Exposure of Agriculture Workers to Pesticides: The Effect of Heat on Protective Glove Performance and Skin Exposure to Dichlorvos.

Dichlorvos is a toxic organophosphate insecticide that is used in agriculture and other insecticide applications. Dermal uptake is a known exposure route for dichlorvos and chemical protective gloves are commonly utilized. Chemical handling and application may occur in a variety of thermal environments, and the rates of both chemical permeation through gloves and transdermal penetration may vary significantly with temperature. There has been no published research on the temperature-dependent kinetics of these processes for dichlorvos and thus, this study reports on the effects of hot conditions for the concentrated and application strength chemical. Dichlorvos breakthrough times for non-disposable polyvinyl chloride (PVC) gloves at 60 °C were approximately halved compared to 25 °C for the concentrate (2 vs. 4 h) and more than halved at application strength (3 vs. >8 h). From permeation experiments covering 15-60 °C, there was a 460-fold increase in cumulative permeation over 8 h for the concentrated dichlorvos and the estimated activation energy halved. Elevated temperature was also shown to be a significant factor for human skin penetration increasing the cumulative penetration of concentrate dichlorvos from 179 ± 37 to 1315 ± 362 µg/cm2 (p = 0.0032) and application strength from 29.8 ± 5.7 to 115 ± 19 µg/cm2 (p = 0.0131). This work illustrates the important role temperature plays in glove performance and health risk via dermal exposure. As such, it is important to consider in-use conditions of temperature when implementing chemical hygiene programs.

Chronic inhalation of 2, 2-dichlorovinyl dimethyl phosphate (DDVP) induces organ pathology in the adult albino rats

The acute toxic effects of the acetyl cholinesterase-inhibiting pesticide, DDVP, following oral and dermal exposure are well recorded in literature. The ability of DDVP to easily vaporize makes the aero-nasal route a possible means of exposure, albeit chronically. This study aimed to describe the pathology, if any, of the heart, kidney and liver following chronic exposure to various concentrations of DDVP via inhalation.Sixty male Wistar rats were divided into 6 groups (A-F) of 10 rats each. Rats in Group A were exposed to distilled water only, while rats in groups B, C, D, E and F were exposed to 20, 40, 60, 80 and 100% v/v concentrated fumes of DDVP respectively. Duration of inhalational exposure was for 90 days. The heart, liver and kidney of the rats in the groups were extracted for routine histopathology. Organ pathologies were semi-quantitatively scored and analyzed across and between the 6 groups.Generally, lesions were of progressive severity with increasing concentrations of DDVP. Across the organs, pathology was related to altered vascular and degenerative changes. Specifically, the heart, kidney and liver showed shredding of cardiomyocytes, sloughing of renal tubular epithelial cells with dilated tubular lumina, and hepatocellular degeneration and necrosis respectively. Inflammatory changes were limited to the livers of rats exposed to 80 and 100% v/v DDVP.It was concluded that DDVP induced altered vascular and degenerative changes following chronic exposure via inhalation. Safer alternatives to aerosolized DDVP-containing insecticides are recommended for the control of arthropod vectors in enclosures

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Fatal Poisoning with Both Dichlorvos and Phenthoate.

Organophosphates are widely used as pesticides. However, organophosphates are occasionally orally ingested to commit suicide. In this case, a man in his late 80s committed suicide by ingesting both dichlorvos and phenthoate. Autopsy findings revealed a characteristic volatile odor from his mouth, stomach, lungs, liver, and kidneys. The esophageal mucosa was denatured and had lost elasticity. Serum cholinesterase activity was 9 IU/L. Toxicological analyses performed using high-performance liquid chromatography-tandem mass spectrometry revealed that dichlorvos concentrations in the left and right cardiac blood samples were 11.6 and 4.6 µg/mL, respectively. Phenthoate concentrations in the left and right cardiac blood samples were 5.8 and 0.51 µg/mL, respectively. The total amounts of dichlorvos and phenthoate in the stomach were 7.35 and 4.55 g, respectively. The case history, autopsy findings, and toxicological analyses indicated that the cause of death was acute fatal poisoning after oral ingestion of both dichlorvos and phenthoate.

Cell cycle activation in p21 dependent pathway: An alternative mechanism of organophosphate induced dopaminergic neurodegeneration.

In the previous study, we demonstrated that dichlorvos induces oxidative stress in dopaminergic neuronal cells and subsequent caspase activation mediates apoptosis. In the present study, we evaluated the effect and mechanism of dichlorvos induced oxidative stress on cell cycle activation in NGF-differentiated PC12 cells. Dichlorvos exposure resulted in oxidative DNA damage along with activation of cell cycle machinery in differentiated PC12 cells. Dichlorvos exposed cells exhibited an increased expression of p53, cyclin-D1, pRb and decreased expression of p21suggesting a re-entry of differentiated cells into the cell cycle. Cell cycle analysis of dichlorvos exposed cells revealed a reduction of cells in the G0/G1 phase of the cell cycle (25%), and a concomitant increase of cells in S phase (30%) and G2/M phase (43.3%) compared to control PC12 cells. Further, immunoblotting of cytochrome c, Bax, Bcl-2 and cleaved caspase-3 revealed that dichlorvos induces a caspase-dependent cell death in PC12 cells. These results suggest that Dichlorvos exposure has the potential to generate oxidative stress which evokes activation of cell cycle machinery leading to apoptotic cell death via cytochrome c release from mitochondria and subsequent caspase-3 activation in differentiated PC12 cells.

A metabonomic analysis of the effect of quercetin on toxicity induced by chronic exposure to low-level dichlorvos in rat plasma.

A previous study of ours has reported that chronic exposure to low-level dichlorvos (DDVP, 7.2 mg per kg bw) damages the liver, interferes with fatty acid metabolism, and disturbs the antioxidant defense system in rats. This study aims to investigate whether or not quercetin can protect against DDVP-induced toxicity through metabonomics and to elucidate the mechanism underlying this protective effect. Rats were randomly assigned into the control group, DDVP-treated group, quercetin-treated group, and quercetin plus DDVP-treated group. DDVP and quercetin were administered to the rats daily via drinking water and gavage, respectively, continuously for 90 d. The metabonomic profiles of rat plasma were analyzed using ultra-performance liquid chromatography-mass spectrometry. Finally, 11 metabolites were identified, including those of quercetin, isorhamnetin, and quercetin-3-glucuronide. The 11 metabolites showed significant changes in some treatment groups compared with the control group. Arachidonic acid, phytosphingosine, and C16 sphinganine significantly decreased while p-cresol, lysoPE (16:0/0:0), lysoPC (15:0/0:0), lysoPC (16:0/0:0), lysoPC (0:0/18:0), and tryptophan significantly increased in the DDVP-treated group compared with the control group. The tendency of the aforementioned metabolites to change was significantly ameliorated in the high-dose quercetin (50 mg per kg bw per day) plus DDVP-treated group compared with the DDVP-treated group. However, the levels of these metabolites in the high-dose quercetin plus DDVP-treated group were still significantly different from those in the control group. The results indicate that high-dose quercetin (50 mg per kg bw per day) elicits a partial protective effect on DDVP-induced toxicity. The histopathology of the liver tissues was consistent with the above results. Quercetin demonstrated regulatory effects on the metabolism of lipids and amino acids, the antioxidant defense system, etc. Therefore, increasing the daily intake of quercetin can ameliorate the toxicity induced by chronic exposure to low-level DDVP residue in food and/or water.

Genotoxicity of dichlorvos in strains of Drosophila melanogaster defective in DNA repair.

Dichlorvos (DDVP), an organophosphate pesticide, is reported to be genotoxic at high concentrations. However, the roles of DNA damage repair pathways in DDVP genotoxicity are not well characterized. To test whether pre- and post-replication pathways are involved, we measured changes in DNA migration (Comet assay) in the midgut cells of Drosophila melanogaster Oregon R+ larvae and in some mutants of pre- (mei-9, mus201, and mus207) and post- (mei-41 and mus209)replication DNA repair pathways. Insects were exposed to environmentally relevant concentrations of DDVP (up to 15ng/ml) for 48h. After insect exposure to 0.15ng/ml DDVP, we observed greater DNA damage in pre-replication repair mutants; effects on Oregon R+ and post-replication repair mutants were insignificant. In contrast, significant DNA damage was observed in the post-replication repair mutants after their exposure to 1.5 and 15ng/ml DDVP. The pre-replication repair mutant mus207 showed maximum sensitivity to DDVP, suggestive of alkylation damage to DNA. We also examined mutants (SOD- and urate-null) that are sensitive to oxidative stress and the results indicate that significant oxidative DNA damage occurs in DDVP-exposed mutants. This study suggests involvement of both pre- and post-replication repair pathways against DDVP-induced DNA damage in Drosophila, with oxidative DNA damage leading to genotoxicity.

Anticonvulsant effect of Diazoxide against Dichlorvos-induced seizures in mice.

Dichlorvos, a synthetic organophosphate toxin, is used as pesticides. These toxins can be used as pesticides in farming and medicine for the devastation and/or elimination of ectoparasites of animals. Reports have shown that Dichlorvos generate seizure effects in various animals. Potassium channel opener is extensively used for medication of cardiovascular and other diseases. Studies have shown that potassium channel opener has anticonvulsant effects in different animal models. The goal of this study was to evaluate the effect of dizoxide on Dichlorvos-induced seizures in mice. In this research, the animals received different doses of Diazoxide (1, 2.5, 5, 10, and 20 mg/kg b.wt.) intraperitoneally 30 min before intraperitoneal injection of Dichlorvos (50 mg/kg b.w.t). After Dichlorvos injection, latency of clones, severity of seizure, and finally death as the fate were investigated. Results showed that Diazoxide dose-dependently decreased the severity of Dichlorvos-induced seizures, so that Diazoxide at a dose of 5 mg (the lowest, P < 0.05) and 20 mg/kg b.wt. (the highest, P < 0.001) has anticonvulsant effects. Thus, our data suggest that diazoxide as ATP-sensitive potassium channels opener has anticonvulsant activity against dichlorvas-induced seizure.

Baited traps may be an alternative to conventional pesticides in integrated crop management of chicory (Compositae) in South Africa.

Chicory, Chicorium intybus L. (Compositae), is a major field crop in the Eastern Cape Province of South Africa. Several pests feed on the leaves of the plant, resulting in reduced yield. The most important of these are the noctuid moths Helicoverpa armigera (Hübner), Chrysodeixis acuta (Walker), and Trichoplusia orichalcea (F.). The use of attract-and-kill traps offers an alternative to broad-based insecticides in the control of these species. Three fields were treated with normal insecticides and three fields with yellow-baited traps. Eight additional traps were placed in each field, with half of the traps containing the insecticide 2,2-dichlorovinyl dimethyl phosphate (dichlorvos) and half without dichlorvos; and half yellow and half green. Total moth numbers and nonphytophage diversity were measured from these eight traps. Although no differences in H. armigera or T. orichalcea catches were observed between insecticide- and trap-treated fields, numbers of C. acuta and the total number of moths were significantly higher in insecticide-treated fields. Yellow traps containing dichlorvos contained more moths than yellow traps without dichlorvos, or green traps with dichlorvos, or green traps without dichlorvos; but they also contained more nonphytophagous insects. Yellow traps also enhanced the catches of thrips on card traps associated with them. These results offer an opportunity for the South African chicory industry to reduce pesticide applications and thus mitigate environmental impacts.

Dichlorvos exposure and human cancer risk: results from the Agricultural Health Study.

OBJECTIVES: We evaluated cancer risk from DDVP (2,2-Dichloroethenyl dimethylphosphate) exposure among pesticide applicators enrolled in the Agricultural Health Study (AHS) cohort. METHODS: The AHS is a cohort of 57,311 pesticide applicators in North Carolina and Iowa, enrolled from 1993 to 1997 and followed for cancer through 2004. A comprehensive questionnaire collected information on exposure to DDVP and potential confounders. Among the 49,762 licensed pesticide applicators eligible for analysis, 4,613 reported use of DDVP. DDVP exposure was classified as intensity-weighted cumulative exposure days (IWED), calculated as [years of use x days per year x intensity level]. Poisson regression analysis was used to calculate rate ratios (RR) and 95% confidence intervals (CI) to evaluate the association of DDVP exposure among 2,943 incident cases of cancer. RESULTS: DDVP exposure was not associated with any cancer studied here. We observed no elevation in risk among lymphohematopoietic cancers, RR = 1.00 (95% CI 0.51, 1.96) and a small excess risk associated with exposure among those with a family history of prostate cancer (RR = 1.18 (95% CI 0.73, 1.82). CONCLUSION: We find little evidence of an association between cumulative lifetime use of DDVP and risk of any cancer at this stage of follow up of the AHS.

Aerial and tidal transport of mosquito control pesticides into the Florida Keys National Marine Sanctuary

This project was undertaken as the initial monitoring program to determine if mosquito adulticides applied along the Florida Keys cause adverse ecological effects in the Florida Keys National Marine Sanctuary (FKNMS). The study monitored the distribution and persistence of two mosquito adulticides, permethrin and dibrom (naled), during three separate routine applications by the Florida Keys Mosquito Control District. The approach was to determine if toxic concentrations of the pesticides entered the FKNMS by aerial drift or tidal transport. The amount of pesticide entering the FKNMS by way of aerial drift was monitored by collection on glass fiber filter pads, set on floats in a grid pattern on either side of the FKNMS. Permethrin was recovered from filter pads on the leeward side for each of the three applications, ranging from 0.5 to 50.1 microg/m(2) throughout the study. Tidal current transport was monitored by collection of surface and subsurface water samples at each grid site. Tidal transport of naled and dichlorvos (naled degradation product) was apparent in the adjacent waters of the FKNMS. These compounds were detected in subsurface, offshore water at 0.1 to 0.6 microg/1, 14 hr after application. Permethrin was not detected in offshore water samples; however, concentrations ranging from 5.1 to 9.4 microg/l were found in surface water from the canal system adjacent to the application route. Comparison of the observed environmental concentrations with toxicity data (permethrin LC-50, 96 hr for Mysidopsis bahia = 0.02 microg/l) indicated a potential hazard to marine invertebrates in the canals with possible tidal transport to other areas

Characterisation of cholinesterases and evaluation of the inhibitory potential of chlorpyrifos and dichlorvos to Artemia salina and Artemia parthenogenetica.

In this study, the acute toxicity of the organophosphorous pesticides dichlorvos and chlorpyrifos to two different species of Artemia (A. salina and A. parthenogenetica) was evaluated. In addition, the in vivo effect of these two pesticides on cholinesterase (ChE) activity of both A. salina and A. parthenogenetica was also determined. The characterisation of the ChE, using different substrates and specific inhibitors, and the normal range of activity in non-exposed individuals were previously investigated for both species. The results obtained indicate that the ChE of A. salina is different from that of A. parthenogenetica and that both enzymes cannot be classified neither as acetylcholinesterase nor as butyrylcholinesterase since they show intermediary characteristics between the two vertebrate forms. The range of normal ChE activity was 2.65+/-0.15 U/mg protein for A. salina, and 3.69+/-0.17 U/mg protein for A. parthenogenetica. Significant in vivo effects of both pesticides on Artemia ChE activity were found, at concentrations between 5.38 and 9.30 mg/l for dichlorvos and between 1.85 and 3.19 mg/l for chlorpyrifos. Both Artemia species are resistant to these pesticides and they are able to survive with more than 80% ChE inhibition. However, A. parthenogenetica is more resistant than A. salina, with about a 95% reduction in its ChE activity respect to the control for nauplii exposed to the median lethal concentrations (LC50), without lethal effects after 24 h of exposure.

Proposal for a method for testing resistance of clothing and gloves to penetration by pesticides.

The paper presents the proposal for a method for testing the resistance of materials used for the production of protective clothing and gloves to penetration by concentrated chemical preparations of pesticides. It has been based to a large extent on the recommendations of European standards, with certain modifications resulting from the specific properties of non-volatile and non-water-soluble biologically-active components of pesticides. These modifications primarily involved the use of a solid sorption medium and adjustment of research apparatus to the research conditions consistent with the proposed method. The results of preliminary studies on penetration of the selected biologically-active components of pesticides (dichlorvos, 2,4-D, cypermethrin, carbofuran) through the selected protective materials (fabric coated with viton and butyl on both sides, rubberised fabric, butyl rubber) are presented. The study confirmed the usefulness of the proposed method for testing the resistance of materials protecting against the effect of pesticides.

Effect of DDVP on the histology and AChE kinetics of heart muscles of Rattus norvegicus.

The LD50 of DDVP (Dichloro, dimethyl vinyl phosphate) for Rattus norvegicus was 21.4 mg/kg. b.w. The two sub lethal doses 1 and 3 mg/kg showed many histopathological changes in the working heart muscles and also showed significant necrosis in this S-A node, A-V node and bunble of His of the cardiac conducting system. These sublethal doses of the OP pesticide caused a significant inhibition of AChE. The maximum inhibition was noticed at the highest dose. The enhanced inhibitory constant Km and ACh contents in the heart muscles with the increase of dose showed inhibition of enzyme. The constant Vmax showed competitive nature of inhibition. A significant inhibition of AChE (69%) indicated that DDVP is a strong inhibitor of enzyme in heart.

[Dichlorvos insect strips indoors: pollution and risk assessment]. / Dichlorvos-Insektenstrips in Innenräumen: Belastung und Risikoabschätzung.

Exposure to Danger and Assessing the Hazards: Application of the highly potent pest control agent dichlorvos (DDVP) involves the hazard of effects on the central nervous system and a risk of human cancer. Consumers use dichlorvos in pest strips to protect their rooms from insects. This undifferentiated pest control can lead to chronic exposure. Over several weeks we found an indoor air concentration of dichlorvos between 60 and 1300 micrograms/m3 in 34 m3-experimental-room (chamber). Textiles and foodstuffs in this room were also contaminated. Beside the inhalative intake the oral and dermal intake can also lead to an additional loading of the residents. The ADI-resp. DTA-value of 4 micrograms/kg body-weight and day is exceeded about 10-15 times on the average by inhalative exposure only.

Use of household pesticides and the risk of aplastic anaemia in Thailand. The Aplastic Anemia Study Group.

BACKGROUND: Aplastic anaemia is a severe blood dyscrasia that is more common in Thailand than in Western countries. Its a etiology remains poorly understood. METHODS: A case-control study was conducted in Bangkok and two rural regions of Thailand. The effect of household pesticides was evaluated among 253 incident cases of aplastic anaemia and 1174 hospital controls. RESULTS: A total of 54% of the cases and 61% of the controls were exposed 1-6 months previously. For most individual household pesticides and for groups classified according to chemical type (organophosphates, pyrethrins, and organochlorines), the relative risk (RR) estimates approximated 1.0; upper 95% confidence limits were below 2.0 for many comparisons. A significant association was observed for exposure to combination products containing dichlorvos and propoxur, with an overall RR estimate of 1.7 (95% confidence interval [CI]: 1.1-2.6); the estimate for regular use was 1.6 (95% CI: 0.9-2.9). CONCLUSIONS: The absence of a higher risk for the regular use of dichlorvos/propoxur reduces the credibility of the apparent association, which could well have been an artefact of multiple comparisons. We conclude that most household pesticides used in Thailand do not appear to increase the risk of aplastic anaemia.

Delayed-type allergenicity of triforine (Saprol).

The delayed-type allergenicity of triforine (Saprol), 1,4-bis (2,2,2-trichloro-1-formamidoethyl) piperazine, was studied. In a mass examination of chrysanthemum growers among whom triforine was commonly used, the highest rate of positive patch test reaction was seen to triforine (17%) among the 7 pesticides and chrysanthemum extracts tested. A higher prevalence rate of work-related skin symptoms was seen in subjects with a positive patch test reaction to triforine (44%) than in those with negative reactions to all allergens tested (15%) (p < 0.05). 12 subjects (67%) with positive patch test reactions to triforine were also positive to dichlorvos (DDVP), with a high kappa coefficient (0.65). The grading of guinea pig maximization test to triforine was grade IV (66%), defined as "strong". Cross-sensitization between triforine and dichlorvos was also shown. The present results confirm that triforine is capable of including delayed-type allergy among chrysanthemum growers and of showing cross-reactivity with dichlorvos.