Terry L. Lavy

Measurements of year-long exposure to tree nursery workers using multiple pesticides.

A year-long nurseryworker pesticide exposure study was designed to measure and evaluate the exposure occurring to workers who had the potential for simultaneous exposure to multiple pesticides. This four-State study was conducted in five nurseries (four USDA Forest Service and one State) involved in conifer seedling production. Primary comparisons were made among nursery workers in the Pacific northwest and south central United States. Worker exposure was assessed by using patches attached to clothing, handrinse samples and urine excreted from potentially exposed workers. In addition, dislodgeable residue in rinsate from a water wash of pesticide-treated seedlings was also evaluated. Four different groups of field workers, designated as applicators, weeders, scouts and packers, were included. The pesticide absorbed dose, assessed by urine analysis of pesticide metabolites and the deposition of pesticide on patches attached to the clothing of field workers, was monitored as they performed their duties under normal conditions (e.g., typical clothing, pesticide application). Monitoring was performed for the 14 different pesticides which were used in these nurseries. Seven pesticides were studied in more detail using biological monitoring. For these compounds, metabolites known to be excreted in the urine of exposed humans or other mammals were used to estimate the dose of pesticide absorbed by the exposed workers.The highest percentage of positive samples came from dislodgeable residue samples (8.3%) followed by patch samples (3.2%), handrinse (2.9%), and urine samples (1.3%). To summarize the conclusions from the urinary excretion data, 12 of the 73 nursery workers in the study received a low absorbed dose of pesticide. Biological monitoring revealed that three pesticides (benomyl, bifenox and carbaryl) were found in the urine of some of the workers. Of the 3,134 urine samples analyzed there were 42 positive; 11 urine samples were positive for benomyl, while bifenox was responsible for 13 positives and carbaryl accounted for the remaining 18. The 12-week continuous monitoring of urine showed that metabolites of these materials were rapidly excreted; thus, no build-up in the body is anticipated. Margins of Safety (MOS) calculations were made to provide an assessment of the significance of the exposure. Based on the low frequency of positive urine samples in the study, the low levels of metabolites when they were found, their apparent rapid excretion rate and the No Observed Effect Level (NOEL) data, furnished from other sources, nursery worker exposure to pesticides in these conifer nurseries is below health threatening levels.

Influence of Dissolved Humic Acid and Ca-Montmorillonite Clay on Pesticide Extraction Efficiency from Water Using Solid-Phase Extraction Disks

Intermittent rain can influence the sediment load in surface runofffrom agricultural fields, thereby causing variability in amounts of sediment and dissolved organic matter (DOM) in the water that could adversely affect extraction efficiency and ultimately the method sensitivity of pesticide analyses in water monitoring studies. Therefore, a study was conducted to determine the effect of purified sediment components, Ca-montmorillinite clay and commercial humic acid, on extraction efficiency of 12 pesticides from water using solid-phase extraction (SPE) disks. Batches of water at pH 6.0 and 8.0 were prepared at an ionic strength of 3 x 10 -3 M. Individual water samples (250 mL) at each pH containing 20 μg L -1 each pesticide were amended with all possible combinations of (a) commercial humic acid at either 0, 5, 10, or 25 mg L -1 dissolved organic carbon (DOC) and (b) Ca-montmorillinite amounts of either 0, 0.01, 0.1, or 1 g. Samples were prefiltered to remove clay and then extracted using solid-phase extraction (SPE) disks. Pesticides eluted from disks were analyzed by gas chromatography/mass spectroscopy (GC/MS). Pesticides within chemical families reacted similarly to treatments of pH, Ca-montmorillinite, and humic acid. The effects of Ca-montmorillinite and humic acid were generally pH-dependent and acted independently in affecting extraction efficiency. Lower recovery of most pesticides was observed at pH 8 when Ca-montmorillinite was ≥0.1 g and was attributed to greater dispersion of clay, increased surface area, and subsequent adsorption. Concentrations of DOC in humic acid had less effect on extraction efficiency when water was at pH 8 compared to water at pH 6, which was probably due to greater nonpolar interactions of pesticides to the charge-neutralized humic acid polymer.

The federal government's Agricultural Health Study: a critical review with suggested improvements.

The Agricultural Health Study (AHS) has approximately 90,000 pesticide applicators and their spouses enrolled in a number of studies to determine whether exposures to specific pesticides are associated with various cancers and other adverse health outcomes. Although the AHS was intended to be an integrated program of studies, some significant difficulties have emerged. In this report, we examine the design of the AHS, identify important program strengths and flaws, suggest various improvements in the program, and recommend ancillary studies that could be undertaken to strengthen the AHS. Overall, the AHS is collecting a large amount of information on potential determinants of health status among farmers and farm families. A promising feature of the AHS is the prospective cohort study of cancers among farmers in which the research design determines exposures prior to the diagnosis of disease. More effort needs to be devoted to reducing selection bias and information bias. Success of the cohort study will depend in part on follow-up surveys of the cohort to determine how exposures and disease states change as the cohort ages. The cross-sectional and case-control studies planned in the AHS are less promising because they will be subject to some of the same criticisms, such as potentially biased and imprecise exposure assessment, that have characterized the existing literature in this field. Important limitations of the AHS include low and variable rates of subject response to administered surveys, concerns about the validity of some self-reported non-cancer health outcomes, limited understanding of the reliability and validity of self-reporting of chemical use, an insufficient program of biological monitoring to validate the exposure surrogates employed in the AHS questionnaires, possible confounding by unmeasured, nonchemical risk factors for disease, and the absence of detailed plans for data analysis and interpretation that include explicit, a priori hypotheses. Although the AHS is already well underway, most of these limitations can be addressed by the investigators if adequate resources are made available. If these limitations are not addressed, the large amounts of data generated in the AHS will be difficult to interpret. If the exposure and health data can be validated, the scientific value of the AHS should be substantial and enduring. A variety of research recommendations are made to strengthen the AHS. They include reliability and validity studies of farmer reporting of chemical use, biological monitoring studies of farmers and members of farm families, and validity studies of positive and negative self-reports of disease status. Both industry and government should consider expanded research programs to strengthen the AHS.

Gas chromatographic determination of picloram in human urine

Picloram (4-amino-3,5,6-trichloropicolinic acid) is used to control broadleaf weeds and woody plants. It is used in forestry for site preparation and to help release pine seedlings from broadleaf competition. The use of any pesticide requires that we monitor not only its effectiveness but also the exposure of human beings to the compound. Methods for analyses of exposure and the fate of compounds differ for individual pesticides. Although methods have been developed for analysis of picloram from urine, none have been reported using boron trifluoride methylation with C18 cartridge cleanup and electron capture detection. Nolan et al. (1984) have reported that 88-94% of picloram that had been orally ingested by human volunteers was excreted unchanged in the urine within 72 hours. In the same paper they report an analytical method for picloram in urine using GC/MS with a limit of quantification of 10 ppb. Tonder and Daugherty (1981) have reported an analytical screening method for acidic toxic substances involving diazo-methane derivatization followed by florisil cleanup. The percent recovery for picloram was 60-63% at 40 ppb. Draper (1982) also used diazomethane derivatization with a recovery of 104 ~ 6% for 4 replications fortified at 100 ppb. Libich et al. (1984) analyzed for picloram with a Hall detector in the chlorine mode following base hydrolysis and methylation with boron trifluoride in methanol. The mean recovery was 80% with a range of 76% to 90%. In order to complete one of our research projects, we needed an analytical method for picloram in urine using election capture detection. We also wished to avoid the use of diazomethane due to the potential health hazards associated with it. Our method affords a limit of quantification of 10 ppb.