The treatment of soil infested with the human whipworm, Trichuris trichiura.
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The soil fumigants methyl bromide, chloropircrin and Basamid or mixtures of Basamid and chloropicrin proved to be of no use in filling T. trichiura ova in soil. However, on untreated plots the eggs died at a rate such than only 20% of the ova remained viable after 18 months. (+info)
Personal air sampling and biological monitoring of occupational exposure to the soil fumigant cis-1,3-dichloropropene.
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OBJECTIVES: To assess exposure of commercial application workers to the nematocide cis-1,3-dichloropropene (cis-DCP). METHODS: The study was conducted during the annual application season, August to 15 November, in the starch potato growing region in The Netherlands. 14 Application workers collected end of shift urine samples on each fumigation day (n=119). The mercapturic acid metabolite N-acetyl-S-(cis-3-chloro-2-propenyl)-L-cysteine (cis-DCP-MA) in urine was used for biological monitoring of the cis-DCP uptake. Inhalatory exposure was assessed by personal air sampling during a representative sample (n=37) of the fumigation days. Extensive information was collected on factors of possible relevance to the exposure and the application workers were observed for compliance with the statutory directions for use. The inhalatory exposure during all fumigation days was estimated from the relation between the personal air sampling data and the biological monitoring data. Exposure levels were correlated with the general work practice. The fumigation equipment and procedures were in accordance with the statutory directions of use, with the exception of the antidrip systems. Two antidrip systems were used: antidrip nozzles or a compressed air system. RESULTS: The geometric mean exposure of the application workers was 2.7 mg/m(3) (8 hour time weighted average); range 0.1-9.5 mg/m(3). On 25 days (21%) the exposure exceeded the Dutch occupational exposure limit (OEL) of 5 mg/m(3). This could mainly be explained by prolonged working days of more than 8 hours. The general work practice of the application workers was rated by the observers as good or poor. No difference in exposure to cis-DCP was found in the use of none, one, or two antidrip systems. Malfunctioning of the antidrip systems and lack of experience with the compressed air system were identified as possible causes for the lack of effectiveness of these antidrip systems. The use of personal protection was not always in accordance with the statutory directions of use. Dermal exposure to liquid cis-DCP was found four times during repair and maintenance, but the biological monitoring data did not suggest a significant increase in cis-DCP uptake. CONCLUSIONS: The application of cis-DCP in the potato growing industry can be performed at exposure concentrations below the Dutch OEL of 5 mg/m(3) if the working days are limited to 8 hours. An injector equipped with either kind of antidrip system which is in good working order, as well as the consistent use of personal protection in accordance with the statutory directions of use, may ensure exposure concentrations below the Dutch OEL. (+info)
Occupational exposure to cis-1,3-dichloropropene: biological effect monitoring of kidney and liver function.
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OBJECTIVES: To investigate the possible effects of occupational exposure to the nematocide cis-1,3-dichloropropene (cis-DCP) on function of the kidney and liver in the starch potato growing region in The Netherlands. METHODS: The study involved 13 commercial application workers exposed to cis-DCP for 117 days, and 22 matched control workers. The inhalatory exposure of the application workers was estimated from biological monitoring data. All workers collected urine and serum samples before, during, and after the fumigation season for monitoring of variables for kidney and liver function. Renal effect variables were alanine aminopeptidase (AAP), N-acetyl-beta-D-glucosaminidase (NAG), retinol binding protein (RBP), and albumin (ALB) in urine, and beta(2)-microglobulin (beta(2)M-S) and creatinine in serum (Creat-S). Liver variables were alanine aminotransferase (ALAT), aspartate aminotransferase (ASAT), gamma-glutamyltranspeptidase (GGT), alkaline phosphatase (ALP), and total bilirubin (TBIL) in serum and the urinary ratio of 6-beta-hydroxycortisol to free cortisol (betaOHC/COR). RESULTS: The geometric mean exposure of the application workers was 2.7 mg/m(3) (8 hour time weighted average (8 hour TWA)); range 0.1-9.5 mg/m(3). No differences were found between the values of the renal effect variables or the liver variables of the exposed group and the control group, except a lower urinary ratio of betaOHC/COR in the exposed group. This was not considered to be related to the exposure to cis-DCP. No dose-effect relations were found between the exposure indices and the effect variables. CONCLUSIONS: The present study does not provide evidence that occupational exposure to cis-DCP in the starch potato growing region causes adverse effects on the kidney or liver at 8 hour TWA exposure concentrations below 9.5 mg/m(3) (2 ppm). (+info)
Glucosinolate breakdown products as insect fumigants and their effect on carbon dioxide emission of insects.
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BACKGROUND: Glucosinolate breakdown products are volatile, therefore good candidates for insect fumigants. However, although they are insecticidal, the mode of action of such natural products is not clear. We studied the insecticidal effect of these compounds as fumigants, and monitored the production of carbon dioxide by the insects as a probe to the understanding of their mode of action. RESULTS: The fumigation 24-h LC50 against the house fly (Musca domestica L.) of allyl thiocyanate, allyl isothiocyanate, allyl cyanide, and l-cyano-2-hydroxy-3-butene was 0.1, 0.13, 3.66, and 6.2 microg cm-3, respectively; they were 0.55, 1.57, 2.8, and > 19.60 microg cm-3, respectively, against the lesser grain borer (Rhyzopertha dominica Fabricius). The fumigation toxicity of some of the glucosinolate products was very close to or better than that of the commercial insect fumigants such as chloropicrin (LC50: 0.08 and 1.3 microg cm-3 against M. domestica and R. dominica, respectively) and dichlorovos (LC50: < 0.02 and 0.29 microg cm-3 against M. domestica and R. dominica, respectively) in our laboratory tests. Significantly increased CO2 expiration was found in insects exposed to the vapor of allyl isothiocyanate, allyl thiocyanate and allyl isocyanate. Allyl isothiocyanate was also found to increase the CO2 expiration of the American cockroach (Periplaneta americana L.). CONCLUSIONS: Glucosinolate breakdown products have potential as biodegradable and safe insect fumigants. They may act on the insect respiratory system in their mode of action. (+info)
Experiments on terminal disinfection by formaldehyde vapor in the case of smallpox.
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The usually recommended terminal disinfection by formaldehyde vapor is unable to completely inactivate vaccinia viruses embedded in scabs. In view of our results, we recommend doubling the concentration of formaldehyde (10 g of formaldehyde per m3 of space) and prolonging the time of exposure to 24 h for terminal disinfection in the case of smallpox. Subsequent disinfection by scrubbing assumes special importance, since no complete inactivation of the scabs occurs. (+info)
Influence of elevated CO2 and O3 on Betula pendula Roth crown structure.
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Elevated CO(2) and ozone effects were studied singly and in combination on the crown structure of two Betula pendula clones. Measurements were made at the end of the second fumigation period in an open-top-chamber experiment with 9-year-old trees. Shoot ramification (number of long and short daughter shoots), shoot length, and number of metamers, leaves and buds were measured at four positions in every tree. As a result of increased temperature, trees in chambers had longer shoots and more frequent shoot ramification than control trees not enclosed in chambers. Ozone treatment decreased shoot ramification significantly. Additionally, ozone treatment resulted in an increased number of metamers in one clone. There was no statistically significant interaction between ozone effect and crown position; however, there was a slight tendency for the lower crown to be more affected by ozone. Elevated CO(2) caused a significant increase in the number of long-shoot metamers. Therefore, 2x ambient CO(2) concentration partly ameliorated the negative effect of ozone because the increased number of leaves per shoot counteracted the decreased branching. Although the main effects of elevated ozone and CO(2) were similar in the two clones, slight, statistically insignificant, differences appeared in their responses when interactions with crown position were considered. (+info)
Dimethyl disulfide exerts insecticidal neurotoxicity through mitochondrial dysfunction and activation of insect K(ATP) channels.
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The plant-derived insecticides have introduced a new concept in insecticide research. In response to insect attacks, some plants can release volatile sulfur compounds such as dimethyl disulfide (DMDS) in the atmosphere, which are lethal for the generalist insects. We demonstrate that DMDS induced an uncommon complex neurotoxic activity. The studies of in vivo toxicity of DMDS in three insect species and mice indicated a highest bioactivity for insects. Although DMDS did not alter the electrophysiological properties of the cockroach Periplaneta americana giant axon, it affected the synaptic transmission at the presynaptic level resulting in an inhibition of the neurotransmitter release. Whole cell patch-clamp experiments performed on cockroach cultured dorsal unpaired median (DUM) neurons revealed a dose-dependent hyperpolarization induced by DMDS associated with a decrease in the input resistance and the disappearance of action potentials. The hyperpolarization was inhibited by glibenclamide and tolbutamide, and was dependent on intracellular ATP concentration, demonstrating a neurotoxicity via the activation of KATP channels. Finally, the same effects observed with oligomycin, 2,4-dinitrophenol, and KCN together with the studies of DMDS toxicity on isolated mitochondria confirmed an unusual action occurring through an inhibition of the mitochondrial respiratory chain complex IV (cytochrome oxydase). This DMDS-induced inhibition of complex IV subsequently decreased the intracellular ATP concentration, which thereby activated neuronal KATP channels mediating membrane hyperpolarization and reduction of neuronal activity. (+info)
Early production and scavenging of hydrogen peroxide in the apoplast of sunflower plants exposed to ozone.
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The present work set out to define the processes involved in the early O3-induced H2O2 accumulation in sunflower plants exposed to a single pulse of 150 ppb of O3 for 4 h. Hydrogen peroxide accumulation only occurred in the apoplast and this temporally coincided with the fumigation period. The inhibitor experiments suggested that both the plasma membrane-bound NAD(P)H oxidase complex and cell-wall NAD(P)H PODs contributed to H2O2 generation. To investigate the mechanisms responsible for O3-induced H2O2 accumulation further, both production and scavenging of H2O2 were investigated in the extracellular matrix after subcellular fractionation. The results indicated that H2O2 accumulation is a complex and highly regulated event requiring the time-dependent stimulation and down-regulation of differently located enzymes, some of which are involved in H2O2 generation and degradation, not only during the fumigation period but also in the subsequent recovery period in non-polluted air. Owing to the possible interplay between H2O2 and ethylene, the time-course of ethylene emission was analysed too. Ethylene was rapidly emitted following O3 exposure, but it declined to control values as early as after 4 h of exposure. The early contemporaneous detection of increased ethylene and H2O2 levels after 30 min of exposure does not allow a clear temporal relationship between these two signalling molecules to be established. (+info)