial portion of the oat and soybean plants. No detectable amounts of the compound were found in the oat or soybean plants harvested at maturity. The amount of 2,3,7,8-TCDD applied to these soils was many thousands of times greater than that which would occur in soils from herbicide applications containing a few ppm of 2,3,7,8-TCDD as an impurity. Even upon exposure to these high concentrations... 

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). 

In 1983, Jobb et al. (1990) conducted a survey of 49 drinking water supplies in Ontario, Canada, including supplies in the vicinity of chemical plants and pulp and paper mills. OCDD was detected in 36 of 37 positive samples ranging from concentrations of 9 to 175 ppq in raw samples (33 positive samples) and from 19 to 46 ppq in treated (filtered) water samples (4 positive samples). These low concentrations were found primarily in water obtained downstream of industrial areas in the St. Clair/Detroit River system. Concentrations of 2,3,7,8-TCDD were not detected in any sample. Because CDDs are hydrophobic, concentrations of these compounds in water tend to be adsorbed onto particulate matter in water. Conventional water treatment processes are expected to be effective in removing the CDDs along with the particulates. This is substantiated by the fact that only 4 of the 37 positive detections were found in treated drinking water, while 33 detections were found in raw water samples. 

An occupational study of workers exposed to CDDs at a Missouri chemical plant from 1968 to 1972 found a mean 2,3,7,8-TCDD concentration of 390 ppt in the adipose tissue of 4 exposed workers measured 13-17 years post-exposure. The chemical plant made 2,4,5-trichlorophenol (2,4,5-TCP), which was used as a feedstock to produce butyl esters of 2,4,5-trichlorophenoxyacetic acid (2,4,5-T esters) and hexachlorophene between 1968 and 1972. The 2,3,7,8-TCDD was generated as an... 

A number of combustion and chemical production processes contribute to environmental concentrations of PCDD/F. Sources that have traditionally caused the greatest concern include municipal waste incinerators, hospital waste incinerators, bleached chemical wood pulp and paper mills, motor vehicles and wood combustion. We have attempted to represent the most recent data available on PCDD/F emissions from these sources. It should be remembered that the list presented here is by no means exhaustive. Potential sources of TCDD not discussed in the following paragraphs include discharges from metal processing and treatment plants, copper smelting plants and pentachlorophenol production. 

The fate of 2,3,7,8-tetrachlorobenzo[l,4]dioxin (TCDD) was examined in freshwater ponds using 14C-labeled substrate over a period of up to 2 years. Equilibrium concentrations in pondweeds (Elodea nuttali and Cerotophyllon demersum), in fathead minnows (Pime-phales promelas) and in sediment were attained after 1, 2, and 6 months, respectively. After 1 year, most of the remaining TCDD was found in the pondweed, and after 2 years, through death of the plants, almost all the TCDD was found in the sediment phase that included plant detritus. Unidentified metabolites were confined to the aqueous phase and the plants (Tsushimoto et al. 1982). 

TCDD accumulation by plants has a minimal impact on the soil concentration of TCDD. 

A total of 739 g of plant matter was collected from Plot A on July 9, 1985. This is a replicate workup and analysis for the TCDD concentration. 

Control side of Plot C. The TCDD concentrations in the nursery dirt (1 to 4 ppb) were approximately 30 times lower than the concentrations in the control side of Plot C. Thus, the TCDD was apparently drawn up through the plant roots and stored in the plant cells. 

A TCDD material balance was done to determine the impact of the plant uptake of TCDD on the loss from the soil. It was assumed that all of the TCDD found in the plants came from a single 1 cm soil increment of density 1.5 g/cm3. Table III presents the results of this material balance calculation. The TCDD accumulation by the plants would change the soil concentration by less than 0.1 ppb over the time period of the field study. This is small change is well within the analytical and sampling error of this study and can be ignored as a significant TCDD loss mechanism. However, the possible movement of TCDD through the plants and the subsequent evaporation of the TCDD from the plant leaves can not be ruled out as a TCDD loss mechanism by this study. 

TCDD accumulation by the plants has a minimal impact on the soil concentration of TCDD. However, the possible movement of TCDD through the plants and the subsequent evaporation of the TCDD from the plant leaves can not be ruled out as a TCDD loss mechanism by this study. 

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