Air pollutants formed in thermal decomposition of folpet fungicide under oxidative conditions

Evaluation of metabolic stress status in common carp (Cyprinus carpio) exposed to the fungicide folpet

Among pesticides, fungicides are the most extensively used ones in agriculture and their effects on fish health and indirectly human health are needed to evaluate. Folpet has been used for over 50 years as a fungicide across the world. The mechanism of action of folpet on non-target aquatic organisms is so poorly understood and there is no available information about potential acute toxicity of folpet and its mechanism of action in non-target aquatic organisms. With this motivation, two successive experiments were set up: first, 96 h-LC₅₀ value of folpet for common carp (Cyprinus carpio) was determined; and second, effects of different sublethal concentrations (0, 0.025, 0.50, 0.1 and 0.15 mg/L) of folpet on hematological serum biochemical blood parameters, DNA damages, expression levels of catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GPx), glutathione S-transferase (GST), and cortisol receptor (HSP70) genes were evaluated in this study. It was calculated that 0.199 mg/L of folpet was the 96 h-LC₅₀ value. After the folpet exposure for 14 days, significant decreases in red blood cells, hemoglobin, hematocrit, serum total protein, and GST gene expression levels were observed while serum glucose, liver enzymes activities, and expression levels of CAT, SOD, GPx, HSP70 genes increased. Also, folpet induced a significant genotoxic effect on the blood cells regarding to DNA damages. Consequently, the results have shown the toxic effects of folpet even at the lowest concentration on common carp.

Atmospheric oxidation of Folpet initiated by OH radicals, NO3 radicals, and O3

The fate of Folpet is dictated by oxidation initiated by atmospheric oxidants such as O₃, OH, and NO₃ radicals. Considering the oxidant concentration in the atmosphere, Folpet seems to be mainly scavenged by NO₃ radicals, especially at night.

Toxic pollutants emitted from thermal decomposition of phthalimide compounds

Phthalimide (PI) and tetrahydrophthalimide (THPI) are two structurally similar compounds extensively used as intermediates for the synthesis of variety of industrial chemicals. This paper investigates the thermal decomposition of PI and THPI under oxygen rich to oxygen lean conditions, quantifying the production of toxicants and explaining their formation pathways. The experiments involved a plug flow reactor followed by silica cartridges, activated charcoal trap and a condenser, with the decomposition products identified and quantified by Fourier transform infrared spectroscopy (FTIR), gas chromatography-mass spectrometry (GC-MS) and micro gas chromatography (μGC). The density functional theory (DFT) calculations served to obtain dissociation energies and reaction pathways, to elucidate the reaction mechanism. The oxidation of PI and THPI produced several toxic nitrogen-containing gases and volatile organic compounds, including hydrogen cyanide, isocyanic acid, nitrogen oxides, benzonitrile, maleimide and tentatively identified benzenemethanimine. The detection of dibenzo-p-dioxin (DD) and dibenzofuran (DF) suggests potential formation of the toxic persistent organic pollutants (POPs) in fires involving PI and THPI, in presence of a chlorine source. The oxidation of THPI produced 2-cyclohexen-1-one, a toxic unsaturated ketone. The results of the present study provide the data for quantitative risk assessments of emissions of toxicants in combustion processes involving PI and THPI.