Inhibition of brain AChE in brook trout by aminocarb and its toxic metabolites.

In-vitro inhibitions of brain AChE in brook trout, Salvelinus fontinalis (Mitchill), by aminocarb (4-dimethylamino-m-tolyl N-methylcarbamate) and its toxic metabolites, MAA (4-methylamino-m-tolyl N-methylcarbamate), AA(4-amino-m-tolyl N-methylcarbamate), MFA (4-methylformamido-m-tolyl N-methylcarbamate) and FA (4-formamido-m-tolyl N-methylcarbamate) were investigated. The molar concentrations of inhibitors causing 50% inhibition (I50s) were AA (3.62 X 10(-6] less than MAA (7.92 X 10(-6] less than aminocarb (1.01 X 10(-5] less than MFA (4.29 X 10(-5] less than FA (7.11 X 10(-5]. After exposure of fish to various concentrations of aminocarb (25, 250 and 2500 ppb) and MAA (25, 250, 500 and 2500 ppb) at 9 degrees C in dechlorinated tap water for 96 h, inhibitions of brain AChE ranged from 13 to 77%. Mortality occurred only in fish exposed to 500 ppb (22%) and 2500 ppb (100%) of MAA. Enzyme activities recovered to the control levels 12 to 96 h after the fish had been transferred to clean water for clearing; in survivors of the 500-ppb MAA exposure, however, AChE activities decreased again thereafter.

Disappearance of dimethoate, methamidophos and pirimicarb in lettuce.

Foliar sprays of dimethoate at 150 or 300 g a.i./ha, methamidophos at 450 or 900 g a.i./ha and pirimicarb at 140 or 280 g a.i./ha were applied for control of the green peach aphid, Myzus pericae (Sulzer), and the lettuce aphid, Nasonovia ribisnigri ( Mosley ), about 2 weeks before the lettuce started heading, and again about 1 week from harvest. In lettuce, dimethoate partially oxidized to its oxon and pirimicarb converted to its methylamino- and/or formyl methylamino-analogues. Most residues were present in the outer leaves which were exposed directly to the sprays; only traces of residues were detected in samples of the inner head leaves. Total residues disappeared rapidly. Pirimicarb was the least persistent and only traces of residues (less than 0.01 ppm) were detected in marketable heads. Concentrations of dimethoate, including the oxon and of methamidophos were well below their respective tolerances of 2 and 1 ppm respectively.

The lethal toxicity of Matacil 1.8 F to rainbow trout and its in vivo metabolism.

Fingerling rainbow trout (Salmo gairdneri Richardson) were used to determine the lethal toxicity of Matacil 1.8 F and Matacil 1.8 D ready-to-use formulations. The 96-h LC50s were 21.3 mg/l for water-based Matacil 1.8 F; 19.1 mg/l for oil-based Matacil 1.8 F; and 0.36 mg/l for Matacil 1.8 D. Aminocarb (4-dimethylamino-m-tolyl N-methylcarbamate) and MA (4-methylamino-m-tolyl N-methylcarbamate) were detected in fish tissue 96 h after exposure. More than 50% of the total residue (Aminocarb + MA) were the parent compound. The bioaccumulation ratio ranged from 1.70 to 3.32 at different concentrations of aminocarb. Both aminocarb and MA were rapidly eliminated after the fish had been transferred to clean water; the total residue declined by more than 90% in 72 h and became non-detectable in 96 h.

Simplified method for the analysis of some carbamate insecticides in foliage, forest soil and fish tissue by direct gas-liquid chromatography.

A simplified and sensitive method for the analysis of eight carbamate insecticide residues in foliage, forest soil and fish tissue by direct gas-liquid chromatography (GLC) is described. After fortification, the carbamate residues were extracted from the natural substrates by homogenization in ethyl acetate. The interfering co-extratives present in the crude extracts were removed by filtration through Whatman GF/A glass microfibre after coagulation. The carbamate residues were re-extracted into dichloromethane and directly analyzed intact by GLC with a Tracor Model 702 nitrogen-phosphorus detector. The rate of recovery for aminocarb, carbofuran, carbaryl, methomyl, mexacarbate, pirimicarb and propoxur was better than 80% at 5.0-ppm and 0.50-ppm levels. Slightly less than 60% was recovered for methiocarb.

Residues in cutthroat trout (Salmo clarki) and California newts (Tarichia torosa) from a lake treated with technical chlordane.

The water of a lake was sprayed with technical chlordane to give a concentration of approximately 10 ppb. Resident California newts (Tarichia torosa) and cutthroat trout (Salmo clarki) were subsequently collected and analyzed for residue concentrations. The newts were collected at 14, 279, 451, and 1,036 days; the trout at 93, 279, 421, and 1,014 days. At first, the concentrations of residues were very high in both species and their composition, except for heptachlor, resembled that of technical chlordane. The heptachlor was quantitatively epoxidized in news after 14 days but in trout, some heptachlor was still present after 93 days. Concentrations of total chlordane in body tissues of both species declined more than 98% with time. Of seven individually determined constituents of technical chlordane, trans-nonachlor was by far the most persistent, accounting for 49 to 55% of total chlordane in specimens collected last. Both animals produced oxychlordane, probably from gamma-chlordane. Heptachlor, heptachlor epoxide and gamma-chlordeine were non-detectable in both species after 279 days. The results strongly suggest that the California newt metabolizes and eliminates chlordane residues more effectively than the cutthroat trout.

Evaluation of Amberlite XAD-2 as the extractant for carbamate insecticides from natural water.

A rapid and sensitive analytical technique to quantify carbamate insecticides at nanogram levels is reported using resin column and sorption, and desorption followed by N-P gas-liquid chromatography (GLC) analysis. The carbamates were extracted from natural water by percolation through a column of Amberlite XAD-2, followed by elution with ethyl acetate. The carbamate residues were directly analyzed by GLC with a Tracor Model 702 N-P detector. The recoveries for several carbamates including aminocarb, mexacarbate, carbaryl, propoxur, carbofuran, pirimicarb and methiocarb were from 86 to 108% at 1.0 and 0.01 ppm levels. Only 41 to 58% was recovered for methomyl. The extraction efficiency of Amberlite XAD-2 was pH-dependent as indicated in the extraction of aminocarb. More than 90% of the added aminocarb was recovered from phosphate buffer by the described method at pH 5.0 to 7.5 at 5.0 and 0.5 ppm levels.

The fate of acephate and carbaryl in water.

Acephate was resistent to hydrolysis in distilled, buffered water at pH 4.0 to 6.9, but not at pH 8.2, held for 20 days at 20 or 30 degrees C. The maximum conversion to methamidophos was 4.5% of the added acephate at pH 8.2 and 20 degrees C. The persistence of acephate in two natural waters, held at 9 degrees C for up to 42 and 50 days varied: 80% were recovered from pond water after 42 days, and 45% from creek water after 50 days. Rates of acephate degradation increased greatly when treated water samples were incubated in the presence of sediments, but not if water and sediment were autoclaved prior to treatment and incubation. The greatest conversion to methamidophos, 1.3% of the added acephate, had occurred after 42 days in pond water without sediment. Under the same conditions, carbaryl was less persistent than acephate in the natural waters: 18 to 20% were recovered from pond water after 42 days, and 37 to 40% from creek water after 50 days. The presence of sediment did not affect its degradation significantly. But more than 55% were recovered after 50 days if water and sediment were autoclaved prior to treatment and incubation. Neither acephate, methamidophos, nor carbaryl could be shown to escape from water into the atmosphere.

A study on the lethal toxicity of aminocarb to freshwater crayfish and its in vivo metabolism.

Adult crayfish (Orconetes limosus) were exposed to 0.1, 1.0, 5.0, 10.0, 25.0, 30.0, 40.0, 50.0 and 60.0 ppm of aminocarb in water at 15 degrees C under laboratory conditions for 144 h. No apparent behavioral changes were observed in crayfish exposed to 0.1, 1.0 and 5.0 ppm of aminocarb during the experiment. Symptoms of acute toxicity were apparent at concentrations greater than or equal to 10 ppm, and mortality occurred at and above 25 ppm. The LC50, 96 h, to adult crayfish was about 33 ppm. The parent compound and its metabolites, MA (4-methylamino-m-tolyl N-methylcarbamate) and AM (4-amino-M-tolyl N-methylcarbamate), were detected in crayfish 96 h after exposure to various concentrations of aminocarb. The primary metabolite detected was MA which accounted for 75% to 95% of the body residue. The highest total residue (Aminocarb + MA + AM) was 40 ppm detected in crayfish exposed to 60 ppm of aminocarb for 96 h.

Persistence of residues in water and sediment of a fresh-water lake after surface application of technical chlordane.

A fresh-water lake, free from detectable pesticide residues before this study, was treated with a commercial formulation of technical chlordane. Water and sediment samples were analysed for chlordane residues 7, 24, 52, 279. and 421 days after treatment. Residues moved rapidly from the water to the lake bottom, supporting earlier results of a laboratory study with other organochlorines. In water, alpha- and gamma-chlordane concentrations remained proportional to total chlordane concentrations, as determined by total-peak area measurements of gas-liquid chromatogrammes. But in bottom sediments, alpha- and gamma-chlordane were more persistent than other constituents of technical chlordane, supporting recent evidence that quantification of technical chlordane residues on the basis of gamma-chlordane quantification only (or that of alpha- and gamma-chlordane only), can lead to incorrect results and that this method, although simple and fast, should no longer be recommended.

Chlorinated hydrocarbon residues in fish, crabs, and shellfish of the Lower Fraser River, its estuary, and selected locations in Georgia Strait, British Columbia--1972-73.

Between August 1972 and September 1973, fish, crabs, and shellfish were collected from the lower Fraser River, its estuary, and selected areas of Georgia Strait in British Columbia. Samples were analyzed for aldrin, dieldrin, alpha- and gamma-chlordane, p,p'-DDT, p,p'-DDE, p,p'-DDD, heptachlor, heptachlor epoxide, lindane, and polychlorinated biphenyls (PCB's). Of these, p,p'-DDT, p,p'-DDE, p,p'-DDD, heptachlor epoxide, and one PCB, Aroclor 1254, were detected in samples of many fish, crabs, and shellfish from the lower Fraser River and its estuary. Generally, compounds found in decreasing order of magnitude in samples from the Fraser River and its estuary were: PCB's, p,p'-DDE, heptachlor epoxide, p,p'-DDT, and p,p'-DDD. Greatest concentrations of these compounds occurred in biota from the waters adjacent to the City of Vancouver. With one exception, animals from Georgia Strait and those away from the immediate influence of Fraser River water contained no detectable levels of chlorinated hydrocarbons.