CiteULike: Tag pesticides

Repeatability and validity of a field kit for estimation of cholinesterase in whole blood.

L London — 2008-04-23T17:54:57-00:00

Occupational and environmental medicine, Vol. 52, No. 1. (January 1995), pp. 57-64.

OBJECTIVES--To evaluate a spectrophotometric field kit (Test-Mate-OP) for repeatability and validity in comparison with reference laboratory methods and to model its anticipated sensitivity and specificity based on these findings. METHODS--76 farm workers between the age of 20 and 55, of whom 30 were pesticide applicators exposed to a range of organophosphates in the preceding 10 days, had blood taken for plasma cholinesterase (PCE) and erythrocyte cholinesterase (ECE) measurement by field kit or laboratory methods. Paired blinded duplicate samples were taken from subgroups in the sample to assess repeatability of laboratory and field kit methods. Field kits were also used to test venous blood in one subgroup. The variance obtained for the field kit tests was then applied to two hypothetical scenarios that used published action guidelines to model the kit's sensitivity and specificity. RESULTS--Repeatability for PCE was much poorer and for ECE slightly poorer than that of laboratory measures. A substantial upward bias for field kit ECE relative to laboratory measurements was found. Sensitivity of the kit to a 40% drop in PCE was 67%, whereas that for ECE was 89%. Specificity of the kit with no change in mean of the population was 100% for ECE and 91% for PCE. CONCLUSION--Field kit ECE estimation seems to be sufficiently repeatable for surveillance activities, whereas PCE does not. Repeatability of both tests seems to be too low for use in epidemiological dose-response investigations. Further research is indicated to characterise the upward bias in ECE estimation on the kit.

Screening for insecticide overexposure under field conditions: a reevaluation of the tintometric cholinesterase kit.

R McConnell — 2008-04-22T17:12:33-00:00

American journal of public health, Vol. 84, No. 3. (March 1994), pp. 479-481.

A semiquantitative tintometric field kit has been used in the developing world for almost 30 years to measure whole blood cholinesterase levels in persons exposed to organophosphate pesticides. The validity of this screening kit was evaluated among 79 workers heavily exposed to organophosphates by comparison with a reference assay for erythrocyte cholinesterase. Overall correlation between the two methods was good. However, either sensitivity or specificity of the tintometric kit was less than 75% for each of the three tintometric categories commonly used to define the limit of normal. Because baseline erythrocyte cholinesterase levels were not available for this population, the true sensitivity and specificity of the tintometric assay may be even lower.

Pesticide exposures, cholinesterase depression, and symptoms among North Carolina migrant farmworkers.

S Ciesielski — 2008-04-22T17:10:35-00:00

American journal of public health, Vol. 84, No. 3. (March 1994), pp. 446-451.

OBJECTIVES. We conducted a clinic-based study of erythrocyte cholinesterase levels, pesticide exposures, and health effects among farmworkers and nonfarmworkers to determine risks for exposure and associated morbidity. METHODS. Two hundred two farmworkers and 42 nonfarmworkers were recruited sequentially at two community health centers. Erythrocyte cholinesterase levels were measured colorimetrically. Questionnaires obtained data on demographics, occupational history, exposures, and symptoms. RESULTS. Cholinesterase levels were significantly lower among farmworkers (30.28 U/g hemoglobin) than among nonfarmworkers (32.3 U/g hemoglobin). Twelve percent of farmworkers, but no nonfarmworkers, had very low levels. Farmworkers applying pesticides also had lower cholinesterase levels. One half of farmworkers reported being sprayed by pesticides and working in fields with an obvious chemical smell. Of reported symptoms, only diarrhea was associated with cholinesterase levels. Reported exposures, however, were strongly associated with symptoms. CONCLUSIONS. Farmworkers reported many pesticide exposures that violate state and federal regulations. Farmworkers had cholinesterase levels significantly lower than those of nonfarmworkers, although only spraying pesticides was associated with very low levels.

Cholinesterase measurements with an automated kit.

GH Oliveira — 2008-04-24T01:05:15-00:00

American journal of industrial medicine, Vol. Suppl 2 (August 2002), pp. 49-53.

BACKGROUND: The Test-mate kit determines acetylcholinesterase (AChE, EC 3.1.1.7) and hemoglobin content of a drop of blood, displaying enzyme activities normalized to 25 degrees C. Previous models produced inconsistent results at different temperatures. This report focuses on the current model, ChE 400, and two instruments of a previous OP model. METHODS: AChE activities were determined by the Ellman assay, using the three kits and a 96-well microplate reader. Temperatures ranged from 10 to 37 degrees C. Fetal bovine serum was the source of AChE. RESULTS: Normalized activities decreased below 20 degrees C in the ChE model and below 25 degrees C in the OP models. Activities of the same serum sample differed between the three Test-mate kits, ranging from 1.03 to 1.49 micromoles/min/ml. Percent errors were greater than with the microplate reader at all temperatures. CONCLUSIONS: Neither we nor the manufacturer recommend the current Test-mate model for fieldwork. Nevertheless, there have been field measurements with Test-Mate kits, and we recommend that an enzyme activity standard be run in parallel with their use.

Parkinson's disease and pesticides: a toxicological perspective

Jaime Hatcher — 2008-06-04T16:54:29-00:00

Trends in Pharmacological Sciences, Vol. 29, No. 6. (June 2008), pp. 322-329.

Environmental factors have been shown to contribute to the incidence of Parkinson's disease (PD). Pesticides, which represent one of the primary classes of environmental agents associated with PD, share the common feature of being intentionally released into the environment to control or eliminate pests. Pesticides consist of multiple classes and subclasses of insecticides, herbicides, rodenticides, fungicides, fumigants and others and exhibit a vast array of chemically diverse structures. In this review we examine the evidence regarding the ability of each of the major pesticide subclasses to increase the incidence of PD. We propose that, from a toxicological perspective, it would be beneficial to identify specific subclasses, common structural features and the propensity for widespread human exposure when considering the potential role in PD, rather than using the overly broad term of [`]pesticides' to describe this diverse group of chemicals. Furthermore, these chemicals and their environmentally relevant combinations should be evaluated for their ability to promote or accelerate PD and not merely for being singular causative agents.

Water Erosion Processes and the Enrichment of Sorbed Pesticides. Part 2. Enrichment Under Rainfall Dominated Erosion Process

H Ghadiri — 2008-01-04T18:30:50-00:00

Journal of Environmental Management, Vol. 37, No. 1. (January 1993), pp. 37-50.

Rainfall erosion experiments were carried out on a clay soil containing high concentrations of organochlorine pesticides aldrin and dieldrin. Soil placed in a 6 x 1 m flume was subjected to simulated rainfall of rate 100 mm/h and average raindrop diameter of 2[middle dot]2 mm. Samples of sediment transported out of the flume at various time intervals, and samples of soil left behind at the end of the erosion event were subjected to chemical extraction and their pesticide contents measured. Results show that the enrichment of both pesticides in the eroded sediment of all experiments was dependent upon the erosion duration and the size of the eroded particles. A major finding was that fine particles in the eroded sediment had a significantly higher pesticide content than particles of similar size in the original soil. The pesticide content of large aggregates was also reduced during erosion and sediment transportation. Such changes can be explained by raindrop stripping mechanism of large aggregates and the high pesticide concentration typical on the outer layers of stable aggregates. Pesticide concentration of the outer layer of aggregates can remain high compared to the inner part for several years after application, and, in the raindrop stripping process, these layers are broken down into fine particles rich in sorbed pesticides. Time dependency of the concentration ratio of sorbed pesticide shown in the results further supports the occurrence of this raindrop stripping process. The fine particles formed early in the erosion event are highly enriched but enrichment declines with time. The concentration ratio of different particle sizes of the eroded sediment tended, through time, to become similar to that of the soil left behind at the end of the erosion event.

Water Erosion Processes and the Enrichment of Sorbed Pesticides. Part 1. Enrichment Mechanisms and the Degradation of Applied Pesticides

H Ghadiri — 2008-01-04T18:29:20-00:00

Journal of Environmental Management, Vol. 37, No. 1. (January 1993), pp. 23-35.

Enrichment mechanisms and disappearing rates of organochlorine pesticides were studied using well-aggregated clay soils with a past history of pesticide applications. Heptachlor labelling experiments revealed that a concentration gradient within the soil aggregates is established upon the application of a pesticide, with the concentration in the surface layers being substantially higher than in the inner parts. Antecedent water content of treated aggregates did not change this feature, the concentration gradient being similar whether pesticide was applied to wet or dry aggregates. Removal of such a chemically rich outer layer of aggregates by rain erosion through the raindrop peeling mechanism resulted in the enrichment of pesticides in the eroded sediment, and this enrichment was specially pronounced for the first few erosion events after pesticide application. Such a peeling process results in an overall decline with time in the pesticide content of the soil. However, because the concentration gradient within the remaining parts of aggregates still prevails, the pesticide enrichment ratio of eroded sediment, though decreasing, continues to be higher than unity for several years after pesticide application to soil. Disappearing rates of dieldrin and aldrin from the soil were measured and found to follow a first-order rate equation. The equations fitted to the collected data predict longer persistence periods in the soil for both dieldrin and aldrin than previous estimates given in the literature. Results of aldrin and dieldrin analysis carried out on some other soils of the region are in agreement with the values obtained by using equations obtained in this study. The relative contribution of organic and non-organic constituents of soil to its sorbed pesticide content was measured. Organic matter adsorbed higher concentrations of aldrin and dieldrin than the non-organic fraction, but this fraction released its pesticide content at a faster rate than the non-organic fraction. Organic matter as a pool for sorbed pesticides in the soil is more important in the short term than in a longer duration after pesticide application. Organic matter shows a higher affinity to adsorb aldrin than dieldrin, thus affecting long-term degradation and persistence of these two pesticides.

The conundrum of unmeasured confounding: Comment on: "Can some of the detrimental neurodevelopmental effects attributed to lead be due to pesticides? by Brian Gulson"

Bruce Lanphear — 2008-03-15T21:24:10-00:00

Science of The Total Environment, Vol. In Press, Corrected Proof

The problem described by Dr. Brian Gulson - confounding by unmeasured exposures to pesticides - is only the most recent in a series of potential confounders cited to explain the observed effect of lead on children's intellectual abilities or behavioral problems. Despite the persistent problem of unmeasured confounders, there are several lines of evidence implicating lead as a toxicant at blood lead levels < 10 [mu]g/dL. First, in striking contrast with pesticides, there is considerable evidence from numerous studies linking low-level lead exposure with cognitive deficits and behavioral problems, even after controlling for a variety of potential confounders. Second, the consistency of evidence from diverse cohorts and distinct, if not always directly measured potential confounders -- enhances our confidence that the lead effect observed at blood lead levels < 10 [mu]g/dL is not attributable to unmeasured confounders. Third, in our reanalysis of the Rochester Lead Study, the inclusion of parent-reported mouthing behaviors and breastfeeding status did not attenuate the effect of lead exposure on children's intellectual function. Finally, although we can never entirely dismiss unmeasured confounding in observational studies, we can rely on experimental studies of lead-exposed animals to confirm that lead is a toxicant. Thus, while we must remain vigilant for unmeasured or poorly measured confounders, it is crucial to balance the endless search for confounders with the evidence of toxicity and the need to take action to protect public health. The alternative, to perpetually permit children to be exposed to lead and other emerging toxicants, is both absurd and unacceptable.

Incident diabetes and pesticide exposure among licensed pesticide applicators: Agricultural Health Study, 1993-2003.

MP Montgomery — 2008-07-14T12:14:56-00:00

American journal of epidemiology, Vol. 167, No. 10. (15 May 2008), pp. 1235-1246.

Exposure to certain environmental toxicants may be associated with increased risk of developing diabetes. The authors' aim was to investigate the relation between lifetime exposure to specific agricultural pesticides and diabetes incidence among pesticide applicators. The study included 33,457 licensed applicators, predominantly non-Hispanic White males, enrolled in the Agricultural Health Study. Incident diabetes was self-reported in a 5-year follow-up interview (1999-2003), giving 1,176 diabetics and 30,611 nondiabetics for analysis. Lifetime exposure to pesticides and covariate information were reported by participants at enrollment (1993-1997). Using logistic regression, the authors considered two primary measures of pesticide exposure: ever use and cumulative lifetime days of use. They found seven specific pesticides (aldrin, chlordane, heptachlor, dichlorvos, trichlorfon, alachlor, and cyanazine) for which the odds of diabetes incidence increased with both ever use and cumulative days of use. Applicators who had used the organochlorine insecticides aldrin, chlordane, and heptachlor more than 100 lifetime days had 51%, 63%, and 94% increased odds of diabetes, respectively. The observed association of organochlorine and organophosphate insecticides with diabetes is consistent with results from previous human and animal studies. Long-term exposure from handling certain pesticides, in particular, organochlorine and organophosphate insecticides, may be associated with increased risk of diabetes.

Organic diets significantly lower children's dietary exposure to organophosphorus pesticides.

C Lu — 2006-03-12T09:23:27-00:00

Environ Health Perspect, Vol. 114, No. 2. (February 2006), pp. 260-263.

We used a novel study design to measure dietary organophosphorus pesticide exposure in a group of 23 elementary school-age children through urinary biomonitoring. We substituted most of children's conventional diets with organic food items for 5 consecutive days and collected two spot daily urine samples, first-morning and before-bedtime voids, throughout the 15-day study period. We found that the median urinary concentrations of the specific metabolites for malathion and chlorpyrifos decreased to the nondetect levels immediately after the introduction of organic diets and remained nondetectable until the conventional diets were reintroduced. The median concentrations for other organophosphorus pesticide metabolites were also lower in the organic diet consumption days; however, the detection of those metabolites was not frequent enough to show any statistical significance. In conclusion, we were able to demonstrate that an organic diet provides a dramatic and immediate protective effect against exposures to organophosphorus pesticides that are commonly used in agricultural production. We also concluded that these children were most likely exposed to these organophosphorus pesticides exclusively through their diet. To our knowledge, this is the first study to employ a longitudinal design with a dietary intervention to assess children's exposure to pesticides. It provides new and persuasive evidence of the effectiveness of this intervention.

Organochlorine and organophosphorus pesticide residues in the Atoya river basin, Chinandega, Nicaragua

Castilho — 2008-02-26T15:11:26-00:00

Environmental Pollution, Vol. 110, No. 3. (December 2000), pp. 523-533.

The hydrographic basin of the Atoya river, located in the Department of Chinandega, one of the main cotton producing regions in Nicaragua, is intensively contaminated by pesticides. Samples of river waters and sediments, as well as strategically selected wells have been analyzed to study variations in the concentrations of organochlorine and organophosphorus pesticide residues between the dry season (November-April) and the rainy season (May-June). Generally, higher concentrations of pesticides have been detected in the river waters and sediments in the dry season. DDT, DDD, DDE compounds and toxaphene are the most frequent organochlorine residues found in the water and sediment samples, while endrin, aldrin, dieldrin and lindane are mainly found in the waters of rivers and wells. Organophosphorus compounds were rarely detected. However, residues of ethion, methyl-parathion and ethyl-parathion were found in high concentrations in some river and well water samples. Generally, organochlorine compounds tend to accumulate in the fine grain-size fractions, rich in organic matter, except DDE, which concentrates basically in the coarse grain-size fractions.

Biotic Indices and Stream Ecosystem Processes: Results from an Experimental Study

Bruce Wallace — 2007-03-06T15:06:30-00:00

Ecological Applications, Vol. 6, No. 1. (1996), pp. 140-151.

We investigated the ability of the North Carolina Biotic Index (NCBI) and the Ephemeroptera + Plecoptera + Trichoptera (EPT) index to track an experimental manipulation of the invertebrate community and resultant alteration of several ecosystem-level processes in a headwater stream at the Coweeta Hydrologic Laboratory in western North Carolina. Indices were calculated from quantitative monthly or bimonthly benthic samples of moss-covered rockface and mixed substrate habitats, as well as habitat-weighted values based on the proportion of each habitat in the two streams. One stream (C 55) served as a reference stream over the 6-yr period of late 1984 through 1990, whereas the other (C 54) received seasonal treatments with an insecticide for 3 yr (1986-1988). Throughout pretreatment, treatment, and recovery, both the NCBI and EPT indices tracked the disturbance regime of the treatment stream. Indices for the reference stream varied little during the 6-yr period. Both the NCBI and EPT suggested strong changes in the treatment stream during treatment relative to both pretreatment and the reference stream. Following cessation of insecticide treatments, both indices reflected improved biotic conditions during first and second years of recovery in C 54. Compared with fauna of mixed substrates, rockface fauna had lower (better) NCBI values during pretreatment, and exhibited a greater proportional increase in tolerant taxa during treatment than mixed substrates, emphasizing the importance of including rockface communities in environmental monitoring programs. Changes in both the EPT and NCBI indices closely corresponded to changes in ecosystem-level processes observed in C 54 from pretreatment to treatment, and recovery periods. These processes include: leaf litter processing rates, organic matter storage, fine particulate organic matter generation and export, and secondary production. With the exception of organic matter storage, all of these processes declined during treatment of C 54, and subsequently increased during recovery. Our results demonstrate the potential of such indices to detect and monitor stream ecosystem changes during and following disturbance. The EPT index was by far the easiest to use from both the standpoint of time required for sample processing and ease of application. Compared with the labor-intensive sample processing, specimen identification and measurement, and data entry required for secondary production calculations, the EPT index was relatively simple and displayed a remarkable ability to track secondary production of invertebrates in the treatment stream. Our data strongly support the inclusion of the EPT and NCBI indices in these southern Appalachian headwater streams as indicators of both degradation and recovery of stream ecosystem processes from chemical-induced disturbance.

Influence of Feeding Habits on Organochlorine Contaminant Accumulation in Waterfowl on the Great Lakes

Edward Mazak — 2007-02-13T14:56:36-00:00

Ecological Applications, Vol. 7, No. 4. (1997), pp. 1133-1143.

Zebra mussels (Dreissena polymorpha) are an important component of benthic communities in the Great Lakes and are exploited by a host of predators, including waterfowl. In this study, we analyze diet content and stable isotope and organochlorine contaminant patterns in Lesser Scaup (Aythya affinis), Greater Scaup (Aythya marila), Bufflehead (Bucephala albeola), Redhead (Aythya americana), Canvasback (Aythya valisineria), and Mallard (Anas platyrhynchos) collected from three sites (Fighting Island, western Lake Erie, Big Creek) in the lower Great Lakes. Lesser and Greater Scaup from Fighting Island were classified as either zebra mussel (67% of diet) or macrophyte (85% of diet) consumers. Bufflehead, Canvasback, Mallard, and Redhead consumed mainly (89%) macrophyte at Fighting Island. Zebra mussel was the principal food of Lesser Scaup (>99%), Greater Scaup (97%), and Bufflehead (72%) in western Lake Erie. Stable isotope analysis revealed enrichment of δ15N in Lesser Scaup (2.24‰), Greater Scaup (1.28‰), and Bufflehead (0.63‰) that exploited mussels relative to conspecifics with macrophyte diets and relative to mussel prey. Representative contaminants of low (hexachlorobenzene [HCB]), moderate (PCB [polychlorinated biphenyl] 153), and high (PCB 180) hydrophobicity were examined in waterfowl. Lipid-normalized concentrations of PCBs 153 and 180 were significantly higher in scaup and Bufflehead that consumed Dreissena than in individuals that ate mainly macrophytes. Among taxa that consumed primarily Dreissena concentrations of PCBs 153 and 180 were significantly higher in individuals from Lake Erie than in those Fighting Island. Principal components analysis revealed broad differences in contaminant patterns of waterfowl based principally on diet. Results from this study illustrate that Dreissena has become a primary food source of some waterfowl in the lower Great Lakes and serves as an effective conduit for transfer of persistent organic contaminants to higher trophic levels.

Can fungal biopesticides control malaria?

Matthew Thomas — 2007-04-17T10:39:09-00:00

Nature Reviews Microbiology, Vol. 5, No. 5. (11 April 2007), pp. 377-383.