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PubMed2002

Fate and bioaccumulation of isoproturon in outdoor aquatic microcosms.

To gain information concerning the ecotoxicity of isoproturon (IPU) on aquatic ecosystems, six experimental ponds of 5 m3 each were studied. All the experiments were conducted during the summer over two years. Three different types of ecosystems were tested in 1994 and one type of ecosystem was selected and repeated in 1995 with three replicates. In each case, the initial concentration of IPU contamination was set at 10 microg/L. The IPU concentration was determined in the water column and in different species (mainly plants) of the microcosms. A first-order kinetic decrease in IPU concentration was observed in 1994, with half-life ranging from 15 to 35 d, depending on the microcosms. This relatively fast decrease was also confirmed in 1995, but it reached a constant value after two months. A high variability of the IPU concentration was observed in exposed plants, with bioconcentration factors ranging from 100 to 1,200 with large coefficients of variation. The observed plant bioconcentration factors are higher than those predicted by usual numerical models, probably due to the specific binding of IPU on one protein of the photosynthetic apparatus. Our data show that bioconcentration does not occur in mollusks but is important in photosynthetic organisms. Plant bioconcentration and microbial biodegradation are the main processes involved in the IPU decay in our outdoor aquatic microcosms.

Animals↗
PubMed2001

Biorational agents--mechanism and importance in IPM and IRM programs for controlling agricultural pests.

Among the new approaches for controlling agricultural pests is the development of novel compounds affecting specific processes in insects such as chitin synthesis inhibitors, juvenile hormone mimics and ecdysone agonists. In addition, efforts have been made to develop compounds acting selectively on groups of insects by inhibiting or enhancing biochemical sites such as respiration (diafenthiuron), the nicotinyl acetylcholine receptors (imidacloprid and acetamiprid), the GABA receptors (avermectins), the salivary glands of sucking pests (pymetrozine) and others. Among the most recent novel insecticides with selective properties are novaluron, thiamethoxam, emamectin and spinosad. Novaluron (Rimon) is a novel chitin synthesis inhibitor that acts by both ingestion and contact. It is a powerful suppressor of lepidopteran larvae such as Spodoptera littoralis and Helicoverpa armigera (by ingestion) and of whiteflies such as Bemisia tabaci and Trialeurodes vaporariorum (by contact). Thiamethoxam (Actarn), a novel neonicotinoid acts specifically on aphids and whiteflies. Emamectin (Proclaim), an avermectin derivative acts on GABA receptor affecting diversity of insects such as mites, lepidopterans and thrips. Spinosad (Tracer) seems to act on both acetylcholine and GABA receptors affecting diversity of insect species and is considered an important agent for controlling the western flower thrips.

Animals↗
PubMed2003

Metallothionein induction in the aquatic oligochaete Tubifex tubifex exposed to the herbicide isoproturon.

Metallothioneins (MTs), are low molecular weight proteins, mainly involved in metal ion detoxification. Recently it has been demonstrated that MTs participate in several cellular functions such as regulation of growth, and anti-oxidative defenses. Moreover, pesticides can induce their synthesis. The aim of the current work was to determine the effects of isoproturon either pure or formulated as Matin (suspension containing 500 g x l(-1) isoproturon) on the metallothionein and total protein content of the aquatic worm Tubifex tubifex. MT levels in exposed worms increased significantly after 7 and 15 days of exposure to 50 mg x l(-1) of herbicide. Isoproturon reduced metal (Cu, Zn, and Cd) content of metallothioneins, and it also increased total protein content of the worms. The results suggest that MT induction may not be considered as a specific biomarker of metal exposure but it can be used as a non specific biomarker of isoproturon effect in the worm.

Animals↗
PubMed1978

Anthelmintic control of concurrent Hymenolepis nana and Syphacia obvelata infections in the mouse with uredofos.

Tests were made to determine the efficacy of uredofos in either the diet or drinking water for controlling induced Hymenolepis nana and naturally acquired Syphacia obvelata infections in the mouse. Four levels of administration (50, 75, 100, and 125 parts per million) were used in a 6-day drugdiet assay. Consistent removal of Hymenolepis nana occurred only at 125 parts per million, whereas removal Syphacia obvelata was complete at all levels. The disodium salt of uredofos was given in the drinking water. Three levels of administration (12, 18 and 25 mg/kg) were used, and the treatment period was limited to 24 hours. Complete removal of Hymenolepis nana occurred at 25 mg/kg and Syphacia obvelata was completely eliminated at all levels.

Administration, Oral↗
PubMed1993

Haemotoxic effect of phenylurea herbicides in rats: role of haemoglobin-adduct formation in splenic toxicity.

Three substituted phenylurea herbicides were used for the study of the haemotoxic effects on rats of chronic exposure to these compounds. Female Sprague-Dawley rats were given monuron, diuron or fenuron (250-1000 mg/kg diet) for 14 months. The final body weights were similar to those of controls. No treatment-related effects on organ weights were observed at autopsy, except for a dose-related increase in spleen weights in rats treated with monuron or diuron, but not in those treated with fenuron. The proportion of haemoglobin in the form of methaemoglobin increased in the dosed group and resulted in a secondary anaemia with changes in the morphology of erythrocytes. Haemoglobin adducts of aromatic amines released from the herbicides were present at dose-related levels in rats treated with monuron or diuron. Compound-related lesions were observed histologically in treated rats, with increased pigmentation (haemosiderin) in the spleen, reflecting the response to the haemolytic anaemia and methaemoglobinaemia induced by the herbicides. Pigment deposition consisting of golden brown granules in the cytoplasm of the tubular epithelium in the kidney and in the Kupffer cells in the liver were observed only in rats treated with monuron. The haemotoxic effects that were observed may indicate that the formation of adducts between haemoglobin and the parent aromatic amines released metabolically from these herbicides has a role in the splenic toxicity of these compounds.

Animals↗
PubMed1999

Electrically driven microseparation methods for pesticides and metabolites. II: on-line and off-line preconcentration of urea herbicides in capillary electrochromatography.

Capillary electrochromatography (CEC) was introduced to the separation of nine important urea herbicides using octadecyl-silica (ODS) capillary columns that were specially designed to allow the realization of a relatively strong electroosmotic flow (EOF) and, in turn, fast separations. The ODS stationary phase was intentionally prepared to have a low surface coverage in octadecyl ligands in order to ensure a strong EOF. This ODS stationary phase of low surface coverage exhibited the usual reversed-phase chromatographic behavior as was manifested by the linearity of plots of log kappa versus the percent organic modifier in the mobile phase. The nature of the organic modifier of the mobile phase influenced the order of elution as well as the separation efficiency of the nine urea herbicides. Mobile phases containing acetonitrile yielded higher separation efficiency (by a factor of 1.5) than methanol-containing mobile phases. This was attributed to the higher mass transfer resistances of the solute in and out of the pores in the presence of the more viscous methanol-containing mobile phases. Due to the relatively strong affinity of the urea herbicides to the ODS stationary phase, on-line preconcentration consisting of prolonged injections allowed the determination of 10(-5) M urea herbicide samples using a UV detector without sacrificing separation efficiency. This was further decreased to 10(-7) M when the prolonged injection was preceded by the injection of a plug of water. The plug of water (the more retentive mobile phase) brought about an enhanced accumulation of the dilute samples into a narrow band at the inlet of the CEC column. When this on-column sample enrichment approach was combined with an off-line sample preconcentration step, which consisted of a solid-phase extraction process, ultra dilute samples of 10(-10) M (0.1 ppb) could be detected.

Chromatography, High Pressure Liquid↗
PubMedDate not supplied

Subchronic oral toxicity of a combination of insecticide (HCH) and herbicide (ISP) in male rats.

Rats were treated orally with technical hexachlorocyclohexane (HCH, 12.5, 25 and 50 mg kg-1 day(-1)) and technical isoproturon (ISP 22.5. 45 and 90 mg kg-1 day(-1)) daily for a period of 90 days alone and in combination. Treatment with HCH alone showed mild to severe toxicity and death. Significant changes occurred in liver weight, clinical enzyme profiles, haematological parameters and pathomorphological changes. Treatment with ISP alone did not produce such changes. The combination of HCH and ISP produced changes not suggestive of synergism.

Administration, Oral↗
PubMed2003

The influence of lipophilicity and formulation on the distribution of pesticides in laboratory-scale sediment/water systems.

Pesticide reaching surface waters will be sorbed by sediment. This sorption process and the influence of pesticide formulation have been examined at 10 degrees C in small-scale systems having 2-cm depth of sediment and 8-cm overlying water stirred gently. Eight pesticides (triasulfuron, isoproturon, chlorotoluron, phenmedipham, difenoconazole, chlorpyrifos, pendimethalin and permethrin), spanning a range of physicochemical properties, were applied individually to the water. Sorption equilibrium was reached at between 15 and 30 days, the proportion of pesticide then in the sediment ranging from 20% for the acidic and therefore polar triasulfuron to 97% for the lipophilic permethrin; this behaviour was not influenced by formulation. Sorption coefficients measured in batch tests over 2 h gave good estimates of the equilibrium distribution. Some degradation was observed for all compounds over 90 days; for some compounds and formulations, enhanced degradation occurred after 20 to 60 days. It is concluded that lipophilicity is the chief determinant of pesticide distribution in sediment/water systems.

Algorithms↗
PubMed2003

Variation of pesticide sorption isotherm in soil at the catchment scale.

The variation of the sorption isotherm of pesticides has seldom been explored at the catchment scale. Such a study was conducted at the scale of a 187-ha agricultural catchment for three herbicides: atrazine, isoproturon and metamitron. Partition coefficient (Kd) values were measured in batch experiments on 51 topsoil samples, and showed moderate variability at the catchment scale (coefficient of variation CV approximately 30%). Values of Kd ranged from 0.47 to 1.70 litre kg(-1) for atrazine, 0.47 to 1.81 for isoproturon, and 0.55 to 2.21 for metamitron. A clustering method was used to reduce the number of samples on which to measure sorption isotherms to 14. Sorption isotherms agreed with the Freundlich rather than the linear model. Kf parameters had CV values similar to those for Kd, with values ranging from 0.78 to 2.13 mg(1 - Nf) litre(Nf) kg(-1) for atrazine, 0.61 to 1.82 for isoproturon, and 0.69 and 2.58 for metamitron. Nf exponents showed little variation (CV < 5%). Nf values were between 0.86 and 0.98 for atrazine, 0.85 and 0.90 for isoproturon, and 0.82 and 0.87 for metamitron. More than 97% of the Kf catchment-scale variations could be explained by the variations of the soil organic carbon content.

Agriculture↗
PubMed2003

Capacity of model biobeds to retain and degrade mecoprop and isoproturon.

Biobeds are used to increase the adsorption and degradation of pesticide spillage on sites used for mixing and loading and for cleaning of sprayers. The adsorption and the rate of degradation of 14C-labelled isoproturon and mecoprop (MCPP) at concentrations from 0.0005 to 25 000 mgkg(-1) were determined in biobed soil. Further leaching of the two herbicides was determined in a model biobed with a surface area of 2 m2. The biobed material showed enhanced ability to adsorb the two herbicides. Kd was 5.2 litre kg(-1) for isoproturon and 1.6 litre kg(-1) for MCPP in biobed material, which is higher than in natural soil. In different experiments with natural soil, Kd ranges from 0.07 to 0.6 litrekg(-1) for MCPP and from 1.5 to 4.6 litre kg(-1) for isoproturon in soils with varying organic carbon content. Degradation of MCPP was rapid at concentrations from 0.0005 to 500 mg kg(-1), delayed at 5000 mg kg(-1), and very slow at 25 000 mg kg(-1). For isoproturon, the relative degradation was most rapid at the lowest concentration and decreasing with increasing concentrations. After 120 days, between 55% and 8% 14C was evolved as 14CO2 at concentrations between 0.0005 and 25 000 mg kg(-1). The rate of evolution of 14CO2 indicated that degradation rates at low concentrations were of first-order and at higher concentrations of zero-order. Leaching of MCPP and isoproturon was determined in a newly established model biobed during a 2-year period. About 13% of applied MCPP and 1.4% of applied isoproturon leached out during the winter following the first autumn application (worst-case scenario). Leaching was completely prevented when the biobed had a well-developed grass cover and was covered during the winter.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed2003

The ability of indigenous micro-organisms to degrade isoproturon, atrazine and mecoprop within aerobic UK aquifer systems.

The potential for the herbicides isoproturon, atrazine and mecoprop to degrade in the major UK aquifers of chalk, sandstone and limestone was studied using laboratory microcosms spiked at 100 microg litre(-1). Significant mecoprop degradation was only observed in sandstone groundwater samples. Atrazine transformation, based on the formation of metabolites, did occur in most groundwater samples, but only at a rate of 1-3% per year. A potential to degrade isoproturon was observed in groundwater samples from each of the aquifer types, with the most rapid and consistent degradation occurring at the sandstone field site. Biodegradation was confirmed by the formation of monodesmethyl- and didesmethyl-isoproturon. Isoproturon degradation potential rates obtained from the groundwater microcosms could not be correlated with either dissolved organic carbon or numbers of bacteria in the groundwater. It was noted that the ability of the groundwater at a field site to degrade a pesticide was not related to performance of the soil above.

2-Methyl-4-chlorophenoxyacetic Acid↗
PubMed1996

Availability and persistence of isoproturon under field and laboratory conditions.

Field and laboratory tests were conducted to investigate the disappearance and decrease in availability of the herbicide isoproturon in soil with time. Monitoring the fate of 14C-labeled isoproturon gave the persistence of the herbicide under different conditions. The calculated half-life (DT50) of the extractable parent product was close to 19 days for the two experiments, whereas half-lives of exhaustive extractable 14C-residues averaged 22 days under controlled conditions versus 48 days in the field. Moreover, if nonextractable 14C-residues were taken into account in estimating isoproturon fate, the DT50 of radioactive residues in soil (extractable parent and degradation products + nonextractable residues) reached 1 to 1.4 years under field and controlled conditions, respectively. The variability of disappearance rates for the different kinds of residues is discussed within a wider definition of persistence.

Biodegradation, Environmental↗
PubMed1999

Soil thin-layer chromatography and pesticide mobility through soil microstructures. New technical approach.

Soil thin-layer chromatography with water or water-methanol as solvents allows observation and measurement of the mobility of labelled pesticides through soil microstructures. Eleven different sieved matrices were studied: pure humine, pure clays, schists and soils. Ionized compounds (paraquat, glyphosate) were tightly bound to these matrices. The other compounds, lipophilic and generally non-ionized ones, migrated in the same order on most of the studied matrices, either mineral or organic: R(F) atrazine=isoproturon>diuron=fipronil>phenmedipham. This order was roughly correlated to log P but much more complex correlations were suggested. The rate of water movement, VWR, widely changed from one matrix to another. Therefore, the pesticide movement, M, in soil microstructures under the action of rain may be described by the equation M = WR R(F).

Atrazine↗
PubMed1999

A model for the formation and degradation of bound residues of the herbicide 14C-isoproturon in soil.

The humic monomer catechol was reacted with 14C-isoproturon and some of its metabolites, including 14C-4-isopropylaniline, in aqueous solution under a stream of oxygen. Only in the case of 14C-4-isopropylaniline, incorporation in oligomers, in fulvic acid-like polymers, and in humic acid-like polymers was observed. The main oligomer was identified by mass spectrometry as 4,5-bis-(4-isopropylphenylamino)-3,5-cyclohexadiene-1,2-dione. Oligomers and polymers containing bound 14C-4-isopropylaniline were subjected to biodegradation studies in a loamy agricultural soil during 55 days by quantifying 14CO2 evolved. In all cases, significant mineralization rates could be determined, which, however, were much smaller than those of free 14C-4-isoproturon and free 14C-4-isopropylaniline in the same soil.

Biodegradation, Environmental↗