Fish amphibians and reptiles

Tumors in English sole (Puget Sound, WA), Medeka, and other species may be due to their exposure to HHCs along with polycyclic aryl hydrocarbons (PAHs). In addition to this, mortality of hatchlings (fry), adult survival, and reproductive effects (feminization) may occur. The decline in frog populations and their hind leg and other deformities have been assumed to be related with HHC pesticides. Alligators exposed to DDE and PCBs have been reported to show atrophy of their testes causing lowering of testosterone and feminization.

Table 7 A list of commonly used halogenated hydrocarbons and their toxicities to D. magnaa

LCn^r1)

Alkanes

Methyl chloride

Methyl bromide, methyl iodide

1,2-Dichloromethane

Ethyl iodide, ethyl bromide

1.1-Dichloropropane

1.2-Dichloropropane

1.3-Dichloropropane n-Butyl chloride Vinyl chloride

Vinyl bromide 2-Chloro-n-propane

1.2-Dichloro-p-propane Chlorobromomethane Trichloromethane 1,1,2-Trichloroethane

1.1.1-Trichloroethane Hexafluoropropane Tetrachloromethane Tetraiodomethane Dichlorofluoromethane 1,1,1,2-Tetrachloroethane 1,1,2,2-Tetrachloroethane 1,1,2,2,2-Pentachloroethane Hexachloroethane

Alkenes

1.3-Dichloropropene Tetrachloroethene Vinylidene chloride Hexachloropropene

Alkynes

1,1-Dichloroethylene trans-1, 2-Dichloroethylene

1.1.2-Trichloroethylene Methylene chloride Tetrachloroethylene cis-1,2-Dichloroethylene 1,1,2-Trichloroethylene Monohaloethylenes Tetrafluoromethylene Chlorotrifluoromethylene

1.1-Dichloro-2,2-difluoroethylene Chlorotrifluoroethylene 2-Chloroethanol 2,2,2-Trichloroethanol

Halogenated aromatics Chlorobenzene

1.2-Dichlorobenzene

1.4-Dichlorobenzene

1.3-Dichlorobenzene

1.2.4-Trichlorobenzene

1.2.5-Tetrachlorobenzene Pentachlorobenzene

Chlorinated phenols

2-Chlororophenol 4-Chlorophenol

3-Chlorobiphenyl 2-Chlorobiphenyl

2.4-Dichlorophenol

23 52 280

198 70 530

24 41 12 0.006

6 14

135 220 51

Table 7 (Continued)

HHC

LCsoißgl-1)

3,4,5-Trichlorophenol

0.68

2,4,6-Trichlorophenol

3.03

2,4,5-Trichlorophenol

2.70

2,3,4,6-Tetrachlorophenol

0.29

Tetrachlorophenol

0.41

2,4,5,6-Tetrachlorophenol

0.56

Pentachlorophenol

0.73

Pentachlorophenol-sodium

0.40

Hexachloro-1, 3-butadiene

Hexachlorocyclopentadiene

Pesticides

Dichlorovos

0.004

2,4-Dichlorophenoxyacetate

0.83

Picloram

59

Trichloropropane

0.117

Chloramp

212

Chloroxuron

2.95

Lindane

0.899

Dibenzofuran

0.005

DDT

0.003

Chloropheniphos

0.043

Endosulfan

0.283

Permethrin

0.002

aData from Adams WJ, Champan GA, and Landis WG (eds.) (1988) Aquatic Toxicology and Hazard Assessment, Vol. 10. 579pp. Philadelphia: ASTM.

aData from Adams WJ, Champan GA, and Landis WG (eds.) (1988) Aquatic Toxicology and Hazard Assessment, Vol. 10. 579pp. Philadelphia: ASTM.

Water birds

Residues of HHCs in food and water of water birds has contaminated and affected fish-eating birds' reproduction (feminization of males, nest abandonment, ineffective incubation). This has been observed in Great Lakes Region in cormorants, terns, raptors, and other species, and in local and migratory waterfowl in Lake Michigan, Green Bay, Long Island Sound as well as in Adeline penguins and south polar skua. In Lake Michigan Basin, hatchling failure and malformations and sex reversal in male double-crested cormorants have been noticed. Foster tern eggs contain very high levels of PCBs leading to embryotoxicity, aberrant parental behavior, and hormonal changes. High concentration of DDT, dieldrin, and PCBs dangerously reduced the number of raptors in North America and Britain and seriously affected their reproduction in the Great Lakes region.

Sea mammals

In St. Lawrence Seaway, whales/seals contain high concentrations of PCBs and PAHs, which are high in sediments: concentrations of PCB (180 ppm) in male belugas and in blubber of young ones (270 ppb) (young ones showing metastasized bladder carcinoma and males with other tumors). Juvenile females had about 600 ppm PCB in blubber. Mink whales from the Antarctic contained PCBs, HHCs, HCB, and DDT in blubber and food. Baltic seals are also contaminated with PCBs and DDT. Females with

Table 8 Oral toxicity of TCDD in mammals

LD50 tpgkg1 body wt.)

Animal Average of male and female

Table 8 Oral toxicity of TCDD in mammals

Animal Average of male and female

Guinea pigs

0.6-2.1

Rat

22-45

Mice

283

Rabbit

115

Monkey

50-70

Hamster

100

LD50 values (mg kg-1) for male rats for DDT, dieldrin, Toxaphene, dichlorovos, and lindane are 113, 46, 90, 80, and 200, respectively. Data from Kimbrough RD (1981) Chronic toxicity of halogenated biphenyls and related compounds in animals and health effects. In: Khan MAQ and Stanton RH (eds.) Toxicology of Halogenated Hydrocarbons, pp. 23-37. New York: Pergamon.

LD50 values (mg kg-1) for male rats for DDT, dieldrin, Toxaphene, dichlorovos, and lindane are 113, 46, 90, 80, and 200, respectively. Data from Kimbrough RD (1981) Chronic toxicity of halogenated biphenyls and related compounds in animals and health effects. In: Khan MAQ and Stanton RH (eds.) Toxicology of Halogenated Hydrocarbons, pp. 23-37. New York: Pergamon.

high concentrations of DDT and its metabolites showed pathological changes in their uteri. Those with high PCBs had implantation failure and adrenal cortex atrophy. California sea lions have also shown reproductive disorders (premature birth), immune suppression, gastric and intestinal ulceration, and liver, skin, and kidney lesions, which are also seen in adult beluga whales.

Land mammals

In Michigan, mink and ferret populations fed PBB/ PCB-contaminated lake fish showed reproductive failure, induction of P450 in hepatocytes, degenerative renal changes, anorexia, gastric ulcers, loss of hair, and enlargement of liver, pancreas, and adrenals. The toxicities of various HHCs to experimental mammals (Table 8) indicate the severity of TCDD and its related coplanar chlorinated aryl hydrocarbons. Species-specific differences in sensitivity to these HHCs are very prominent (Table 9). In rats, dietary intake of PCBs for 130 days showed no symptoms at 0.001 mg kg~ d~ (=0.13 mg kg~ ), but a 10 times higher dose reduced fertility in two to three generations and a 100 times higher dose affected neonatal survival. A 2-year dietary exposure (0.1 mgkg-1 d^1) of rats caused several chronic effects, such as wasting, fatty liver, lung lesions, hypothyroidism, chloracne, liver cancer, and mortality.

Humans

While adult humans can be exposed to HHCs through dermal absorption, inhalation, and dietary intake, the neonates can be exposed as fetuses in utero and via breast milk. Embryos, fetuses, infants, and young children are more sensitive than adults.

Clinical exposure of children to chloroform, dichlor-omethane, ethyl chloride, trichloroethane, and halothane is closely watched.

Table 9 Toxic effects of some commonly used HHCs in rodents

Effect

TCDD

PCB

PBB

Chloronaphthalenes

LD50: mgkg-1

0.004-0.01

4000-10000

21 500

0.011-2000

Liver

Porphyria

+

+

+

+

Necrosis

+

-

-

Atrophy

Vit. A deficiency

-

+

-

+

P450 induction

+

+

+

Tumors

+ (+ Lung)

+

+

+ (+ Lung)

Immune suppression

In mice

-

+

+

Hyperkeratosis

In rabbit ear

+

+

+

+

Embryo toxicity

+ (+ Neonate, postnatals)

+

+

Neonates

Data from Kimbrough RD (1981) Chronic toxicity of halogenated blphenyls and related compounds In animals and health effects. In: Khan MAQ and Stanton RH (eds.) Toxicology of Halogenated Hydrocarbons, pp. 23-37. New York: Pergamon.

Data from Kimbrough RD (1981) Chronic toxicity of halogenated blphenyls and related compounds In animals and health effects. In: Khan MAQ and Stanton RH (eds.) Toxicology of Halogenated Hydrocarbons, pp. 23-37. New York: Pergamon.

Table 10 A list of HHCs, which have tested positive for carcinogenicity

System

Nonmutagenic carcinogenicity1

Tumors

Chlorobenzilate Chloroform Carbon tetrachloride Dieldrin

P, P'-Dichlorodiphenyl dichloroethylene Lindane PCB TCDD

Trichloroethylene 1,2-Dichloroethane

1,2-Dibromoethane

1,2-Dibromo-3-chloropropane

Hexachloroethane

Tetrachloroethylene

1,1,2-Trichloroethane

Rat liver Rat/mouse liver Rat/mouse Mouse liver Mouse liver

Mouse liver Rat/mouse liver Rat liver, lung Mouse liver

Kidney, thyroid, liver Liver

Liver

Subcutaneous, stomach, blood vessels, mammary gland Subcutaneous, stomach, blood vessels, lung Stomach, mammary gland Liver Liver Liver

The effects of halogenated aromatics (PCBs, PCDDs, PCDFs) depend on the type of the compound. They cause acute irritation of eyes, mucus membranes, lungs, and gastrointestinal tract besides affecting nervous systems. These also cause acne (chloracne), liver dysfunction, porphyria, and malignancies (Table 9) and exert developmental effects. Chlorinated toluenes (benzyl and benzal chlorides, benzotrichloride) are group 2A carcinogens. Other HHCs with carcinogenic potential are listed in Table 10.

PCDD residues are widely distributed, especially in aquatic environment, fish, and fish-eating birds and mammals. Their residues in human food (Table 11 ) can have significant chronic effects, especially in the presence of other HHCs. TCDD causes several symptoms of toxicity, such as wasting, fatty liver, lung lesions, hypothyroidism, chloracne, liver cancer (Tables 9 and 10). TCDD-linked cancer has been reported in factory workers in the form of brain cancer and malignant melanomas. PCDF congeners are not as toxic as PCDDs. A list of effects in experimental mammals is summarized in Tables 9 and 10.

The daily dietary intake of TCDD in humans (about 118 pg (TEQ) in North America and the Netherlands) is mostly via meats, fish, eggs, milk, and other dairy products (Table 11 ). There is a federal warning about the consumption of Lake Michigan fish by pregnant women and those expecting pregnancy and of fish in Lake Michigan Basin by children and young adults. The high concentrations of these HHCs in human breast milk have advisories against breast-feeding of infants. In utero exposure to HHC has shown newborn and children and young adults exhibit neurobehavioral deficits, which become more severe with age.

Table 11 PCDD and PCDF levels in food consumed in USA

Food

Conc. (pg/g fresh wt) Toxic equivalent

Beef

0.48

Pork

0.26

Chicken

0.19

Eggs

0.13

Dairy products

0.36

Milk

0.07

Fish

1.2

The residues of stable/persistent and toxic pesticides used in past are still present in global ecosystems and humans. Their presence in human breast milk has created concerns about effects in neonates leading to neurobeha-vioral deficits in children and young adults. It will take several decades for their residues to completely disappear. Their residues are still biomagnified in top carnivores. These HHCs are nerve and liver toxins. The LD50 of DDT to mammalian species ranges between 113 and 450mg/kg body wt. and that of cyclodienes between 40 and 60 mg/kg body wt.

Environmental products of cyclodiene insecticides (aldrin, dieldrin, heptachlor, chlordanes), namely their corresponding photoisomers, can become more toxic than the corresponding parent chemical and can be metabolized to even more toxic products. These toxic metabolites result from epoxidation of unsaturated bonds or oxidative dehydrochlorinations.

The metabolite of DDT, DDE, is more persistent in environment than DDT and is esterogenic. Methoxychlor, also, has estrogenic effects. DDD, a contaminant in DDT, causes adrenocorticoid atrophy.

PCBs have very low water solubility (3-21 mgl- ). Individual congeners with chlorine substitution in ortho-position on both rings vary in their persistence, stability, and toxicity. Coplanar PCBs have chlorine in ortho-position on both rings, such as 3,3',4,4'-tetrachlorobiphenyl. Planars have chlorine substitutions in 2-, 3-, or 4-ortho-positions, which moves rings out of phase because of interactions with adjacent chlorines in different rings. These have globular structures. PCBs are persistent and poorly metabolized in biota and thus are biomagnified in ecosystems harming top carnivores. Their half-life in humans varies from 30 days to 10 years. PCBs are transferred to offspring through the placenta and via milk. They cause neurobehavioral deficits in neonates due to their exposure i» utero as fetuses. Birth defects and lowering of male sex hormones (testicular atrophy) are reported in several bird and mammalian species. PBBs are used as fire retardants (Fire master) and resemble PCBs in their effects. TCAB and TCAOBs are immunosuppressive agents and may even affect anterior pituitary secretion of ACTH.

See also: Reproductive Toxicity.

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  • Yvonne
    How 2,2,2trichloroethanol is harmful to fish?
    7 years ago

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