M. A. Q. Khan

Protection against heavy metal toxicity by mucus and scales in fish

Fingerlings of three freshwater fish showed differences in susceptibility to lethality of 250 mg/L lead suspension or lead nitrate solution in water. Among these, the largemouth bass (Micropterus salmoides) was more tolerant than green sunfish (Lepomis cyanellus) and goldfish (Carassius auratus). The addition of mucus from largemouth bass, when added to jars containing lead, increased the LT-50 value (time to kill 50% of fingerling exposed to 250 mg/L lead) in green sunfish and goldfish. However, adding scales, especially if the scales were treated with an alkaline solution of cysteine and glycine, made all of these species tolerant to otherwise lethal concentrations of lead or mercury. The scales buffered the pH of lead nitrate solution as well as removed lead (and mercury) from water (by settling down at the bottom after sequestering lead). Scales of younger fingerlings of largemouth bass were more efficient in chelating heavy metals than those of older ones.

Toxicity-metabolism relationship of the photoisomers of certain chlorinated cyclodiene insecticide chemicals

Photoaldrin, photodieldrin, and photoheptachlor are more toxic than their corresponding parent compounds (aldrin, dieldrin, and heptachlor) to freshwater invertebrates and vertebrates, and to adult houseflies. The increase in toxicity is very significant in the case of the amphipod,Gammarus (1.5–12 times), bluegill fry (3.6–5.7 times), mosquito larvae,Aedas (2.3–6 times), minnow fry (2.5 times), and the isopid,Asellus (2 times). The greatest increases occur with photodieldrin which is 12 and 5 times more toxic than dieldrin, respectively, toGammarus, and to blue-gill fry, and with photoaldrin which is 6 and 4 times more toxic than aldrin, respectively, to mosquito larvae and bluegill fry. The toxicities of the photoisomers of isodrin and chlordene are generally less than those of their parent compounds to all the organisms tested. The basis of the differences in toxicities of the chlorinated cyclodiene photoisomers appears to be related to their chemical structure which possibly affects their action at the site(s) of toxic action and/or detoxication. The acidic proton present at the secondary chloride in photoaldrin, photodieldrin, and photoheptachlor possibly is responsible for the formation of charge-transfer complexes between components of the nerve and the mixed-function oxidase; the latter enzyme apparently dehydrochlorinates these photo products to their corresponding, more toxic ketones. The absence of such protons in photoisodrin and photochlordene renders them incapable of forming such ketones. The inhibition of these reactions by sesamex in house flies increases the stability of the chlorinated cyclodiene insecticides and, thus, significantly affects their toxicity. The conversion of photoaldrin, photodieldrin, and photoheptachlor to more-toxic and lipophilic ketones warrants additional studies of their accumulation and subsequent concentration by the food chain.

Photolysis of Heptachlor andcis-chlordane and toxicity of their photoisomers to animals

Heptachlor andcis-chlordane are converted to their corresponding photoisomers and several minor products on exposure to low intensity (longwave) ultra-violet light. This photolysis can also take place on plant leaves in the presence of sunlight or uv light. Photo-cis-chlordane and photoheptachlor are more toxic to fish. Photoheptachlor is about 20, 47, and 264 times more toxic than heptachlor to, respectively, rats, bluegill, and goldfish. Photo-cis-chlordane is about 10 times less toxic toDaphnia pulex.

Absorption and elimination of14C-alpha- andgamma-chlordane by a freshwater alga, daphnid, and goldfish

The bioconcentration of chlordanes by fresh water food chain organisms gave values of 5,560 for algae, 24,000 for daphnids, and 162 for goldfish. The transfer of preexposed daphnids and goldfish to insecticide-free water resulted in up to 90% elimination of the absorbed/adsorbed dose in 7 and 11 days, respectively. Tissue distribution of chlordane suggests that the biliary pathway of excretion, along with elimination through the gill, kidney, and feces, may be important in the elimination of lipophilic hydrocarbons by fish.

Oxidative dehydrochlorination of heptachlor by Daphnia magna

Abstract [14C]Heptachlor is metabolized by the freshwater microcrustacean, Daphnia magna, to 1-hydroxychlordene, 1-ketochlordene, 1-hydroxy-2,3-epoxychlordene, and their glucosides, sulfates, and other conjugates. 1-Hydroxychlordene is converted to 1-ketochlordene, indicating that in vivo formation of 1-ketochlordene may proceed via oxidative dehydrochlorination of HC-Cl in heptachlor to CHOH (1-hydroxychlordene) followed by oxidation of the latter to 1-ketochlordene. The ketone formation from heptachlor may not result via a chlorohydrin intermediate.

Metabolism of14C-heptachlor in goldfish (Carassius auratus)

Goldfish injected with14C-heptachlor (38.2 μg/44 g fish) eliminated about 18% of the dose in 10 days. Analyses of the fish at the end of 10 days revealed the presence of five compounds of which 91.2% was unchanged heptachlor and the remainder was heptachlor epoxide (5.4%), 1-hydroxychlordene (1.0%), 1-hydroxy-2,3-epoxychlordene (1.1%) and a conjugate (1.2%). The conjugate, on acid hydrolysis, yielded a product more polar than dihydroxyheptachlor, most likely a trihydroxy product. Analyses of feces and water showed the presence of only polar products.

Biotransformation and disposition of hexachlorocyclopentadiene in fish.

Fate of hexachlorocyclopentadiene (Hex) was studied in fresh-water fish usingin vivo andin vitro systems. Hex injected intraperitoneally into goldfish is readily distributed, stored and metabolized (>11 organosoluble and hydrophilic metabolites). The body radioactivity in tissues declines, but levels in bile remain high, indicating biliary excretion as a major route of elimination for Hex and its metabolites. Total radioactivity eliminated in water indicated three phases with a calculated half-life (t1/2) of 7 days and predicted 90 and 95% clearance of 162 and 211 days, respectively. A 3-segment straight line model gave the best fit of the elimination data. A compartmental model indicated two elimination and one reabsorption phase. For a static system, two phases of elimination were detected with a calculated t1/2 of 9 days and predicted 90 and 95% clearance of 77 and 107 days, respectively. A compartmental model indicted that one elimination and one reabsorption phase were involved.Goldfish produced a number of organosoluble and watersoluble metabolitesin vivo. Several of the organosolubles may be volatile, and at least 11 were characterized by thinlayer chromatography. The primary metabolites may react with endogenous molecules which render them more hydrophilic.Hepatic microsomal P-450 oxygenases and cytosolic GSH-transferases from bluegills may be involved in Hex metabolism. GSH can also alter Hex nonenzymically. The two hexane-extractable (in vitro) metabolites of Hex were more polar than Hex. The inhibitors of the microsomal P-450 oxygenase (piperonyl butoxide) and UDPGA-transferase (salicylamide) do not affect the toxicity of Hex to goldfish fingerlings, indicating that its toxicity may not be related to these pathways.

Biological magnification of photodieldrin by food chain organisms

Species differences were seen among fresh-water invertebrates and fishes in the absorption and subsequent retention of photodieldrin (a sunlight conversion product of the insecticide, dieldrin). The crayfishCambarus and the clamSimpsoniconcha showed extremely low levels of absorption and accumulation while the larvae of the mosquitoAedes, the amphipodGammarus, and the cladoceransSimocephalus, and fresh-water fleaDaphnia showed much higher levels of this insecticide. Maximum absorption occurred within 12 to 24 hours of exposure in only a few invertebrates but in most fishes. Among fishes, five to six times higher levels were seen during this period in guppy and goldfish than in minnow and bluegill. While the livebearer, guppy, kept absorbing photodieldrin with time, other fishes showed a slight decline in their tissue levels of this insecticide. The maximum biological magnification ratios during peak periods of absorption were: 133 for bluegill, 150 for minnow, 609 for goldfish, and 820 for guppy. Among microcrustacea the maximum biological magnification ratios seen after four days of continuous exposure were about 1000 forSimocephalus, 1200 forGammarus, and 63,000 forDaphnia. No appreciablein vivo metabolism of photodieldrin was seen in fishes, minnow and bluegill, and the decline in their body levels of photodieldrin is apparently not due to detoxication of the latter.

Lead content of soils along Chicago's Eisenhower and Loop-terminal Expressways

The lead content of soils along Chicagos two expressways, the Chicago Loop-terminal Expressway and the Eisenhower Expressway, have been determined in various seasons of the year and at various distances from the roadway. The concentration of lead in soils along the Chicago Loop-terminal Expressway and adjoining city streets show positive correlation (correlation coefficient = 0.988) with the average traffic volume near the sampling sites during the same season. The levels of lead in soils along the Eisenhower Expressway, at the same site, vary with the season; the lead levels are the least during fall and winter and they increase during spring and attain peak values during summer. This seasonal variation in the lead levels is similar to the seasonal variations in average monthly traffic volumes on the expressway. The soil contains as much as 7,600 parts per million of lead (micrograms per gram of dried soil) up to 45 feet and 900 parts per million up to 150 feet from the Eisenhower Expressway. There is a need to investigate the contamination of human beings that live or work in buildings within these distances from the expressways and wider buffer zones need to be provided along future expressways.

BIOTRANSFORMATIONS OF CYCLODIENES AND THEIR PHOTOISOMERS AND HEXACHLOROCYCLOPENTADIENE IN MAMMALS AND FISH

ABSTRACT Biotransformations of isomeric cyclodienes; cis -chlordane, cis -photochlordane; heptachlor, photoheptachlor; dieldrin, photodieldrin, endrin, and of hexachlorocyclopentadiene in mammals and fish are reviewed and salient metabolic pathways are outlined. There are differences in the degree of susceptibility of the isomers to biotransformations, e.g. (i) cis -photo-chlordane, photodieldrin, and photoisodrin are metabolized more efficiently than cis -chlordane, diel drin, and isodrin/endrin; (ii) endrin is metabolized more readily than dieldrin in these vertebrates. There are qualitative and quantitative differences among these vertebrates, both inter-species, and intra-species (sex, age), in the metabolism of the same chemical. Fish, as compared with mammals, are very slow in metabolizing these chemicals. An important aspect of these biotransformations is that these species can transform most of these toxicants to even more toxic and lipophilic products, e.g., Heptachlor to heptachlor epoxide, chlordane to oxychlordane, dieldrin and photodieldrin to ketodieldrin, and endrin to 12-ketoendrin and 12-hydroxyendrins. “Because of the common occurrence of these cyclodienes in human fat and environment and because non-human primates retain these insecticides longer than other mammals, these cyclodienes and their toxic metabolites may have more serious effects on human health and environment.” Since fish excrete these chemicals and their lipophilic metabolites more slowly than mammals they may serve as a repository of these extremely toxic and persistent lipophilic chemicals and their metabolites. Hexachlorocyclopentadiene is rapidly metabolized by rats, man, and fish. The products extracted from urine (where almost all of the recoverable administered radioactivity is found) and fish excreta and fish do not show any hexachlorocyclopentadiene. The products appear polyhydroxy and their conjugates along with unextractables.