2,3,7,8-Tetrachlorodibenzofuran

SRP: The most favorable course of action is to use an alternative chemical product with less inherent propensity for occupational exposure or environmental contamination. Recycle any unused portion of the material for its approved use or return it to the manufacturer or supplier. Ultimate disposal of the chemical must consider: the material's impact on air quality; potential migration in soil or water; effects on animal, aquatic, and plant life; and conformance with environmental and public health regulations.

0.0013 [mg/m3]

0.014 [mg/m3]

0.085 [mg/m3]

2,3,7,8-Tetrachlorodibenzofuran levels of 17 and 60 pg/g were detected in the adipose tissue and liver, respectively, of a Yusho baby from Taiwan(1). A mean concn of 3 pg/g was found in adipose tissue of 31 Swedes(2). Concns of a trace to 0.3 ppb were detected in liver and adipose tissue of patients from Japan and Taiwan who consumed contaminant rice oils(3). The mean concn of 2,3,7,8-tetrachlorodibenzofuran in adipose tissue of 13 workers exposed to phenoxy herbicides was 3.7 pg/g, while the mean concn in 18 non-exposed subjects was 4.2 pg/g(4). The concn of 2,3,7,8-tetrachlorodibenzofuran usually found in human adipose tissue has been reported to be 3-30 pg/g(5). The USEPA's National Human Adipose Tissue Survey for fiscal year 1982 detected a mean conc of 9.1 pg/g with a range of <2.0 to 32 pg/g(6). The avg concn of 2,3,7,8-tetrachlorodibenzofuran in whole blood from the general U.S. population (N=100) was 3.1 parts per trillion on a lipid basis(8). Blood samples collected from humans who had been drinking cow's milk for a long time from dairy farms near a metal reclamation plant contained 2,3,7,8-tetrachlorodibenzofuran at 13.1 and 55.0 pg/g fat(7). Blood obtained from humans in Ho Chi Minh City (n=50), Dong Nai (n=33), Hanoi (n=32), Germany (n=85), and America (n=100) contained 2,3,7,8-tetrachlorodibenzofuran at 3.4, 12, <2.4, 3.6, and 5.2 parts per trillion, lipid based, respectively(2). 2,3,7,8-Tetrachlorodibenzofuran was measured in infant organs (n=3) at <1.0, 3.2, <1.0, <0.5, and <0.2 parts per trillion, fat wt, in spleen, thymus, liver, brain (gray matter), and brain (white matter), respectively(9). The mean concn of 2,3,7,8-tetrachlorodibenzofuran in 13 adipose tissue samples collected in individuals from Japan was 9 pg/g wet wt (range, 3-12 pg/g wet wt)(10). Blood samples of young Japanese women (age of approx 20 years old who have not had children) collected between June 1993 to June 1994 contained 2,3,7,8-tetrachlorodibenzofuran at a mean concn of 0.012 pg/g whole basis (or 4.3 pg/g lipid basis)(11). The mean concn of 2,3,7,8-tetrachlorodibenzofuran in German general population human blood was 3.78 pg/g lipid (n=228), 2.60 pg/g lipid (n=744), and 0.57 pg/g lipid (n=9) for the periods 1989, 1989-1998, and 1997/98, respectively(12). The mean concn of 2,3,7,8-tetrachlorodibenzofuran in the blood of Bavarian chimney sweep workers was 6.08 pg/g blood fat (n=227; range, 0.17-67.41 pg/g blood fat) while the mean concn in a control group was 3.05 pg/g blood fat (n=6; range, 0.67-18.81 pg/g blood fat)(13). The mean concn of 2,3,7,8-tetrachlorodibenzofuran in adipose tissues of non-occupationally exposed persons in France was 0.42 pg I-TEQ/g lipid (or 4.2 pg/g lipid based on I-TEF of 0.1) (14,15).

Levels of <1-5 ng/kg were detected in human milk samples from Europe in 1985(1). Concns of 2,3,7,8-tetrachlorodibenzofuran in human milk fat from Dutch women were 1.3 to 5.8 mg/kg (median=2.5; n=10)(2); concns in human milk from German women were from 1.1-8.2 parts per trillion in Berlin (mean 2.8 parts per trillion; n=35), 1.1-6.1 parts per trillion in Weiden (mean 3.3 parts per trillion; n=14), 1.7-12 parts per trillion in Rheinfelden (mean 5.8; n=9), 0.5-4.0 in Recklinghausen (mean 14.; n=10) and 0.9-2.3 parts per trillion fat wt basis in Flensburg (mean 1.6; n=6)(3). Human milk samples from Germany contained 2,3,7,8-tetrachlorodibenzofuran at a mean concn of 2.5 pg/g fat (range= 0.2 to 12; median=2.1; n=112)(4). 2,3,7,8-Tetrachlorodibenzofuran was detected in human milk samples mainly collected in North Rhine Westphalia, Germany from 1986 to 1991 at a mean concn of 1.7 pg/g fat (n=526; median=1.5; range=0.2 to 7.7 pg/g fat)(5). Human milk samples from Sweden and Germany contained 2,3,7,8-Tetrachlorodibenzofuran levels of a trace to 3.3 pg/g (means of 0.6-1.9 pg/g)(6). Human milk samples from Paris, France and Madrid, Spain contained 2,3,7,8-tetrachlorodibenzofuran levels of 1.8 and 1.02 pg/g fat wt, respectively (n=15 and 13, respectively)(7). Human milk samples from Japan contained 2,3,7,8-tetrachlorodibenzofuran levels of 0.051 pg/g whole (n=26; range=0.006 to 0.13 pg/g whole)(8). Human milk from women in the U.S., Germany, and Vietnam (collected in 1973) contained 2,3,7,8-tetrachlorodibenzofuran at 2.85 (n=42), 2.0 (n=185), and 0.5 (n=7) parts per trillion, respectively(9). Human milk samples from Sweden and Germany contained 2,3,7,8-tetrachlorodibenzofuran levels of a trace to 3.4 pg/g (means of 0.6-1.9 pg/g)(10). Levels of <1-5 ng/kg were detected in human milk samples from Europe in 1985(11).

The concns of 2,3,7,8-tetrachlorodibenzofuran in the breast milk of one mother's lactation over a period of 3 years were as follows: February 1992, 1.7 parts per trillion lipid basis; March 1993, 1.09 parts per trillion lipid basis; July 1994, 0.52 parts per trillion lipid basis; December 1994, 0.30 parts per trillion lipid basis; September 1995, 0.5 parts per trillion lipid basis(1). The concn of 2,3,7,8-tetrachlorodibenzofuran in one mother's breast milk 1 and 5 months after postpartum was 0.98 parts per trillion lipid basis after 1 month and 0.42 parts per trillion lipid basis after 5 months(1). The concn of 2,3,7,8-tetrachlorodibenzofuran in a pooled sample of human milk (n=40 mothers) from Rio de Janeiro, Brazil in 1992 was 0.3 pg/g milk fat(2).

CDFs cause vomiting and diarrhea, anemia, more frequent lung infections, numbness and other effects on the nervous system, and mild changes in the liver. However, there were no permanent liver changes or definite liver damage found in people who ingested CDFs. (L952)

ED50 Cyprinus carpio (Carp) increased enzyme activity in the liver, single ip dose 17.75 mmol/kg 2 weeks post-exposure /Conditions of bioassay not specified/

LD50 Oncorhynchus mykiss (Rainbow trout, newly fertilized eggs) injection 1.5 ng/g /Conditions of bioassay not specified/

LC50 Oryzias latipes (Japanese medaka, embryos) 16 ng/L 3 days post-hatch (95% CI: 12-22 ng/L), static

EC50 Oryzias latipes (Japanese medaka, embryos) abnormal growth (visible lesions) 0.007 ug/L >13 days exposure (95% CI: 0.005-0.012 ng/L), static

EC50 Oryzias latipes (Japanese medaka, embryos) decreased hatch 29.5 ng/L/72 hr /Conditions of bioassay not specified/

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 85,000(SRC), determined from a log Kow of 6.53(2) and a regression-derived equation(3), indicates that 2,3,7,8-tetrachlorodibenzofuran is expected to be immobile in soil(SRC). While biodegradation under aerobic conditions is not expected to be a major fate process for this compound in soil, based on structurally-similar compounds(SRC), both volatilization and photolysis may occur resulting in the transport or degradation of 2,3,7,8-tetrachlorodibenzofuran from soil surfaces(SRC). Volatilization of 2,3,7,8-tetrachlorodibenzofuran from moist soil surfaces is expected to be an important fate process for this compound(SRC) given an estimated Henry's Law constant of 1.5X10-5 atm-cu m/mole(SRC), using a fragment constant estimation method(4), although adsorption is expected to attenuate this process. 2,3,7,8-Tetrachlorodibenzofuran is not expected to volatilize from dry soil surfaces(SRC) based upon an estimated vapor pressure of 1.5X10-6 mm Hg(SRC), determined from a fragment constant method(5). The potential for direct photolysis on soil surfaces may exist as 2,3,7,8-tetrachlorodibenzofuran has been shown to absorb light at 309 and 316 nm in tetrachloromethane(6).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 85,000(SRC), determined from a log Kow of 6.53(2), indicates that 2,3,7,8-tetrachlorodibenzofuran is expected to adsorb to suspended solids and sediment in water(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 1.5X10-5 atm-cu m/mole(SRC), developed using a fragment constant estimation method(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 4 and 37 days, respectively(SRC). However, volatilization from water surfaces is expected to be attenuated by adsorption to suspended solids and sediment in the water column(SRC). The estimated volatilization half-life from a model pond is 5,800 years if adsorption is considered(5). According to a classification scheme(6), BCF values of 2,042; 2,630; and 4,467(7) in fish suggest that the potential for bioconcentration in aquatic organisms is very high(SRC). This compound is expected to be resistant to aerobic biodegradation based on data for structurally-similar compounds containing several chlorine atoms, but may be susceptible to reductive dechlorination under anaerobic conditions as may be found in sediment(SRC). A minimum half-life of 60.5 years, however, was determined in anaerobic sediment collected from the Baltic sea(8). Photolysis, both direct and indirect, may result in the degradation of 2,3,7,8-tetrachlorodibenzofuran in water(SRC). Half-lives of 11 hours in sunlight for 2,3,7,8-tetrachlorodibenzofuran in distilled water versus 5.9 to 6.3 hours in natural waters were measured(9); another experiment reported a half-life of 1.2 days in natural water exposed to sunlight(10).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), 2,3,7,8-tetrachlorodibenzofuran, which has an estimated vapor pressure of 1.5X10-6 mm Hg at 25 °C(SRC), using a fragment constant estimation method(2), will exist in both the vapor and particulate phase in the ambient atmosphere(SRC). Monitoring of stack effluents from municipal waste incinerators has also shown that 2,3,7,8-tetrachlorodibenzofuran can occur at significant levels in the atmosphere in both the vapor and particulate phase(3). Vapor-phase 2,3,7,8-tetrachlorodibenzofuran is degraded in the atmosphere by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life for this reaction in air is estimated to be 63 days(SRC), calculated from its rate constant of 2.5X10-13 cu cm/molecule-sec at 25 deg(SRC), determined using a structure estimation method(4). No data are available to estimate rates at which particulate-phase 2,3,7,8-tetrachlorodibenzofuran may chemically degrade in air although the potential for direct photolysis exists as this compound has been shown to absorb light at 309 and 316 nm(5). Particulate-phase 2,3,7,8-tetrachlorodibenzofuran may be removed from the air by wet and dry deposition(SRC).

The migration of 2,3,7,8-tetrachlorodibenzofuran present in bleached paper products to food within the container was measured for a variety of articles; 18.3% migration in 12 days (at 4 °C) for polyethylene (PE) coated carton to milk, 16.1% migration in 12 days for PE-coated carton to cream, 0.1% migration for ethylene vinyl alcohol polymer coated carton to juice, 35% migration in 12 minutes (85 °C) for coffee filter to coffee, 0.39% migration in 30 minutes (90 °C) for PE-coated cup to coffee, 18% migration in 30 minutes (60 °C) for clay-coated plates to beef hash, and 2.2% migration in 4 minutes (200 °C) for microwave popcorn bag to popcorn(1). Concns of 2,3,7,8-tetrachlorodibenzofuran in oysters, blue crab (body) and blue crab (claw) seafood samples collected in southern Mississippi in April and May 1994 from local grocery stores were 14 to 48, 26 to 51, and 9.8 to 16 pg/g fat, respectively(1). Concns of 2,3,7,8- tetrachlorodibenzofuran in crawfish (head), crawfish (tail), catfish (farm-raised), mullet (fillet) and in Spanish mackerel seafood samples collected in southern Mississippi were 5.1 to 5.4, 2.8 to 9.5, 0.64 to 0.99, 1.1 to 7.8 and 11 pg/g fat, respectively(2). Concns of 2,3,7,8-tetrachlorodibenzofuran in chicken (meat), chicken (liver), ground beef and sausage samples collected in southern Mississippi were 0.74 to 0.83, 0.4 to 0.99, 0.056 to 0.077 and 0.11 to 0.25 pg/g fat, respectively(2). Concns of 2,3,7,8-tetrachlorodibenzofuran in whole milk, cheddar cheese, butter and eggs collected in southern Mississippi were 0.088 to 0.14, 0.039 to 0.075, 0.037 to 0.071, and 0.08 to 0.11 pg/g fat, respectively(2). 107 food samples collected in Germany were analyzed for 2,3,7,8-tetrachlorodibenzofuran concns; concns in cow's milk (n=10; range=<0.5-10; mean=4.1), cheese (n=10; range=<0.5-2.6; mean=1.1), butter (n=5; mean=<0.3), beef (n=3; mean=<0.3), veal (n=4; range=<0.3-0.5; mean=0.2), pork (n=3; mean=<0.3), sheep (n=2; mean=<0.3), chicken (n=2; range=1.2-4.0; mean=2.6), canned meat (n=2; mean=<0.3), and lard (n=4; range=<0.3-1.0; mean=0.5) were measured(3). Concns of 2,3,7,8-tetrachlorodibenzofuran in 14 samples of canned corn beef hash ranged from not detected to 12 pg/kg, whole wt basis(4).

Between 1993 and 1996; 1,414 food samples collected in southwestern Germany were monitored for 2,3,7,8-tetrachlorodibenzofuran; concns in milk (n=538; mean=0.08; range=0.00-0.62 pg/g fat), butter (n=222; mean=0.04; range=0.00-0.66 pg/g fat), eggs (n=218; mean=1.54; range=0.00-31.76 pg/g fat), meat (n=107; mean=0.30; range=0.04-3.01 pg/g fat), and fish (n=138; mean=66.46; range=0.00-4,280.75 pg/g fat) were measured(1). Concns of 2,3,7,8-tetrachlorodibenzofuran in a fast food hamburger, pizza, fried chicken, and ice cream were undetected, undetected, 0.07 parts per trillion wet wt, and undetected, respectively (detection limit in pg/g)(2). 2,3,7,8-Tetrachlorodibenzofuran was reported in the hepatopancreas of blue crab (602.4-674.1 pg/g wet wt), blue crab meat (11.0-15.5 pg/g wet wt), lobster hepatopancreas (347.8-383.5 pg/g wet wt), lobster meat (3.5-4.1 pg/g wet wt) and in striped bass meat (51.9-85.5 pg/g wet wt) collected from Newark Bay and the New York Bight(3). Uncooked and cooked hamburger contained 2,3,7,8-tetrachlorodibenzofuran at mean concns of 32.3 (range 28.7 to 35.4 pg/kg) and 41.0 pg/kg (range 30.5 to 53.9 pg/kg), respectively(4). Uncooked and cooked bacon contained 2,3,7,8-tetrachlorodibenzofuran at mean concns of 79.8 (range 67.4 to 92.3 pg/kg) and 138.0 pg/kg (range 113.8 to 158.0 pg/kg), respectively(4). Uncooked and cooked catfish fillets with skin contained 2,3,7,8-tetrachlorodibenzofuran at mean concns of 87.1 (range 54.5 to 111.4 pg/kg) and 51.9 pg/kg (range 35.0 to 62.6 pg/kg), respectively(4). Infant formula was analyzed for the presence of 2,3,7,8-tetrachlorodibenzofuran; Similac (cow's milk), Isomil (cow's milk), and Prosobee (soy-based) infant formula obtained in 1986/1987 contained undetectable quantities of this compound (<0.5 to 1.0 parts per trillion lipid basis)(5). Retail fish purchased in Norwich, England contained 2,3,7,8-tetrachlorodibenzofuran: plaice (0.90 to 1.86 ng/kg wet wt), mackeral (2.61 ng/kg wet wt), herring (2.47 ng/kg wet wt), cod (0.22 ng/kg wet wt), skate (0.31 ng/kg wet wt), coley (0.14 ng/kg wet wt)(6). The concn of 2,3,7,8-tetrachlorodibenzofuran in butter samples from Australia ranged from <0.02 to 0.09 pg/g fat(7). The concn of 2,3,7,8-tetrachlorodibenzofuran in farm-raised catfish from southeastern United States ranged as follows: catfish nuggets, 1.1-1.2 pg/g lipid; catfish fillets (brand A), 1.1-1.2 pg/g lipid; catfish fillets (brand B), 0.68 pg/g lipid; Mississippi commercial fillets, 0.24-0.71 pg/g lipid; Arkansas commercial fillets, 0.45-0.70 pg/g lipid(8).

Six samples of cow's milk from Switzerland had concns of 0.021-0.035 ng/kg, with the higher levels found in samples collected in the vicinity of incinerators(1). 2,3,7,8-Tetrachlorodibenzofuran was present in cow's milk samples from 5 Connecticut dairy farms at concns from 5.0 to 14 fg/g (n = 17; 6 samples below detection; avg concn = 8.7 fg/g in 1991). Following the placement and start-up of a municipal waste incinerator nearby, concns of 2,3,7,8-tetrachlorodibenzofuran in milk collected at the same farms ranged from 5.0 to 23 fg/g (n = 12; 1 sample below detection; avg concn = 13 fg/g in 1993)(2). 8 samples of cow's milk collected in Germany contained 2,3,7,8-tetrachlorodibenzofuran at concns of <0.1 to 1.4 parts per trillion, fat wt basis(3). Cow's milk samples from a rural area, an industrialized area, an area close to a metal reclamation plant and milk from a paper container were analyzed for 2,3,7,8-tetrachlorodibenzofuran; mean concns of 0.7, 1.2, 2.5 and 9.6 pg/g, fat wt basis, respectively, were measured(4). Cow's milk packaged in paper and plastic was collected from retail stores in the San Francisco Bay Area in 1989/1990; cow's milk in paper containers contained 2,3,7,8-tetrachlorodibenzofuran at 6.5 to 40 pg/g fat, 3.2 to 3.7, and <0.4 pg/g fat for three separate paper container sources and was <0.6 pg/g fat for milk in a plastic container(5). 160 samples of cows milk collected from single farms in Bavaria contained 2,3,7,8-tetrachlorodibenzofuran (range = 0.1 to 1.46 pg/g, fat basis)(6). Migration of 2,3,7,8-tetrachlorodibenzofuran from bleached paperboard cartons into milk was studied; 6.8, 10.2, 20.1 and 35.1 pg/g, milk fat basis, was reported after 24, 48, 120, and 288 hours, respectively(7). Milk products purchased between 1985 and 1988 in retail stores in 5 major cities across Canada, packaged in plastic-coated bleached paperboard cartons, contained 2,3,7,8-tetrachlorodibenzofuran; whole milk had a mean concn of 1.0 pg/g (range 0.039 to 2.5 pg/g; plastic containers from <0.02 to 0.18 pg/g; glass containers from <0.02 to 0.61 pg/g), 2% milk had a mean concn of 1.0 pg/g (range 0.030 to 2.8 pg/g; undetected (<0.02 pg/g) in plastic and glass containers) and skim milk had a mean concn of 0.57 pg/g (range 0.13 to 1.4 pg/g; undetected in plastic containers)(8).

Levels of <1-5 ng/kg were detected in human milk samples from Europe in 1985(1). Concns of 2,3,7,8-tetrachlorodibenzofuran in human milk fat from Dutch women were 1.3 to 5.8 mg/kg (median=2.5; n=10)(2); concns in human milk from German women were from 1.1-8.2 parts per trillion in Berlin (mean 2.8 parts per trillion; n=35), 1.1-6.1 parts per trillion in Weiden (mean 3.3 parts per trillion; n=14), 1.7-12 parts per trillion in Rheinfelden (mean 5.8; n=9), 0.5-4.0 in Recklinghausen (mean 14.; n=10) and 0.9-2.3 parts per trillion fat wt basis in Flensburg (mean 1.6; n=6)(3). Human milk samples from Germany contained 2,3,7,8-tetrachlorodibenzofuran at a mean concn of 2.5 pg/g fat (range= 0.2 to 12; median=2.1; n=112)(4). 2,3,7,8-Tetrachlorodibenzofuran was detected in human milk samples mainly collected in North Rhine Westphalia, Germany from 1986 to 1991 at a mean concn of 1.7 pg/g fat (n=526; median=1.5; range=0.2 to 7.7 pg/g fat)(5). Human milk samples from Sweden and Germany contained 2,3,7,8-tetrachlorodibenzofuran levels of a trace to 3.3 pg/g (means of 0.6-1.9 pg/g)(6). Human milk samples from Paris, France and Madrid, Spain contained 2,3,7,8-tetrachlorodibenzofuran levels of 1.8 and 1.02 pg/g fat wt, respectively (n=15 and 13, respectively)(7). Human milk samples from Japan contained 2,3,7,8-tetrachlorodibenzofuran levels of 0.051 pg/g whole (n=26; range=0.006 to 0.13 pg/g whole)(8). Human milk from women in the U.S., Germany, and Vietnam (collected in 1973) contained 2,3,7,8-tetrachlorodibenzofuran at 2.85 (n=42), 2.0 (n=185), and 0.5 (n=7) parts per trillion, respectively(9). Human milk samples from Sweden and Germany contained 2,3,7,8-tetrachlorodibenzofuran levels of a trace to 3.4 pg/g (means of 0.6-1.9 pg/g)(10). Levels of <1-5 ng/kg were detected in human milk samples from Europe in 1985(11).

Halogenated dibenzofurans (PCDFs and PBDFs) bind the aryl hydrocarbon receptor (AhR), which increases its ability to activate transcription in the XRE (xenobiotic resoponse element) promoter region. Specifically AhR binds to the PCDF, translocates it to the nucleus and together with hydrocarbon nuclear translocator (ARNT) and xenobiotic responsive element (XRE) increases the expression of CYP1A1 and aryl hydrocarbon hydroxylase (CYP1B1). AhR signaling also increseases conversion of arachidonic acid to prostanoids via cyclooxygenase-2, alters Wnt/beta-catenin signaling downregulating Sox9 and alters signaling by receptors for inflammatory cytokines. AhR signalling also alters proteasomal degradation of steroid hormone receptors, alters cellular UVB stress response and changes the differentiation of certain T-cell subsets. The resulting AhR mediated activation and alteration leads to body weight loss, cancer and thymic atrophy (characteristic of immune and endocrine disruption) which are common toxic responses to PCDFs and related toxic halogenated aryl hydrocarbons.

/BIRDS and MAMMALS/ The insectivorous tree swallow was chosen species to investigate the uptake of pulp mill-related chlorinated hydrocarbons from emergent aquatic insects /at locations/. ... on two river systems in British Columbia, Canada. Also, 16-day-old nestlings were collected and analysed for polychlorinated biphenyls (PCBs), polychlorinated dibenzo-p-dioxins (PCDDs) and dibenzofurans (PCDFs), pesticides, chlorophenols and chloroguaiacols. Most reproductive parameters were not different between populations at upstream and downstream locations, and were equivalent to or greater than those recorded for other tree swallow populations. Chlorinated hydrocarbon contamination of nestlings was low at all sites. The highest tissue concentrations were detected downstream of pulp mills on the Fraser River, where PCDD and PCDF patterns along with the presence of pentachlorophenol (PCP) suggested that the primary source of contaminants was past use of PCP for timber preservation. Although the absolute tissue concentration of contaminants was less, the toxic concentration (as estimated with I-TEQs) was greatest in nestlings downstream of a pulp mill on the Thompson River. The proportionately larger contributions from 2,3,7,8-TCDF and PCB-77 elevated these TEQs in comparison to other populations. Nest success was the one reproductive measure that showed substantial reductions in downstream populations on both rivers.

/BIRDS and MAMMALS/ Captive harbour seals fed a diet of Baltic Sea herring, which was highly contaminated with PCBs, PCDDs and PCDFs, did not bioaccumulate the PCDDs and PCDFs. During a 15 day fasting experiment at the end of this study, blood 2,3,7,8-TCDD adn 2,3,7,8-TCDF concentrations actually declined, presumably reflecting metabolism and excretion of these contaminants.

/AQUATIC SPECIES/ Median mortality of 120 days observed in juvenile Atlantic salmon (Salmo salar) fed on dry fish food containing tetrachlorodibenzofuran at 2.8 ug/g. Tetrachlorodibenzofuran was not detected at 0.02 ug/g detection limit in any fish.

Listed as a hazardous air pollutant (HAP) generally known or suspected to cause serious health problems. The Clean Air Act, as amended in 1990, directs EPA to set standards requiring major sources to sharply reduce routine emissions of toxic pollutants. EPA is required to establish and phase in specific performance based standards for all air emission sources that emit one or more of the listed pollutants. 2,3,7,8-Tetrachlorodibenzofuran is included on this list.

Formed as unwanted by-product during the manufacturing of chlorinated compounds; Not commercially used or produced; [HSDB]

There is no industrial use for PCDFs.

CDFs are created from production of coal tar and during incineration. They are used as insecticides, in the production of PVC, and in industrial bleaching. (L952)

(1977) NOT PRODUCED COMMERCIALLY IN USA

(1979) NOT PRODUCED COMMERCIALLY IN USA

PCDFs are formed as unwanted by-products during the manufacturing of chlorinated compounds such as trichlorophenol, 2,4,5-trichlorophenoxyacetic acid, pentachlorophenol, and PCBs.

Except for the production of reference standards, .../polychlorinated dibenzofurans/ PCDFs are not intentionally manufactured. In manufacturing processes their formatio theoretically occurs when free chlorine is present in one or several of the following reaction conditions: alkaline medium, temperature >150 °C, UV light, and radical-forming substances. In the past, metallurgic procedures (e.g., the production of copper by heating of ores with NaCl up to 500 °C) resulted in high amounts of ...PCDFs as byproducts. In the production of /chlorinated benzenes, chlorinated phenols, polychlorinated biphenyls/ and various chlorinated pesticides, ...PCDFs are formed as undesirable byproducts. They arise preferably by intermolecular condensation of ortho-chlorophenols or ortho-chlorophenoxy derivatives during the production of /pentachlorophenol/. In addition, intramolecular cyclization reactions of ...predibenzofurans may also result in the formation of ...PCDFs. /Polychlorinated dibenzofurans/

Thermal waste treatment processes are another important source of ...PCDF production. Two major pathways of ...PCDF formation include the combustion and pyrolysis of organochlorine compounds, and the combustion and pyrolysis of non-chlorinated organic material in the presence of chlorides, both of which lead to a 'de novo' synthesis. The recycling of metal cables may also result in ...PCDF formation (e.g., chlorine is formed by burning of the insulating polyvinylchloride which causes a 'de novo' synthesis of ...PCDFs). /Polychlorinated dibenzofurans/

When specific /polychlorinated biphenyls/ were pyrolyzed in quartz ampules between 500 and 700 °C, /polychlorinated dibenzofuran (PCDF)/ yields in the 1-10% range could be obtained, though they were accompanied by many other products, including chlorinated benzenes, naphthalenes, and hydroxy PCBs. ...There appear to be four major paths for production of PCDFs form PCBs: loss of two ortho chlorines, loss of ortho hydrogen as well as chlorine, loss of an ortho hydrogen as well as chlorine but involving a shift of chlorine from the 2 to the 3 position, and loss of two ortho hydrogens. /Polychlorinated dibenzofurans/