Toxicity evaluation of metal plating wastewater employing the Microtox assay: a comparison with cladocerans and fish

The relative sensitivity of the Microtox assay is closely related to the type of toxicant, and hence its utility in biomonitoring effluents is better evaluated on a case-by-case basis. The Microtox assay, employing the marine bacterium Vibrio fischeri, was evaluated for its applicability in monitoring metal plating wastewater for toxicity. The results of the Microtox assay after 5, 15, and 30 min of exposure, were compared with data obtained from conventional whole effluent toxicity testing (WET) methods that employed Daphnia magna, Ceriodaphnia dubia, and the fathead minnow (Pimephales promelas). The Microtox assay produced notably comparable EC50 values to the LC50 values of the acute fathead minnow toxicity test (< 0.5 order of difference). The Spearman's rank correlation analyses showed that the bacterial assay, regardless of exposure duration, correlated better with the acute fish than the daphnid results (p < 0.05). These observations were consistent to other studies conducted with inorganic contaminants. The relative sensitivity of the 30-min Microtox assay was within the range of the two frequently used acute daphnid/fish toxicity tests. In conclusion, the Microtox assay correlated well with the acute fathead minnow data and is well suited for toxicity monitoring for these types of industrial wastes.

Acute and chronic life cycle toxicity of acenaphthene and 2,4,6-trichlorophenol to the midge Paratanytarsus parthenogeneticus (Diptera: Chironomidae)

The acute and life cycle toxicities of acenaphthene and 2,4,6-trichlorophenol (2,4,6-TCP) were evaluated using the parthenogenic dipteran larva, Paratanytarsus parthenogeneticus, of the family Chironomidae. Static 48 h acute toxicity tests employed third instar larvae, and the flow-through 20-day life cycle tests were initiated with eggs. No acute lethal effect was observed in the saturated concentration (2.1 mg/l) of acenaphthene in water, and the median lethal concentration of 2,4,6-TCP was approximately 40 mg/l. In the life cycle toxicity test with acenaphthene, hatchability of the midge was affected by 50% at an exposure concentration of approximately 0.17 mg/l. The median effective concentration for larval, pupal and adult development was found between 0.06 and 0.07 mg/l, respectively, and these were significantly lower than the effective concentration for hatching success. With regard to 2,4,6-TCP toxicity, the median effective concentration for midge hatchability was 4.23 mg/l. The larval development, pupal formation and adult emergence, however were impeded at 1.60, 1.46 and 1.33 mg/l, respectively. Each level was noticeably lower than the median effective concentration for hatchability. The concentrations for each compound that interfered with the development to fourth instar, pupa and adult were not significantly different. These results indicate that larval developments after hatching were the most sensitive stages and affected the success of midge growth.

Kinetics of acid-catalyzed degradation of cyclosporin A and its analogs in aqueous solution

The kinetics and mechanism of the degradation of cyclosporin A have been studied under aqueous acidic conditions. The rate of degradation was found to be specific acid-catalyzed over the pH range studied (1-4), with isocyclosporin A as the predominant degradation product. Selective reduction of the olefinic bond of the amino acid 2-N-methyl-(R)-((E)-2-butenyl)-4-methyl-L-threonine (MeBmt) did not affect the overall degradation kinetics and product distribution of cyclosporin A. These observations indicate that the alternative degradation pathway involving intramolecular alkoxy addition to the olefinic bond of amino acid MeBmt apparently does not significantly contribute to the overall degradation kinetics of cyclosporin A in the pH range 1-4. The chemical reactivity of O-acetyl-cyclosporin A was examined to probe the governing mechanism for the isomerization of cyclosporin A. Under identical conditions, O-acetyl-cyclosporin A showed a much greater chemical stability than cyclosporin A, consistent with a mechanism involving the hydroxyoxazolidine intermediate. The chemical stability of cyclosporin C, which contains two beta-hydroxyl groups, was also examined. The rate and product distribution for the degradation of cyclosporin C suggest that under aqueous acidic conditions it undergoes N,O-acyl migration solely at the amino acid residue MeBmt. Additionally, the impact of side-chain bulkiness of amino acid MeBmt was examined by studying the degradation kinetics of a series of cyclosporin A analogs.(ABSTRACT TRUNCATED AT 250 WORDS)

Organochlorine pesticide residues in paddy fish in Malaysia and the associated health risk to farmers

Paddy fish (Trichogaster pectoralis Regan) were collected from five sampling locations in a major paddy-growing area of Malaysia and analysed for organochlorine residues. During the same period, ten farming families, chosen at random from each of the five sampling sites, were interviewed. Information was obtained about the quantity of paddy fish consumed, the amount and type of pesticide used on the paddy-field, and the frequency of application.The pesticide residues found in the fish samples were aldrin/dieldrin, chlordane, HCH, and DDT. Only the projected maximum intake level for aldrin/dieldrin approached the acceptable daily intake as recommended by FAO/WHO; other residue levels were relatively low. However, this study considered only fish; the total daily intake of pesticide residues by the Malaysian paddy farmer may be considerably increased by consumption of other contaminated food.