Concentration, 2,3,7,8-TCDD

Wl Water Hazardous air contaminants without acceptable ambient concentrations (2,3,7,8-TCDD). 0001 pounds/year... 

The value given in Table II for adrenals 21 days following administration suggests that this tissue may concentrate TCDD- C and/or a metabolite. This observation results probably from experimental error. The disintegrations per minute (dpm) above background for this tissue were only 17, 29, and 90. Since the total amount of tissue available for analysis was less than 20 mg, the multiplication factor may have magnified the error many fold. 

As shown by several investigations [91], the bromine-rich polybromide phase by itself is hardly flammable and fireextinguishing properties have been reported occasionally. The formation of polybrominated dibenzo-dioxins (PBrDD) and furans (PBrDF) due to the plastic-containing housing of a zinc-flow battery cannot be totally neglected in the case of a fire, but their concentrations are far away from the tetrachloro dibenzodioxine (TCDD) toxic equivalents even in a worst-case scenario. 

Because of its high toxicity, there is concern about very low levels of 2,3,7,8-TCDD in biota. This raises analytical problems, and high resolution capillary gas chromatography (GC) is needed to obtain reliable isomer-specific analyses at low concentrations. In the analysis of herring gull eggs collected from the Great Lakes, Hebert et al. (1994)... 

Toxic equivalency factors (TEFs) are estimated relative to 2,3,7,8-TCDD, which is assigned a value of 1. They are measures of the toxicity of individual compounds relative to that of 2,3,7,8-TCDD. A variety of toxic indices, measured in vivo or in vitro, have been used to estimate TEFs, including reproductive effects (e.g., embryo toxicity in birds), immunotoxicity, and effects on organ weights. The degree of induction of P450 lAl is another measure from which estimations of TEF values have been made. The usual approach is to compare a dose-response curve for a test compound with that of the reference compound, 2,3,7,8-TCDD, and thereby establish the concentrations (or doses) that are required to elicit a standard response. The ratio of concentration of 2,3,7,8-TCDD to concentration of test chemical when both compounds produce the same degree of response is the TEF. Once determined, a TEF can be used to convert a concentration of a dioxin-like chemical found in an environmental sample to a toxic equivalent (TEQ). 

Thus, [C] X TEE = TEQ i , i , where [C] = environmental concentration of planar polychlorinated compound. The TEQ is an estimate of the concentration of TCDD that would produce the same effect as the given concentration of the dioxin-like chemical. 

Whyte, J.J., Van den Heuvel, M.R.M., and Clemons, J.H.M. et al. (1998). Mammalian and teleost cell line bioassays and chemically derived 2,3,7,8-TCDD equivalent concentrations in lake trout from Lake Superior and Lake Ontario, North America. Environmental Toxicology and Chemistry 17, 2214-2226. 

PCP presents a different picture from that of the lower chlorophenols and their derivatives. The corresponding dioxin shows much more stability to light than does TCDD, enough to permit its prolonged existence at low concentrations in a photoreactor. As a phenol it can directly yield dioxins, a process favored by its normal mode of application as the sodium salt. Although octachlorodibenzo-p-dioxin has much lower mammalian toxicity than TCDD (6), its formation, properties, and effects demand additional investigation. Technical preparations of PCP are frequently mixtures of tetra- and pentachlorophenols consequently, hepta-and possibly hexachlorodibenzo-p-dioxins might be expected as photolysis products in addition to the octachloro derivative. 

Acnegenic Response. Both 2,3,7,8-TCDD and HCDD produced chloracne in the rabbit ear bioassay as indicated by the formation of comedones. Solutions of 2,3,7,8-TCDD (sample c) in benzene ranging in concentration from 0.04 /xg/ml to 400 ju,g/ml produced a positive response with severity increasing with concentration. A negative response was obtained with a solution of 0.004 ju,g/ml. In contrast, a chloroform solution of 1,2,3,4-TCDD, 50 jug/ml, did not produce a positive response. With HCDD (samples a, b, c, and d), a response was produced by solutions of 10 to 50 ju,g/ml in chloroform and dimethoxyethane. Chloroform extracts from 10% suspensions of 2,7-DCDD or OCDD were negative, indicating that these have a low order or possibly no acnegenic activity. 

Some alternative method had to be devised to quantify the TCDD measurements. The problem was solved with the observation, illustrated in Figure 9, that the response to TCDD is linear over a wide concentration range as long as the size and nature of the sample matrix remain the same. Thus, it is possible to divide a sample into two equal portions, run one, then add an appropriate known amount of TCDD to the other, run it, and by simply noting the increase in area caused by the added TCDD to calculate the amount of TCDD present in the first portion. Figure 9 illustrates the reproducibility of the system. Each point was obtained from four or five independent analyses with an error (root mean square) of 5-10%, as indicated by the error flags, which is acceptable for the present purposes. 

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... 

The objectives of the soil persistence experiments were (1) to learn the effect of soil type and concentration on the TCDD degradation rate, (2) to isolate and characterize degradation products from DCDD and TCDD, and (3) to determine whether chlorodioxins could be formed from chlorophenol condensation in the soil environment. This last study was essential since quality control at the manufacturing level could reduce or eliminate the formed dioxin impurity. But the biosynthesis of chlorodioxins by chlorophenol condensation in the soil environment could not be controlled and would have connotations for all chlorophenol-de-rived pesticides if formation did occur. The same question needed to be answered for photochemical condensation reactions leading to chloro-... 

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-... 

Tetrachlorodibenzo-p-dioxin (TCDD) is a contaminant in 2,4,5- trichlorophenoxyacetic acid (2,4,5-T) which may occur in the manufacturing process. Before 1971 some samples of 2,4,5-T contained from 2-50 ppm TCDD (i) in the technical acid. Highest concentrations of TCDD occurred before 1968. 

Treatment of the extract with UV light (4) for 16 hours completely destroyed TCDD in the amended soil. The extract from the unamended soil was not changed by irradiation. Peaks close to the TCDD peak in retention time ( 0.2 min) were not altered. Recovery of ca. 100% was obtained when 5 ppb TCDD was added to the soil. A peak should be discernible at a concentration of 1 ppb as seen on the control core. However, background interference, even in the cleaned up residue, increased tremendously at the very low levels, and confirmation of a peak s identity was very difficult. 

Although there is no way of knowing with certainty the concentration of TCDD in the off-loaded still bottoms, the waste holding tank in Verona from which the trucks were filled was sampled in August 1974 and was found to contain an average of 328 ppm TCDD. 

In total, 550 analyses were conducted from samples taken at this site. These data indicate that only 5.8 percent of the 10.9 acres contaminated represented the road surfaces originally sprayed. The remaining surface contamination probably resulted from dispersion by wind, vehicular traffic, runoff, etc. The total TCDD sprayed was probably about 340 grams, with 74 percent still on the areas sprayed. Mean, volume weighted, TCDD concentrations in the sprayed and dispersed areas were 469 and 31 ppb, respectively. Concentrations in individual composite samples collected from sprayed areas ranged up to 1,800 ppb. About 90 percent of the TCDD was contained in 13 percent of the soil volume. 

Areal Variation. One objective of the sampling comparison studies was to determine the variation in TCDD concentration over a small area to estimate the error associated with a grab sample concentration. Accordingly, a one-square-yard area was selected adjacent to a previously sprayed road. The center of the test area was about 6 feet from a sprayed road shoulder. This one-square-yard area was divided into nine one-square-foot areas. Using clean spoons and knives, a single scoop was collected from the center of each one-square-foot area down to a depth of 2 inches. The data are presented in Figure 1. 

The data presented In Figures 2, 3, and 4 are from five different laboratories However, the samples from any one method In each segment were sent to the same contractor thus. Interlaboratory analytical variation Is not a factor In the data columns, but It may be a factor In the data rows The estimated Interlaboratory and Intralaboratory relative standard deviations for TCDD concentrations of 2 to 12 ppb range from 9 to 18 percent and 5 to 13 percent, respectively ... 

Figure 2. Road centerline TCDD concentrations (ppb) at segment F-1.

The large areal variation in environmental TCDD concentrations is confirmed by the analytical data resulting from using the four different methods to obtain samples at depth. An examination of Figure 3 which presents road centerline data from two 15-foot segments shows variations in the upper six inches ranging, from 295 to 895 and from 2.1 to 1020. 

Figure 5. Minimum and maximum mean TCDD concentrations and relative standard deviations.

Concentrations of TCDD can be expected to vary widely within relatively small areas. 

When pushed to the limit by overriding human health concerns, residue chemists have achieved detection limits of Ippt (Ingkg ) or even into the low ppqr (1 pg kg ) range. An example at the 1 ppt level is provided by methods for 2,3,7,8-tetrachlorodibenzodioxin (TCDD) in milk and TCDD in adipose tissue. Eor relatively clean matrices such as water and air, preconcentration on solid-phase adsorbents followed by GC or gas chromatography/mass spectrometry (GC/MS) can provide detection limits of 1 ng m and less for air (examples in Majewski and Capel ) and 1 ngL and less for water (examples in Larson et A summary of units of weight and concentration used to express residue data is given in Table 1. 

Although the effects of chronic exposure of humans to low levels of POPs are difficult to predict, some biological effects have been described. For example, exposure of children to PCBs and PCDD/Fs may be linked to an elevated risk for infectious diseases. Exposure of pregnant women to PCDD/Fs may cause lower fertility in their male offspring. The adverse effects to human health of acute and chronic exposure of high concentrations of POPs, especially among industrial workers exposed to daily intakes of chemicals, are more evident. Elevated concentrations of DDE and TCDD have been associated with the development of cancers such as breast cancer, leukaemia and thyroid cancer. Dioxin exposure may also be associated with immunotoxicity, reproductive diseases and neurotoxicity. Extreme exposure to chlorinated compounds has resulted in death [101]. 

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