Biodegradation of beta-cypermethrin by a novel Azoarcus indigens strain HZ5

A novel strain HZ5 was isolated from the activated sludge of a pesticide manufacturer in Hangzhou, which was capable of degrading beta-cypermethrin (beta-CP). Based on its physiological characteristics and analysis of 16S rDNA gene, strain HZ5 was identified as Azoarcus indigens, which was a new genus that can degrade beta-CP effectively. Strain HZ5 could degrade beta-CP over a wide range of temperature (20 to 40°C) and pH (5.5 to 9.0), and the optimal temperature and pH were 30°C and 7.0. The highest degradation rate was approximately 70% of 50 mg/L beta-CP within 144 h at pH 7.0 and 30°C in MSM. An additional carbon source could enhance the biodegradation of beta-CP. Studies on biodegradation of the beta-CP showed no significant enantioselectivity. During the process, two main intermediate metabolites were produced by strain HZ5 and determined as 3-phenoxybenzaldehyde and 3-phenoxybenzoic acid by gas chromatography-mass spectrometry (GC-MS) analysis. The results indicated that strain HZ5 may have potential application in bioremediation of beta-CP polluted environment.     

Effect of ozonization in degradation of trifluralin residues in aqueous and food matrices

Abstract

This study investigates the oxidation of trifluralin residues during ozonation in aqueous and food matrices (tomato). Domestic ozonation equipment with average production of 23.9?mg O₃ L^?1 h^?1 was used in the tests. Modern chromatographic systems (SPME-GC-IT/MS/MS and QuEChERS-GC-IT/MS/MS) were applied for extraction and detection of trifluralin residue in fortified samples of ultrapure water, tap water, superficial water and tomato fruit. The samples were submitted to the ozonation process during 0, 5, 10 and 20?min. Treatment at 5?min was able to degrade 71.5% of herbicide trifluralin in surface water. The removal (%) in ultrapure water reached 83.4% after 20?min of ozonation. The degradation of trifluralin in fortified tomato samples (0.025–0.1?mg kg^?1) were conducted with ozonation at 20?min, and it ranged from 84.4 to 92.7%. After treatment, levels of trifluralin in tomato remained within the established MRLs to EU, USEPA and ANVISA (Brazil). The data provided evidence that ozone is effective for removing trace trifluralin from water and foods.     

Clinical effects and cholinesterase activity changes in workers exposed to phorate (Thimet)

Abstract

Phorate (Thimet), an aliphatic derivative of phospnorus is a hignly toxic insecticide. In order to implement the safety measures, the clinical manifestations and cholinesterase (ChE) activity were evaluated before and after 2 weeks of exposure to this insecticide in 40 male tormulators.

The 2 week's exposure reveal signs and symptoms of toxicity in 60% of the formulators. Gastrointestinal symptoms and lowering of heart rate (bradycardia) were more prominent as compared to the neurological symptoms. A significant depression in plasma ChE activity was observed at the end of 1st week (55%) and 2nd week (71%) as compared to the respective pre‐exposure values. A recovery up to 79% of the pre‐exposure activity of this enzyme was noticed 10 days after cessation of the above exposure.     

Deposition of aerially sprayed mexacarbate on balsam fir canopy and the forest floor: Relevance to ULV applications

Abstract

Spray deposit patterns were measured on aluminum coils and live balsam fir needles at different canopy heights, following aerial application of mexacarbate (4‐dimethylamino‐3,5‐xylyl N‐methylcarbamate) over a conifer forest in New Brunswick. Droplet size spectra of the spray cloud were determined on cylindrical Kromekote® cards placed at the corresponding crown heights. Ground deposits were collected on cylindrical Kromekote cards, aluminum coils and natural balsam fir foliage placed In forest clearings and under different types of vegetation.

Canopy deposits decreased progressively from the top to the bottom level of the tree crown. This trend was observed on aluminum coils, live fir foliage, and Kromekote cards. Droplet size spectra were similar at all sampling heights of the tree crown, and were comparable to those obtained on the ground cards placed in the forest clearings. Deposits of mexacarbate obtained on ground samplers on the open forest floor were markedly lower than those found at the top canopy but were similar to those at the mid or bottom canopy level. Droplet size spectra and mexacarbate deposits obtained on samplers placed under different types of forest vegetation indicated a selective filtration of the large droplets present in the spray cloud by plant canopies.     

Persistence and biodegradation of carbaryl in soils

Abstract

The persistence of the methylcarbamate pesticide carbaryl was studied in four soils under flooded conditions. A substantial portion of the pesticide was recovered from all soils even after 15 days of its application, with the recovery ranging from 37% in an alluvial soil to 73% in an acid sulfate soil. The degradation of carbaryl was more rapid under flooded conditions than under nonflooded conditions. A bacterium, Pseudomonas cepacia, isolated from a flooded soil amended with a related methylcarbamate pesticide carbofuran, degraded carbaryl in a mineral medium supplemented with yeast extract.     

Measurements of surface contamination of spray equipment with pesticides after various methods of application

Abstract

A traditional method to determine operator dermal exposure is to quantify the amount of pesticide coming into contact with specific body regions and then to integrate the deposition density values with the total body surface. It is known that extremely high deposition values may occur in the hand region; however, the source of contamination is generally assumed to be direct splash or contact with the pesticide container. One of the parameters affecting operator/pilot exposure could be the transfer of pesticide residue, particularly in the case of pesticides with a longer half‐life, from contaminated surfaces of spray equipment by direct contact over extended periods. If the rate of skin absorption of pesticide is readily known, the expected values of daily dose for an operator or pilot may significantly rise due to the extended contact period. This study produced field data on the surface contamination of spray equipment used for ground and aerial applications. If field data on precise work practice (time‐motion) observations are incorporated, it may be possible to estimate the potential exposure of operator/pilot due to hand contact with contaminated surfaces.     

Effect of maternal dietary hexachlorocyclohexane exposure on pup survival and growth in albino rats

Abstract

In adult albino rats, maternal dietary. ß‐ and ?‐hexachlorocyclohexane (HCH) intake during gestation upto 400 ppm level did not affect the number of litters produced. But about 50 and 100% pup mortality was found in 200 and 400 ppm ß ‐HCH group within 5 days of birth. Maternal mortality was observed in 800 ppm ß ‐HCH group during third week of gestation. The effect of maternal dietary intake of HCH isomers at 50 and 250 ppm level during gestation and/or lactation on perinatal development was also studied. The body weights and sizes of the newborn litters of mother rats exposed to dietary HCH isomers did not. differ from controls. Similarly, the growth and development of the litters of HCH exposed mother rats that survived 28 day lactation period were found to be comparable to controls as evidenced by the body weight and weight of vital organs. However, liver weight increases were found in the 28 day weaned litters wherever the mothers had been exposed to HCH isomers during lactation. Lowered kidney weight was seen in litters of mother rats fed 250 ppm ?‐HCH during gestation and lactation. The brain and testis weights were not affected in the litters of any experimental groups.     

Toxic effects of carbofuran and glyphosate on semen characteristics in rabbits

Abstract

The present study was undertaken to investigate the effect of chronic treatment with two sublethal doses of Carbofuran (carbamate insecticide) and Glyphosate (organophosphorus herbicide) on body weight and semen characteristics in mature male New Zealand white rabbits. Pesticide treatment resulted in a decline in body weight, libido, ejaculate volume, sperm concentration, semen initial fructose and semen osmolality. This was accompanied with increases in the abnormal and dead sperm and semen methylene blue reduction time. The hazardous effect of these pesticides on semen quality continued during the recovery period, and was dose‐dependent. These effects on sperm quality may be due to the direct cytotoxic effects of these pesticides on spermatogenesis and/or indirectly via hypothalami‐pituitary‐testis axis which control the reproductive efficiency.     

Effects of synthetic pyrethroids and methidation on activities of some digestive enzymes in carp (Cyprinus carpio L.)

Abstract

The effects of pyrethroid pesticides (deltamethrin, permethrin and cypermethrin) and an organophosphate ester (methidation) on the activities of carp trypsin, α‐chymotrypsin, carboxypeptidase A and lipase were studied. The enzymes were isolated from the gastrointestinal tract and the effects of the pesticides were investigated during incubation for 5 min. The activity of trypsin was influenced only slightly by the presence of deltamethrin and methidation, whereas permethrin and cypermethrin caused significant inhibition. The pyrethroid pesticides at lower concentrations resulted in a slight activation of α‐chymotrypsin. Methidation inhibited the α‐chymotrypsin activity by about 20%. These pesticides modified the lipase activity to a lesser extent; the highest inhibition was measured with cypermethrin. The carboxypeptidase A activity was inhibited by both pyrethroid pesticides and methidation. The results suggest that these pesticides might interact with the active conformation of the studied hydrolytic enzymes, resulting in changes in their activities.     

Minimizing drift and exposure from knapsack sprayers

Abstract

An improved drift shield for attaching to the lance of conventional knapsack sprayer to reduce wind induced drift and operator exposure was designed and tested. The drift shield consists of a conical wire frame covered with polythene and has an annular opening at the point of attachment to the lance which allows air to be drawn into the shield while spraying. Tests conducted with winds in the range of 1.25–5.75 m/s show that wind can increase the width of spray swath from an unshielded lance, up to 4.3 times the normal swath in no‐wind condition. Use of a conventional shield contained the swath width within 3.5 times and the improved shield restricted the swath width to 3.1 times the normal swath. Spray deposit from an unshielded lance, within the normal swath decreased to as low as 45%, due to wind effects. However, use of the conventional, and the improved shields enhanced the spray deposit to 54.2% and 68%, respectively. The improved drift shield improved the spray pattern displacement (SPD) significantly (P<0.05) compared with the conventional shield and the unshielded lance when the wind speed exceeded 1.25 m/s. The improved shield decreased the off target drift by as much as 63% compared with the unshielded spray. It also decreased the quantity of pesticide deposit on the operator's body by 41–84% and thereby reduced exposure and improved safety.