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PubMed2005

Pesticide resistance via transposition-mediated adaptive gene truncation in Drosophila.

To study adaptation, it is essential to identify multiple adaptive mutations and to characterize their molecular, phenotypic, selective, and ecological consequences. Here we describe a genomic screen for adaptive insertions of transposable elements in Drosophila. Using a pilot application of this screen, we have identified an adaptive transposable element insertion, which truncates a gene and apparently generates a functional protein in the process. The insertion of this transposable element confers increased resistance to an organophosphate pesticide and has spread in D. melanogaster recently.

Adaptation, Physiological↗
PubMed1976

Cytological effects of an organic phosphate pesticide on human cells in vitro.

This investigation was undertaken to determine the radiomimetic effects in vitro of the insecticide guthion [azinophos-methyl; O, O-dimethyl S-(4-oxobenzotriazino-3-methyl) phosphorodithioate] on two human cell lines, diploid (WI-38) and heteroploid (HEp-2). In WI-38 cells, dosages of 120, 140 and 160 microng/ml of guthion were effective in inducing an average chromosome breakage of 0.042, 0.058 and 0.165 respectively per cell. In control cells, the mean number of breaks per cell was 0.011. Chromosome breakages were significantly higher in treated cells. Since guthion prevents cells from entering into mitosis during treatment, the number of mitiotic cells decreases rapidly following treatment with higher concentrations. Similar dosages in treated HEp-2 cells also induced a high incidence of chromosome aberrations, the most common being chromatid breaks and exchanges. Infrequently noted were mild failure of condensation, despiralization, secondary constrictions, gaps, dicentric chromosomes and pulverization. To date, this study reaffirms previous findings of the potentially hazardous, mutagenic effects of guthion.

Azinphosmethyl↗
PubMed1979

The effects of a pesticide program on microbial populations from apple leaf litter.

The leaf litter microbial community was quantitatively and qualitatively changed when a standard pesticide schedule that comprised an insecticide, a bactericide, and a fungicide was applied to McIntosh apple trees in the summer. Effects were observed for two winters by four indirect assays and three direct methods. Populations were altered qualitatively both years, but the most striking difference was the quantitative impact from year to year. Bacteria, filamentous fungi, and yeasts from treated leaves were reduced 10- to 10 000-fold between November 1976 and April 1977 and did not recover until snow cover had melted in March. Reductions in 1977-1978 were negligible. The marked seasonal difference is attributed to meteorological influences. Fluorescent pseudomonads were among the bacteria depressed by chemicals. Of the 49 genera of fungi and yeasts isolated, Coniothyrium sp., Penicillium spp., Arthrobotrys spp., and Nodulisporium sp. were appreciably reduced, whereas Typhula spp., Pleurophomella sp., Sporobolomyces spp., and Rhodotorula spp. were substantially enhanced by the spray program.

Azinphosmethyl↗
PubMed1984

Estimation of dermal exposure to pesticides and its use in risk assessment.

The potential risks to humans resulting from the usage of a pesticide must be carefully assessed before the product is registered. One of the components in the risk assessment is the determination of the amount of pesticide to which the applicator is exposed. Traditional methods estimated dermal exposure by measuring the amount of pesticide deposited on absorbent patches worn on the applicator's body. A more recent approach consists of measuring urinary metabolite levels. A review of data obtained in humans and in rats suggests that the urinary concentration of dimethyl thiophosphate is a good indicator of dermal exposure to azinphos-methyl.

Air Pollutants, Occupational↗
PubMed2003

Contamination of rural surface and ground water by endosulfan in farming areas of the Western Cape, South Africa.

BACKGROUND: In South Africa there is little data on environmental pollution of rural water sources by agrochemicals. METHODS: This study investigated pesticide contamination of ground and surface water in three intensive agricultural areas in the Western Cape: the Hex River Valley, Grabouw and Piketberg. Monitoring for endosulfan and chlorpyrifos at low levels was conducted as well as screening for other pesticides. RESULTS: The quantification limit for endosulfan was 0.1 microg/L. Endosulfan was found to be widespread in ground water, surface water and drinking water. The contamination was mostly at low levels, but regularly exceeded the European Drinking Water Standard of 0.1 microg/L. The two most contaminated sites were a sub-surface drain in the Hex River Valley and a dam in Grabouw, with 0.83 +/- 1.0 microg/L (n = 21) and 3.16 +/- 3.5 microg/L (n = 13) average endosulfan levels respectively. Other pesticides including chlorpyrifos, azinphos-methyl, fenarimol, iprodione, deltamethrin, penconazole and prothiofos were detected. Endosulfan was most frequently detected in Grabouw (69%) followed by Hex River (46%) and Piketberg (39%). Detections were more frequent in surface water (47%) than in groundwater (32%) and coincided with irrigation, and to a lesser extent, to spraying and trigger rains. Total dietary endosulfan intake calculated from levels found in drinking water did not exceed the Joint WHO/FAO Meeting on Pesticide Residues (JMPR) criteria. CONCLUSION: The study has shown the need for monitoring of pesticide contamination in surface and groundwater, and the development of drinking water quality standards for specific pesticides in South Africa.

Agriculture↗
PubMed2000

Rates of spontaneous reactivation and aging of acetylcholinesterase in human erythrocytes after inhibition by organophosphorus pesticides.

The in vitro rates of spontaneous reactivation and aging in human erythrocyte acetylcholinesterase were studied after inhibition by a dimethoxy (R1R2) and diethoxy substituted (R1R2) organophosphate pesticide (OP) of general structure R1R2P(O)X. These have been compared with data for human plasma cholinesterase previously reported using a similar methodology. A significantly slower rate of aging for erythrocyte acetylcholinesterase was found compared to plasma cholinesterase, whether inhibited by dimethoxy or diethoxy substituted OPs. For diethoxy OPs the rate of spontaneous reactivation of the inhibited plasma enzyme was significantly slower than for the inhibited red cell enzyme. This acetylcholinesterase, and previously published plasma cholinesterase, data suggest that in practise a blood sample taken 30-40 h after significant acute OP exposure will still show inhibition in either plasma or erythrocyte cholinesterase when analysed, but that any inhibited plasma enzyme is more likely to be in the aged form. In contrast a substantial proportion of the erythrocyte acetylcholinesterase is found unaged and therefore sensitive to reactivation by oximes. Samples from an occupational exposure where depressions in plasma or erythrocyte cholinesterase activity from baseline measurements were reactivated ex vivo using the oxime 2-PAM support this hypothesis. These data also confirm that the plasma enzyme is a more sensitive than erythrocyte acetylcholinesterase as an indicator of OP exposure and thus the potential value of ex vivo oxime reactivation of erythrocyte acetylcholinesterase in a blood sample to indicate subclinical OP exposure may be limited. However, this study is too small to draw conclusions on the sensitivity of ex vivo oxime reactivation of acetylcholinesterase as a novel biomarker of excessive OP absorption. Given that there is a better relationship between anticholinergic symptoms and red cell acetylcholinesterase inhibition, and that the slower resynthesis rate of any aged or inhibited red cell enzyme may be interpretatively useful when venepuncture is delayed, it is suggested that red cell acetylcholinesterase activity does have a place in monitoring potential OP exposure.

Acetylcholinesterase↗
PubMed2001

Work characteristics and pesticide exposures among migrant agricultural families: a community-based research approach.

There are few data on pesticide exposures of migrant Latino farmworker children, and access to this vulnerable population is often difficult. In this paper we describe a community-based approach to implement culturally appropriate research methods with a migrant Latino farmworker community in Oregon. Assessments were conducted in 96 farmworker homes and 24 grower homes in two agricultural communities in Oregon. Measurements included surveys of pesticide use and work protection practices and analyses of home-dust samples for pesticide residues of major organophosphates used in area crops. Results indicate that migrant farmworker housing is diverse, and the amounts and types of pesticide residues found in homes differ. Azinphos-methyl (AZM) was the pesticide residue found most often in both farmworker and grower homes. The median level of AZM in farmworker homes was 1.45 ppm compared to 1.64 ppm in the entry area of grower homes. The median level of AZM in the play areas of grower homes was 0.71 ppm. The levels of AZM in migrant farmworker homes were most associated with the distance from fields and the number of agricultural workers in the home. Although the levels of AZM in growers and farmworker homes were comparable in certain areas, potential for disproportionate exposures occur in areas of the homes where children are most likely to play. The relationship between home resident density, levels of pesticide residues, and play behaviors of children merit further attention.

Adult↗
PubMed1985

Mutagenic efficiency of organophosphorus insecticides used in combined treatments.

Male mice (Q strain) received two consecutive injections of organophosphorus insecticides: a phosphonate (trichlorfon) was combined to a thiophosphate (methylparathion) or a dithiophosphate (malathion or methylazinphos) in order to evaluate the interactions at the genetic and cytogenetic levels. No increase in chromosome damage was observed in bone marrow cells, spermatogonia, and primary spermatocytes. In a dominant lethal mutation assay, the frequency of postimplantation lethality was not significantly increased over the control level. The percentage of preimplantation losses was enhanced, probably due to a toxic effect on male germ cells.

Animals↗
PubMed2001

Combined effects of predatory fish and sublethal pesticide contamination on the behavior and mortality of mayfly nymphs.

We evaluated the potential interaction of pesticide effect and predatory fish on behavior and mortality of a stream mayfly. Experiments in laboratory stream microcosms compared the activity, drift, and mortality of Baetis mayfly nymphs in the absence of fish with that in the presence of Cape galaxias (Galaxias zebratus), both species inhabiting the same stream environments in the Western Cape of South Africa. These two predator treatments were combined with exposure either to no pesticide or to 0.2 microg/L of the organophosphate insecticide azinphos-methyl (AZP) or 0.2 microg/L of the pyrethroid insecticide fenvalerate (FV). Such pesticide levels are known from transient spraydrift- or runoff-related pesticide input into running waters. Each of the six combinations was replicated six times as 30-min trials during the day and effects were analyzed using 2 x 2 factorial analysis of variance (ANOVA). A single exposure to either fish or pesticide significantly increased the absolute activity of mayflies, measured as number of animals visible on top of stones, and the absolute mayfly drift in the fish treatment and in the FV treatment but did not increase the mortality above 0.8%. The combination of predator presence and sublethal pesticide exposure resulted in a significant increase in the mortality rate, to about 9% in the AZP x fish and 25% in the FV x fish treatment, although the activity and drift rates were not increased compared with the single-stressor treatments. Two-by-two factorial ANOVA and the comparison of expected and measured responses indicated that the mortality resulted from a synergistic interaction of the two stressors. The observed mortality was without exception caused by predation of the fish on drifting mayflies. The relative drift rate in the FV x fish treatment was decreased, again due to a synergistic interaction, which suggests an active drift avoidance reaction of the mayflies exposed to the combined pesticide x fish treatment, in contrast with those exposed just to FV. We conclude that the drift response of mayflies to transient sublethal pesticide exposure results in a synergistically increased adverse effect in the presence of predatory fish.

Animals↗
PubMedDate not supplied

Spray deposition of two insecticides into surface waters in a South African orchard area.

Drift from pesticide spray application can result in contamination of nontarget environments such as surface waters. Azinphos-methyl (AZI) and endosulfan (END) deposition in containers of water was studied in fruit orchards in the Western Cape, South Africa. Additionally, attention was given to the contamination in farm streams, as well as to the resulting contamination of the subsequent main channel (Lourens River) approx. 25 km downstream of the tributary stream inlets. Spray deposit decreased with increasing distance downwind and ranged from 4.7 mg m(-2) within the target area to 0.2 mg m(-2) at 15 m downwind (AZI). Measured in-stream concentrations of both pesticides compared well with theoretical values calculated from deposition data for the respective distances. Furthermore, they were in the range of values predicted by an exposure assessment based on 95th-percentile values for basic drift deposition (German Federal Biological Research Centre for Agriculture and Forestry [BBA] and USEPA). Pesticide deposition in the tributaries was followed by a measurable increase of contamination in the Lourens River. Mortality of midges (Chironomus spp.) exposed for 24 h to samples obtained from the AZI trials decreased with decreasing concentrations (estimated LC50 from field samples = 10 microg L(-1) AZI; lethal distance: LD50 = 13 m). Mortality in the tributary samples averaged 11% (0.5-1.7 microg L(-1) AZI), while no mortality was discernible in the Lourens River samples (0.041 microg L(-1)). The sublethal endpoint failure to form tubes from the glass beads provided was significantly increased at all sites in comparison with the control (analysis of variance [ANOVA], Fisher's protected least significant difference [PLSD], p < 0.01).

Agriculture↗
PubMedDate not supplied

Pesticide residues on fruits and vegetables from Ontario, Canada, 1991-1995.

For the 5-year period 1991 to 1995, 1536 vegetable and 802 fruit samples were analyzed. The purpose of this study was to determine if pesticides were present on Ontario-produced fruits and vegetables, and if so, to determine if residues violated maximum residue limits (MRLs). Overall, 31.5% of the samples had no detectable pesticide residues, whereas 68.5% contained one or more residues. Most of the residues were present at very low concentrations; 48% of the detections were < 0.1 parts per million (ppm), and 86% were < 1 ppm. However, violations of MRL were observed in only 3.2% of the vegetables samples and 3.1% of the fruit samples. In addition, 4.8% of the samples contained a "technical" violation, that is, there was no specified MRL for the pesticide-commodity combination and the residues exceeded 0.1 ppm. Of the detectable residues, 63% were < 10% of the MRL, whereas 89% were < 50% of the MRL. More fruit samples (91.4%) had a detectable residue, compared with vegetable samples (56.6%). Fruit is often treated close to harvest or post harvest to ensure that wholesome produce reaches the consumer. Forty-six percent of the samples contained 2 or more residues, and 2% of all samples had more than 5 different pesticides detected; fruit samples tended to have more multiple residues. The most frequently found pesticides were captan, the dithiocarbamate fungicides, endosulfan, azinphos-methyl, phosmet, parathion, and iprodione. These pesticides were also used in the greatest quantity for crop production. Overall, the data agree fairly closely with those reported for the U.S. Department of Agriculture Pesticide Data Program because the 2 programs have similar analytical goals and objectives.

Aminoimidazole Carboxamide↗