ジベンゾ[b,e][1,4]ジオキシン

TERRESTRIAL FATE: Based on a classification scheme(1), an estimated Koc value of 5,200(SRC), determined from a log Kow of 4.3(2) and a regression-derived equation(3), indicates that dibenzo-p-dioxin is expected to be immobile in soil(SRC). Volatilization of dibenzo-p-dioxin from moist soil surfaces is expected to be an important fate process(SRC) given an estimated Henry's Law constant of 1.1X10-4 atm-cu m/mole(SRC), derived from its vapor pressure, 4.12X10-4 mm Hg(2), and water solubility, 0.901 mg/l(4). However, adsorption to soil is expected to attenuate volatilization(SRC). Dibenzo-p-dioxin is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(2). Although pure culture studies have shown that dibenzo-p-dioxin can be metabolized(5-8), insufficient data are available to predict the importance of biodegradation in soil(SRC).

AQUATIC FATE: Based on a classification scheme(1), an estimated Koc value of 5,200(SRC), determined from a log Kow of 4.3(2) and a regression-derived equation(3), indicates that dibenzo-p-dioxin is expected to adsorb to suspended solids and sediment(SRC). Volatilization from water surfaces is expected(3) based upon an estimated Henry's Law constant of 1.1X10-4 atm-cu m/mole(SRC), derived from its vapor pressure, 4.12X10-4 mm Hg(2), and water solubility, 0.901 mg/l(4). Using this Henry's Law constant and an estimation method(3), volatilization half-lives for a model river and model lake are 9 hrs and 9 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 293 days if adsorption is considered(5). According to a classification scheme(6), an estimated BCF of 410(SRC), from its log Kow(2) and a regression-derived equation(7), suggests the potential for bioconcentration in aquatic organisms is high(SRC). Exposure of pure aqueous solutions of dibenzo-p-dioxin in pyrex tubes to outdoor October sunlight resulted in decompositions of up to 6% in three days of exposure(8); however, addition of small amounts of nitrate ion to the aqueous solutions resulted in disappearances of 70% in one day and 92% in three days(8). Although pure culture studies have shown that dibenzo-p-dioxin can be metabolized(9-12), insufficient data are available to predict the importance of biodegradation in water(SRC).

ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile organic compounds in the atmosphere(1), dibenzo-p-dioxin, which has a vapor pressure of 4.12X10-4 mm Hg at 25 °C(2), is expected to exist solely as a vapor in the ambient atmosphere(SRC). However, it has been shown that dibenzo-p-dioxin can become irreversibly adsorbed to incinerator stack emissions of fly ash under certain operating conditions(3); therefore, particulate phase dibenzo-p-dioxin may also occur in the ambient environment(SRC). Vapor-phase dibenzo-p-dioxin 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 1.3 days(SRC), calculated from its rate constant of 12X10-12 cu cm/molecule-sec at 25 °C(4). Particulate-phase dibenzo-p-dioxin may be removed from the air by wet and dry deposition(SRC). Dibenzo-p-dioxin has a strong absorption maximum at 290 nm in methanol(5) and has the potential for direct photolysis in the atmosphere(SRC).

The following link will take the user to the National Toxicology Program (NTP) Test Agent Search Results page, which tabulates all of the "Standard Toxicology & Carcinogenesis Studies", "Developmental Studies", and "Genetic Toxicity Studies" performed with this chemical. Clicking on the "Testing Status" link will take the user to the status (i.e., in review, in progress, in preparation, on test, completed, etc.) and results of all the studies that the NTP has done on this chemical. [http://ntp-apps.niehs.nih.gov/ntp_tox/index.cfm?fuseaction=ntpsearch.searchresults&searchterm=262-12-4]

The Koc of dibenzo-p-dioxin is estimated as 5,200(SRC), using a log Kow of 4.3(1) and a regression-derived equation(2). According to a classification scheme(3), this estimated Koc value suggests that dibenzo-p-dioxin is expected be immobile in soil(SRC).

AEROBIC: Pure culture biodegradation studies have shown that dibenzo-p-dioxin is metabolized by Pseudomonas, Beijerinckia, and Sphingomonas species (1-4). Dibenzo-p-dioxin is transformed to the 2-hydroxy-derivative and catechol(3). The specific oxygen uptake rate for dibenzo-p-dioxin by resting cells of Sphingomonas sp. strain SS3 after growth with polyhalogenated diphenyl ethers, 4-fluorodiphenyl ether, 4-chlorodiphenyl ether, and acetate were 29,27,25,and <5 nmoles of O2 consumed per minute per mg protein, respectively(5).

Dibenzo-para-dioxin

Group 3: Not classifiable as to its carcinogenicity to humans

Volume 69: (1997) Polychlorinated Dibenzo-para-dioxins and Polychlorinated Dibenzofurans

1997

1997

Dibenzo-p-dioxin

An estimated BCF of 410 was calculated for dibenzo-p-dioxin(SRC), using a log Kow of 4.3(1) and a regression-derived equation(2). According to a classification scheme(3), this BCF suggests the potential for bioconcentration in aquatic organisms is high(SRC).

The Henry's Law constant for dibenzo-p-dioxin is estimated as 1.1X10-4 atm-cu m/mole(SRC) derived from its vapor pressure, 4.12X10-4 mm Hg(1), and water solubility, 0.901 mg/l(2). This Henry's Law constant indicates that dibenzo-p-dioxin is expected to volatilize from water surfaces(3). Based on this Henry's Law constant, the volatilization half-life from a model river (1 m deep, flowing 1 m/sec, wind velocity of 3 m/sec)(3) is estimated as 9 hours(SRC). The volatilization half-life from a model lake (1 m deep, flowing 0.05 m/sec, wind velocity of 0.5 m/sec)(3) is estimated as 9 days(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 293 days if adsorption is considered(4). Dibenzo-p-dioxin is not expected to volatilize from dry soil surfaces(SRC) based upon its vapor pressure(1).

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ Groups of 35 male and 35 female Osborne-Mendel rats, five weeks of age, were administered 0 (control), 5000 (low-dose) or 10,000 (high-dose) mg/kg of diet (ppm) dibenzo-para-dioxin (purity 99.5%) in the diet for 110 weeks. Mean body weights of the treated male and female rats were lower that those of the corresponding controls. In the male rats, survival in the control group was lower than in the treated groups (p = 0.011, Tarone test). Survival of high-dose female rats was lower than that of the control and low-dose groups (p = 0.007, Tarone test). At week 90 of the study, 24/35 control and 29/35 rats in each treated group of males were still alive, and 32/35, 31/35 and 20/35 control, low-dose and high-dose female rats, respectively, were still alive. Tumors were not induced in rats of either sex at significantly higher incidence in the treated groups than in the corresponding control groups.

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ ...Groups of 30 male and 30 female Swiss-Webster mice received thrice weekly skin applications of 0.2 ml acetone containing... 80 mg/kg... unsubstituted dibenzo-para-dioxin... . After... 59 wk... 24 male and 24 female mice... were still alive. None of treated mice had skin tumors... 1 female treated with unsubstituted dibenzo-para-dioxin had lymphoma.

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ ...Groups of 50 male and 50 female B6C3F1 mice were fed diets containing 0.5% or 1% unsubstituted dibenzo-para-dioxin... . Numbers of survivors /1%, 39th wk: 48/50 male mice, 29/50 female mice; 0.5%, 34th wk; 50/50 male mice, 39th wk, 49/50 female mice/... hyperplasia of bronchial mucosa... in 1 mouse fed 1% unsubstituted... .

/LABORATORY ANIMALS: Chronic Exposure or Carcinogenicity/ Mice treated with compounds including dibenzodioxin showed promotion of skin carcinogenesis induced by dimethylbenzanthracene.

For more Non-Human Toxicity Excerpts (Complete) data for DIBENZO-P-DIOXIN (6 total), please visit the HSDB record page.