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

Cellular metabolism and health impacts of dichlorvos: Occurrence, detection, prevention, and remedial strategies-A review

Dichlorvos (2,2-Dichlorovinyl dimethyl phosphate, [DDVP]) belongs to the class of organophosphates and is widely used as an insecticide in agriculture farming and post-harvest storage units. Extensive research has been conducted to assess the factors responsible for the presence of DDVP in terrestrial and aquatic ecosystems, as well as the entire food chain. Numerous studies have demonstrated the presence of DDVP metabolites in the food chain and their toxicity to mammals. These studies emphasize that both immediate and chronic exposure to DDVP can disrupt the host's homeostasis, leading to multi-organ damage. Furthermore, as a potent carcinogen, DDVP can harm aquatic systems. Therefore, understanding the contamination of DDVP and its toxicological effects on both plants and mammals is vital for minimizing potential risks and enhancing safety in the future. This review aimed to comprehensively consolidate information about the distribution, ecological effects, and health impacts of DDVP, as well as its metabolism, detection, prevention, and remediation strategies. In summary, this study observes the distribution of DDVP contaminations in vegetables and fruits, resulting in significant toxicity to humans. Although several detection and bioremediation strategies are emerging, the improper application of DDVP and the alarming level of DDVP contamination in foods lead to human toxicity that requires attention.

Dimethoate absorption: A complementary in vitro and in vivo assessment

This work attempts to evaluate dermal exposure (DE) of farm workers to dimethoate after 4 h of routine application to a lemon plantation. Dimethoate was measured on the workers' clothes as well as in stratum corneum (SC) and in saliva. In vitro permeation tests (IVPT) were performed through rat, pig and human skin and pig buccal, esophageal and sublingual mucosas. The mean of dimethoate DE was 342.19 ± 487.14 mg/d, the percentage of toxic dose per hour was higher than the other pesticides, and the SC penetration factors ranged between 0.5 and 14.81 and 0.05-53.96 % for back of neck and arms respectively. In the supporting IVPT study, dimethoate absorption through human skin was 14.75 % and the default value in the absence of experimental data for this product is 70%. These results show that in family farming the deficiency of correct clothing during the application of pesticides leaves workers more vulnerable.

Olfactory dysfunction and potential mechanisms caused by volatile organophosphate dichlorvos in the silkworm as a model animal

Volatile pesticides impair olfactory function in workers/farmers and insects, but data on molecular responses and mechanisms are poorly understood. This study aims to reveal the mechanisms of olfactory dysfunction in the silkworm after exposure to volatile dichlorvos. Our results demonstrated that acute exposure for 12 h significantly reduced electroantennogram responses, and over 62.50% of the treated male moths cannot locate the pheromone source. Transcriptional and proteomic responses of the antennae and heads were investigated. A total of 101 differentially expressed genes (DEGs) in the antennae, 138 DEGs in the heads, and 43 differentially expressed proteins (DEPs) in the heads including antennae were revealed. We discovered that upregulations of Arrestin1 and nitric oxide synthase1 (NOS1) may inhibit cyclic nucleotide-gated channels and hinder calcium influx in the antennae. In the central nervous systems (CNS), downregulations of tyrosine hydroxylase (TH) and tyrosine decarboxylase (TDC) may inhibit olfactory signal transduction by reducing the second messenger biosynthesis. Meanwhile, an abnormal increase of brain cell apoptosis was revealed by Annexin V-mCherry staining, often leading to persistent neurologic impairment. Taken together, this study highlighted olfactory dysfunction caused by dichlorvos, which may provide a novel perspective for understanding the toxicity mechanism of volatile pesticides in other organisms.

Reassessment of the experimental skin permeability coefficients of polycyclic aromatic hydrocarbons and organophosphorus pesticides

Human exposure to polycyclic aromatic hydrocarbons (PAHs) and organophosphorus pesticides (OPPs) by dermal route is a continuing concern in environmental and occupational toxicology. Diverse authors have measured in vitro the absorption flux and permeability coefficient (k_P) of those compounds delivered on skin surface using volatile solvents. However, there isn't a harmonized method to obtain k_P when the test substance is deposited on the skin as a solid. Consequently, varied experimental k_Ps have been reported for PAHs and OPPs, most in clear disagreement with the values predicted by well-established mathematical models. In this work, we collected the permeation fluxes reported for these toxicants through human skin and calculated the (aqueous) k_Ps using a method based on the maximum flux and water solubility. The reanalyzed fluxes and recalculated k_Ps show improved consistency between the different experimental works and mathematical models. Notably, the recalculated k_P of benzo[a]pyrene, among others, was approximately 100 times higher than it had been previously considered. Suggestions are given to generalize the method in studies with other solvent-deposited toxicants and drugs.

Glove performance in a warming climate: The role of glove material and climate on permeation resistance to organophosphate insecticides

Hands and forearms are the principal sites of dermal exposure to organophosphate insecticides, which makes glove use one of the most important components of an exposure control strategy. However, the selection of suitable gloves depends on issues such as task, type, and concentration of organophosphate as well as cost. In addition, chemical protection performance of gloves may be temperature dependent, which is of increasing concern in a warming climate. Two recommended reusable glove materials (polyvinylchloride and nitrile butadiene rubber) and one single-use glove (nitrile/neoprene) were tested for permeation resistance to actual formulations of organophosphate insecticides with active ingredients dimethoate and malathion. Chemical resistance parameters were measured using American society for testing and materials permeation test cells and compared across glove, organophosphate type, and temperature. The three gloves demonstrated comparable and adequate chemical resistance (less than one µg cm^-2min^-1 for up to 8 hr exposure; 25-60 °C) for dilute forms of dimethoate and malathion, used during spraying activities. However, the single-use nitrile/neoprene glove is not designed to fully cover the elbow which limits its suitability. In permeation tests that reflect "worst case" exposure scenario to concentrated (neat) organophosphate formulations, as in mixing/loading tasks, a significant variation in chemical resistance between gloves was observed. While polyvinylchloride offered the maximum resistance, physical degradation of nitrile butadiene rubber after 3 hr of continuous exposure makes it unsuitable for handling neat dimethoate. The single-use nitrile/neoprene glove material had considerably poorer permeation resistance (up to 155-fold greater permeation and 6-fold shorter breakthrough) against neat formulations. Overall, elevated temperature (>40 °C) was shown to result in significantly greater (P < 0.05) cumulative permeation of neat formulation insecticides. This work demonstrates the variation in glove performance and potential for greater exposure risk particularly when mixing concentrated pesticides at elevated temperature conditions such as an occluded human skin or hot greenhouses. Training and guidance on testing, selection, use, and storage of gloves should consider in-use exposure scenarios and temperature-induced reduction in chemical protective performance.

Sublethal concentrations of dichlorvos and paraquat induce genotoxic and histological effects in the Clarias gariepinus

Non-target aquatic organisms such as fish may be impacted by agricultural activities through the run-off of pesticides from farms into aquatic ecosystems. In this study, the genotoxic (erythrocytic micronuclei) and histological effects of sublethal concentrations (1% and 10% of 96-h median lethal concentration (LC₅₀) values) of two pesticides (dichlorvos and paraquat) were evaluated in Clarias gariepinus (the African Sharptooth Catfish) for 28 days. The 96-h LC₅₀ of dichlorvos and paraquat against fingerlings of C. gariepinus was 730 μg/L and 50 μg/L, respectively. There was a significant dose-dependent increase (p<0.05) in micronuclei in the erythrocytes of exposed C. gariepinus (2.00±0.82 ‰ to 3.25±1.26 ‰ for dichlorvos and 2.25±0.96 ‰ to 4.75±0.96 ‰ for paraquat) compared to control (0.75±0.96 ‰) by day 28. Gill histological alterations such as mild to severe necrosis and blunting of secondary lamellae were observed in C. gariepinus exposed to higher sublethal concentrations of both pesticides. This study showed that non-target aquatic organisms like C. gariepinus may be at risk of adverse biological effects from exposure to pesticides from non-point sources. We recommend environmental monitoring and sensitization on responsible pesticide use to stakeholders. This will forestall potential adverse ecological effects in aquatic ecosystems.