Chapter 5 Dithiocarbamates

Protection of crop from fungal infestation is a major global concern in agriculture. There are several synthetic fungicides available on the market which are effective against a wide spectrum of fungal species. However, the existing fungicides show toxicity against nontarget organisms including human beings causing numerous health hazards. It is important to generate awareness among people coming in direct contact with these chemicals occupationally to prevent fungicide-induced diseases in the communities. Exposure to fungicides during their application in crop fields through spraying devices, the residues of these hazardous chemicals enter the body through nasal and dermal routes. However, environmental impact and risk associated with the use of fungicides as an agrochemical has received little attention across the globe. The ecotoxicological aspect of several widely used fungicides has not been investigated in terms of their adverse health impact on living beings and ecological functioning. Accumulation of these diverse fungicides in environmental compartment like air, water, and soil can pose threat to the communities. In this chapter, we discuss the diverse classes of fungicides and their effects on nontarget living being in various ecosystems. Attempts have also been made to elaborated the bio-fungicides based of phytochemicals and their advantages over synthetic fungicides.

A mixed-ligand nickel(II) dithiocarbamate complex of the composition [Ni(bpdtc)(PPh₃)₂]ClO₄·PPh₃ was synthesized, characterized (elemental analysis, UV–Vis, IR and NMR spectroscopy and molar conductivity measurements) and its X-ray structure was determined. The three ligands are arranged in a distorted square-planar geometry (an S₂P₂ donor set), with the bond lengths and angles within the vicinity of the central atom as follows: NiP = 2.2150(6) and 2.2529(6) Å, NiS = 2.2267(6) and 2.2129(6) Å, PNiP = 105.11(2)°, SNiS = 78.26(2)°. The PNiP angle of the studied complex falls outside the interval of 98.37–102.92° determined for thirteen formerly reported structural analogues involving the [Ni(ndtc)(PPh₃)₂]⁺ moiety with a combination of dithiocarbamate (ndtc) and triphenylphosphine (PPh₃) ligands. In the crystal, the complex cations, perchlorate anions and PPh₃ molecules of crystallization are linked through intramolecular CH⋯O and CH⋯π and intermolecular CH⋯O, CH⋯C and CH⋯π contacts to a three-dimensional architecture.

Exposure to mercury can lead to several injuries in mammals, including immune system dysfunction, and pyrrolidine dithiocarbamate (PDTC), as a metal chelator and antioxidant, has been indicated to increase the cytotoxic effects of toxic metals. However, the toxicological effects and possible mechanisms of mercury in combination with PDTC are mostly unclear. In this study, we showed that PDTC dramatically increase the cytotoxic effect of HgCl₂ on cultured murine macrophages (RAW 264.7 cells). PDTC augmented HgCl₂-induced cytotoxic effects by facilitating the entry of mercury into the cells. The Hg²⁺/PDTC complex significantly and rapidly increased the formation of reactive oxygen species (ROS) and decreased intracellular glutathione (GSH) levels in these cells. Flow cytometry analysis showed that the numbers of sub-G1 hypodiploid cells and annexin V-FITC binding cells increased after Hg²⁺/PDTC complex exposure, and several features of mitochondria-dependent apoptosis were also induced, including mitochondrial membrane depolarization, cytosolic cytochrome c release, poly(ADP-ribose) polymerase (PARP) and caspase 3/7 activation, and DNA fragmentation. Moreover, both apoptotic and necrotic cells were detected using acridine orange/ethidium bromide dual staining. Meanwhile, depleted intracellular ATP levels and increased lactate dehydrogenase (LDH) release were observed, suggesting the induction of necrotic cell death processes. These Hg²⁺/PDTC complex-induced cytotoxicity-related signals could be reversed by pretreatment with the antioxidant N-acetylcysteine. In conclusion, these results suggest that Hg²⁺/PDTC complex-induced oxidative stress causes macrophage cell death via both apoptosis and necrosis. These findings imply for the first time that PDTC dramatically increases the uptake and toxicological effects of Hg²⁺ instead of detoxification.

Les dithiocarbamates constituent une famille de pesticides antifongiques largement utilisée en France. Cette étude s’est intéressée aux opérateurs exposés aux spécialités commerciales à base d’éthylène-bis-dithiocarbamates en viticulture, horticulture et culture de pommes de terre.

Quantifier l’exposition par une mesure de l’excrétion urinaire du principal métabolite, l’éthylènethiourée (ETU), et corréler les résultats aux pratiques observées.

Le protocole a associé l’étude des comportements des applicateurs dont les pratiques étaient observées par un médecin du travail ou un conseiller de prévention et le dosage de l’ETU avant (le matin du jour de l’observation) et après exposition (48 heures à 96 heures après la fin de l’exposition de ce jour d’observation).

Une élévation significative (p = 0,0001) du taux d’ETU est constatée avec une médiane des taux urinaires avant exposition de 0,43 μg/g de créatinine et de 2,62 μg/g de créatinine après exposition. Seule l’efficacité du masque lors de la préparation a pu être démontrée en matière de protections individuelles (p = 0,012) montrant dans ce cas la part prédominante de la contamination par voie respiratoire. À l’inverse, un effet préjudiciable de l’onychophagie est observé (p = 0,043). Ces deux constats peuvent être expliqués par la formulation en poudre très fine inhalable des spécialités commerciales. Par ailleurs, la cabine de tracteur fermée aurait également un effet protecteur, résultat déjà observé lors d’une étude précédente.

Cette étude démontre l’intérêt d’une approche ergoexpologique pour une réelle évaluation et compréhension du risque professionnel lié à l’exposition à des substances chimiques en mesure d’orienter les alternatives en prévention primaire.

Dithiocarbamate fungicides are widely used in France. This study investigated winegrowing, horticulture and potato-farming workers exposed to commercial products containing ethylenebisdithiocarbamates.

To quantify exposure by measuring urinary excretion of the main metabolite, ethylenethiourea (ETU), and correlate the results with observed work practices.

The protocol comprised observation of the worker's spraying technique by an occupational health physician or a prevention consultant and ETU determination before (in the morning of the day of observation) and after exposure (48 h to 96 h after the end of exposure on the day of observation).

A significant elevation (p = 0.0001) of ETU levels was observed with a median urinary ETU level of 0.43 μg/g of creatinine before exposure and 2.62 μg/g of creatinine after exposure. The only significantly effective individual protective measure was the use of a mask during preparation (p = 0.012), indicating the predominant role of respiratory tract contamination. In contrast, nail-biting was shown to have a negative impact (p = 0.043). These two findings can be explained by the very fine inhalable powder formulation of commercial products. A closed tractor cabin also appeared to have a protective effect, as already observed during a previous study.

This study demonstrates the value of an occupational toxicology approach to provide a real evaluation and understanding of the occupational risk related to exposure to chemical substances in order to guide primary prevention measures.

Neurological complications as well as movement disorders are relevant symptoms in animals and humans chronically exposed to dithiocarbamates. Using rat pheochromocytoma cells differentiated by NGF (PC12), we investigated whether propineb affects acetylcholine (Ach) release and the molecular mechanisms involved. Propineb (0.001–100 nM) dose-dependently increased Ach release from PC12. Thus, 0.001–1 nM propineb-induced Ach release, reaching a maximal effect (∼50%) at 0.1–1 nM. Higher concentrations of propineb (10–100 nM) caused a progressive disappearance of the effect. Chelation of extra- and intracellular Ca²⁺ did not affect Ach release by propineb, which was prevented by the actin stabilizer jasplakinolide (500 nM). Accordingly, actin depolymerization was observed after exposure of differentiated PC12 to 0.1–1 nM propineb, a loss of effect was evident at higher concentrations (100 nM), and the effect was Ca²⁺-independent. Disulfiram, a related dithiocarbamate not coordinated with Zn²⁺, also depolymerized actin, suggesting the involvement of the organic structure of dithiocarbamates rather than the leakage of Zn²⁺. Nevertheless, propineb did not depolymerize actin in a cell-free system.

These data suggest that dithiocarbamates, through the activation of intracellular cascade(s), impair cytoskeletal actin. This effect may contribute to affect synaptic vesicles processing resulting in an impaired cholinergic transmission.

This is a newly developed method which permits the quantitative determination of 2-thiazolidinethione-4-carboxylic acid (TTCA, an established biomarker of exposure to CS₂) as a metabolite of alkylene bisdithiocarbamates (ABDCs) in human urine. After separation of TTCA from the urinary matrix using liquid–liquid extraction the analyte was converted into its diethyl derivative. Separation and quantitative analysis was carried out by capillary gas chromatography and mass selective detection in single ion monitoring mode. 4-(4-Chloro-2-methylphenoxy)butanoic acid (MCPBA) served as internal standard. The detection limit was 0.7 μg/l in urine. The relative standard deviation of the within-series imprecision was 4.3% at a concentration of 13 μg/l. The relative recovery was within the range of 86 to 98%. In order to determine the suitability of TTCA for biological monitoring after exposure to ABDCs, we analysed 87 24-h urine samples from occupationally exposed workers. The results were compared with the levels of TTCA excreted in urine by 50 control persons without known exposure to dithiocarbamates or CS₂. This collective of unexposed persons also provided TTCA reference values for the general population. The urinary TTCA concentrations of the exposed persons were in the range from 0.8 μg/g creatinine to 515 μg/g creatinine. Unexposed persons excreted TTCA in concentrations from below the detection limit to 182 μg/g creatinine. The median concentration found in exposed persons (27 μg/g) was nearly 2.5 times higher than in non-exposed persons (11 μg/g). The difference between the exposed and unexposed collective was highly significant. Assessment of an individual’s exposure by determining the level of TTCA in urine nevertheless was not possible. This was due to the relatively wide range of concentrations and because the ranges of both collectives overlapped.