Human Oral Buccal Microbiomes Are Associated with Farmworker Status and Azinphos-Methyl Agricultural Pesticide Exposure.

In a longitudinal agricultural community cohort sampling of 65 adult farmworkers and 52 adult nonfarmworkers, we investigated agricultural pesticide exposure-associated changes in the oral buccal microbiota. We found a seasonally persistent association between the detected blood concentration of the insecticide azinphos-methyl and the taxonomic composition of the buccal swab oral microbiome. Blood and buccal samples were collected concurrently from individual subjects in two seasons, spring/summer 2005 and winter 2006. Mass spectrometry quantified blood concentrations of the organophosphate insecticide azinphos-methyl. Buccal oral microbiome samples were 16S rRNA gene DNA sequenced, assigned to the bacterial taxonomy, and analyzed after "centered-log-ratio" transformation to handle the compositional nature of the proportional abundances of bacteria per sample. Nonparametric analysis of the transformed microbiome data for individuals with and without azinphos-methyl blood detection showed significant perturbations in seven common bacterial taxa (>0.5% of sample mean read depth), including significant reductions in members of the common oral bacterial genus Streptococcus Diversity in centered-log-ratio composition between individuals' microbiomes was also investigated using principal-component analysis (PCA) to reveal two primary PCA clusters of microbiome types. The spring/summer "exposed" microbiome cluster with significantly less bacterial diversity was enriched for farmworkers and contained 27 of the 30 individuals who also had azinphos-methyl agricultural pesticide exposure detected in the blood. IMPORTANCE: In this study, we show in human subjects that organophosphate pesticide exposure is associated with large-scale significant alterations of the oral buccal microbiota composition, with extinctions of whole taxa suggested in some individuals. The persistence of this association from the spring/summer to the winter also suggests that long-lasting effects on the commensal microbiota have occurred. The important health-related outcomes of these agricultural community individuals' pesticide-associated microbiome perturbations are not understood at this time. Future investigations should index medical and dental records for common and chronic diseases that may be interactively caused by this association between pesticide exposure and microbiome alteration.

The effect of the 14-day agricultural restricted entry interval on azinphosmethyl exposures in a group of apple thinners in Washington state.

We examined the effect of the 14-day agricultural restricted entry period on absorbed pesticide doses in a group of twenty experienced apple thinners. Thinners entered orchards 1-49 days following azinphosmethyl applications. Urine samples (n=296) collected throughout the thinning season were analyzed for the three dialkylphosphate metabolites of azinphosmethyl to estimate absorbed daily doses. Separate dose distributions were created for samples collected when the interval was <14 days, or 14 days or more; geometric mean doses for these two categories differed by a factor of two (42 and 19 microg/kg/day, respectively; p<0.0001). Dose estimates were compared to US Environmental Protection Agency and California EPA regulatory guidance values for occupational azinphosmethyl risk. None of the doses exceeded the U.S. EPA NOAEL (560 microg/kg/day), but nearly all had a margin of exposure of less than 100. Addition of a 10-fold uncertainty factor to California EPAs NOAEL produced a guidance value of 75 microg/kg/day. Only 2.4% of the doses exceeded this value for re-entry intervals 14 days or more, while 27% exceeded the value for re-entry intervals <14 days. We conclude that the 14-day restricted entry interval provides an appropriate level of worker health protection under the field conditions studied.

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).

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.

Comparison of three methods for assessment of hand exposure to azinphos-methyl (Guthion) during apple thinning.

Hand exposures of apple thinners to the pesticide azinphos-methyl (Guthion) were measured using three methods (glove, handwash, and wipe). Hand exposure sampling for each method was conducted following apple thinning work for a period of two hours for six to eight workers. Foliar residue samples were collected on each day of hand exposure sampling in the same orchard blocks that were thinned; foliar residues are considered to have been constant during the four-day study, which took place, on average, six days after pesticide application. Hand exposure estimates derived from each of the three methods differed significantly (ANOVA: p < 0.001). Mean measured exposure rates for the glove, handwash, and wipe methods were 6.48, 1.83, and 0.28 mg/hr, respectively. A corrected estimate of hand exposure, 2.7 mg/hr, was calculated from the handwash measurements and the handwash removal efficiency factor from a laboratory study. Comparison with this hand exposure estimate suggests that the glove method produced a 2.4-fold overestimate of exposure, whereas the wipe method produced a 10-fold underestimate. Studies that measure hand exposure to pesticides should include a careful description of sampling methods and should recognize the potential for measurement bias. Furthermore, the standardization and validation of dermal exposure assessment methods are critical to developing more comparable and more accurate pesticide exposure estimates.

Farmworker exposure to organophosphorus pesticide residues during apple thinning in central Washington State.

The purpose of this study was to characterize worker exposure to azinphos-methyl (Guthion) over an entire 4-6 week apple-thinning season. Twenty workers from three work sites in the Chelan-Douglas County region of Washington state were recruited for the study. Exposure potential was estimated by dislodgeable foliar residue measurements, and individual exposures were estimated by biological monitoring through urinary metabolites. Measureable azinphos-methyl residues were found on apple foliage at all sites throughout the six-week sampling period, indicating continuous exposure potential (median residue level of 0.5 microgram/cm2). Measurable levels of the urinary dialkylphosphate metabolite, DMTP, were found in virtually all urine samples (limit of detection = 0.04 microgram/mL). Mean DMTP concentrations differed significantly across sites (0.53, 0.29, and 0.90 microgram/mL for Sites 1-3, respectively; analysis of variance, p < .002), and intraindividual variability was much greater than interindividual differences. Group mean DMTP concentrations at each site fluctuated according to foliar residue levels. Measurable DMTP concentrations were found in 9% of reference workers, ranging from 0.04-0.18 microgram/mL. Cholinesterase activity levels monitored with a field test kit were not considered reliable due to temperature changes of the instrument.