Regulating OP pesticide residues for farmworker protection

Degradation of phosalone by silver ion catalytic hydrolysis

Pesticides application is expanding globally as the worldwide population increases demanding a secure and safe food supply. Organophosphorus (OP) pesticides, as a group, are widely used because they are rapidly degraded in the environment and because they have excellent efficacy and an acceptable price point. However, the chemical fate of organophosphorus pesticides is influenced by several factors, including their chemistry in aquatic environments. Among many degradation choices, hydrolysis by metal ions appears to be a good approach. Dissolved metal ions have been shown to promote the hydrolysis of organophosphorus pesticides. Using silver ion, we showed the effectiveness under in vitro and in vivo conditions for this metal ion to decontaminate water polluted by the organophosphorus phosalone. Phosalone was completely degraded in the presence of silver ions in a mole ratio of 7:1 in 20 min. Rainbow trout were divided into experimental groups to investigate the most effective ratio of silver/phosalone for pesticide degradation. Silver ion (2%) at a concentration of 0.75 and 0.1 mL removed phosalone (2%) at concentrations of 0.4 and 0.5 mL. All the rainbow trout survived in these two groups. This experiment suggested that silver ions can be beneficial at ratios in the range of 1:4 to 1:6 by hydrolyzing phosalone by attacking the electron-deficient phosphorus atom in the pesticide.

Risk Assessment of Florists Exposed to Pesticide Residues through Handling of Flowers and Preparing Bouquets

Flowers are frequently treated with pesticides and, as a result, florists handling daily a large number of flowers can be exposed to pesticide residues. A study was conducted among twenty volunteer florists located in Namur Province and in the Brussels Capital Region of Belgium in order to assess their potential dermal exposure to dislodgeable pesticide residues transferred from flowers to hands. Two pairs of cotton gloves were worn during two consecutive half days while handling flowers and preparing bouquets (from min 2 h to max 3 h/day). The residual pesticide deposits on the glove samples were extracted with a multi-residue Quick Easy Cheap Effective Rugged Safe (QuEChERS) method and analyzed by a combination of gas and liquid chromatography tandem mass spectrometry (GC-MS/MS and LC-MS/MS) by an accredited laboratory. A total of 111 active substances (mainly insecticides and fungicides) were detected, with an average of 37 active substances per sample and a total concentration per glove sample of 22.22 mg/kg. Several predictive levels of contamination were considered to assess the risk. The potential dermal exposures (PDE) of florists were estimated at the average, for different percentiles, and at the maximum concentration of residues in samples. At the PDE P90 and at the PDEMAX (or worst case) values, three and five active substances respectively exceed the Acceptable Operator Exposure Level (AOEL), indicating risk situations. For the systemic exposure (SE), one active substance (clofentezine) exceeds the AOEL at the P90 predictive level. In the worst case, SEMAX (at the maximum concentrations), four active substances (clofentezine, famoxadone, methiocarb, and pyridaben) exceed their respective AOEL values. Among the 14 most frequently detected active substances, two have SEMAX values exceeding the AOEL. Exposure could be particularly critical for clofentezine with an SEMAX value four times higher than the AOEL (393%). The exposure of florists appeared to be an example of a unique professional situation in which workers are exposed regularly to both a very high number of toxic chemicals and rather high concentration levels. Therefore the priority should be to raise the level of awareness among the florists who must change their habits and practices if they want to minimize their exposure.

Quick and label-free detection for Coumaphos by using surface plasmon resonance biochip

Coumaphos is a common organophosphorus pesticide used in agricultural products. It is harmful to human health and has a strictly stipulated maximum residue limit (MRL) on fruits and vegetables. Currently existing methods for detection are complex in execution, require expensive tools and are time consuming and labor intensive. The surface plasmon resonance method has been widely used in biomedicine and many other fields. This study discusses a detection method based on surface plasmon resonance in organophosphorus pesticide residues. As an alternative solution, this study proposes a method to detect Coumaphos. The method, which is based on surface plasmon resonance (SPR) and immune reaction, belongs to the suppression method. A group of samples of Coumaphos was detected by this method. The concentrations of Coumaphos in the samples were 0 µg/L, 50 µg/L, 100 µg/L, 300 µg/L, 500 µg/L, 1000 µg/L, 3000 µg/L and 5000 µg/L, respectively. Through detecting a group of samples, the process of kinetic reactions was analyzed and the corresponding standard curve was obtained. The sensibility is less than 25 µg/L, conforming to the standard of the MRL of Coumaphos stipulated by China. This method is label-free, using an unpurified single antibody only and can continuously test at least 80 groups of samples continuously. It has high sensitivity and specificity. The required equipments are simple, environmental friendly and easy to control. So this method is promised for a large number of samples quick detection on spot and for application prospects.

Environmental and biological monitoring in the estimation of absorbed doses of pesticides

Exposure to pesticides affects most of the population, not only persons occupationally exposed. In a context of high variability of exposure, biological monitoring is important because of the various routes by which exposure can occur and because it assesses both occupational and non-occupational exposure. The main aim of this paper was to critically compare estimates of absorbed dose measured by environmental and biological monitoring in situations in which they could both be applied. The combination of exposure measurements and biological monitoring was found to provide extremely important information on the behaviour of employees, and on the proper use and effectiveness of personal protection equipment.

Exposure to omethoate during stapling of ornamental plants in intensive cultivation tunnels: influence of environmental conditions on absorption of the pesticide

This report describes a study of exposure to omethoate during manual operations with ornamental plants in two intensive cultivation tunnels (tunnel 8 and tunnel 5). Airborne concentrations of omethoate were in the range 1.48-5.36 nmol/m(3). Total skin contamination in the range 329.94-12,934.46 nmol/day averaged 98.1 +/- 1.1% and 99.3 +/- 0.6% of the total potential dose in tunnel 8 and tunnel 5, respectively. Estimated absorbed doses during work in tunnel 5 were much higher than the acceptable daily intake of omethoate, which is 1.41 nmol/kg b.w. This finding shows that organization of the work or the protective clothing worn in tunnel 5 did not protect the workers from exposure. Urinary excretion of alkylphosphates was significantly higher than in the general population, increasing with exposure and usually showing a peak in the urine sample collected after the work shift. Urinary alkylphosphates showed a good correlation with estimated potential doses during work in tunnel 8 and are confirmed as sensitive biological indicators of exposure to phosphoric esters. The linear regression analysis between the urinary excretion of alkylphosphate, expressed as total nmol excreted in 24 h, and total cutaneous dose allows for estimating that the fraction of omethoate absorbed through the skin during work in tunnel 8 is about 16.5%.

Evaluation of skin and respiratory doses and urinary excretion of alkylphosphates in workers exposed to dimethoate during treatment of olive trees

This article describes a study of exposure to dimethoate during spraying of olive trees in Viterbo province in central Italy. Airborne concentrations of dimethoate were in the range 1.5 to 56.7 nmol/m(3). Total skin contamination was in the range 228.4 to 3200.7 nmol/d and averaged 96.0% +/- 3.6% of the total potential dose. Cotton garments afforded less skin protection than waterproof ones, which were in turn associated with higher skin contamination than disposable Tyvek overalls. Total potential doses and estimated absorbed doses, including their maxima, were below the acceptable daily intake of dimethoate, which is 43.6 nmol/kg body weight (b.w.). Urinary excretion of alkylphosphates was significantly higher than in the general population, increasing with exposure and usually showing a peak in the urine sample collected after treatment. Metabolite concentrations were influenced by the type of individual protection used: minimum levels were associated with the closed cabin and maximum levels with absence of any respiratory or hand protection. Urinary alkylphosphates showed a good correlation with estimated absorbed doses and are confirmed as sensitive biologic indicators of exposure to phosphoric esters.

Evaluation of respiratory and cutaneous doses of chlorothalonil during re-entry in greenhouses

Five female workers were monitored for 5 consecutive days during re-entry into a greenhouse containing ornamental plants. Skin contamination (excluding hands) was evaluated with nine pads of filter paper placed on the skin. Hand contamination was assessed by washing with 95% ethanol. Respiratory exposure was evaluated by personal air sampling. The respiratory dose was based on a lung ventilation of 15 l/min. The doses absorbed were estimated assuming 10% skin absorption and 100% lung retention. Dislodgeable foliar residue was determined on days of re-entry to evaluate the decay of chlorothalonil. Chlorothalonil was analysed in the different matrices by GC-MS. Respiratory exposure was less than skin contamination, being 11.4+/-5.1% (mean+/-SD) of total exposure. The estimated total absorbed dose did not exceed the acceptable daily intake of 0.03 mg/kg body mass. The hands and unexposed skin of all workers were always found to be contaminated. Greater precautions are therefore needed to reduce skin exposure (clean gloves and suitable clean clothing every day).

Development of an agricultural job-exposure matrix for British Columbia, Canada

Farmers in British Columbia (BC), Canada have been shown to have unexplained elevated proportional mortality rates for several cancers. Because agricultural exposures have never been documented systematically in BC, a quantitative agricultural Job-exposure matrix (JEM) was developed containing exposure assessments from 1950 to 1998. This JEM was developed to document historical exposures and to facilitate future epidemiological studies. Available information regarding BC farming practices was compiled and checklists of potential exposures were produced for each crop. Exposures identified included chemical, biological, and physical agents. Interviews with farmers and agricultural experts were conducted using the checklists as a starting point. This allowed the creation of an initial or 'potential' JEM based on three axes: exposure agent, 'type of work' and time. The 'type of work' axis was determined by combining several variables: region, crop, job title and task. This allowed for a complete description of exposures. Exposure assessments were made quantitatively, where data allowed, or by a dichotomous variable (exposed/unexposed). Quantitative calculations were divided into re-entry and application scenarios. 'Re-entry' exposures were quantified using a standard exposure model with some modification while application exposure estimates were derived using data from the North American Pesticide Handlers Exposure Database (PHED). As expected, exposures differed between crops and job titles both quantitatively and qualitatively. Of the 290 agents included in the exposure axis; 180 were pesticides. Over 3000 estimates of exposure were conducted; 50% of these were quantitative. Each quantitative estimate was at the daily absorbed dose level. Exposure estimates were then rated as high, medium, or low based on comparing them with their respective oral chemical reference dose (RfD) or Acceptable Daily Intake (ADI). This data was mainly obtained from the US Environmental Protection Agency (EPA) Integrated Risk Information System database. Of the quantitative estimates, 74% were rated as low (< 100%) and only 10% were rated as high (>500%). The JEM resulting from this study fills a void concerning exposures for BC farmers and farm workers. While only limited validation of assessments were possible, this JEM can serve as a benchmark for future studies. Preliminary analysis at the BC Cancer Agency (BCCA) using the JEM with prostate cancer records from a large cancer and occupation study/survey has already shown promising results. Development of this JEM provides a useful model for developing historical quantitative exposure estimates where is very little documented information available.

Ethylenethiourea in urine as an indicator of exposure to mancozeb in vineyard workers

In the present study, the personal exposure to mancozeb and/or ethilenethiourea (ETU) in 13 Italian vineyard workers and in 13 subjects without occupational exposure to pesticides was investigated. With this aim, the level of ETU in urine and the dermal exposure to mancozeb were determined. Baseline urinary ETU results were lower than the analytical limit of detection for all controls (<0.5 microg/g creatinine) and for ten workers (median <0.5, range <0.5-3.4 microg/g creatinine). In workers, urinary ETU was significantly increased at the end of shift (2.5, <0.5-95.2 microg/g creatinine) compared with baseline levels. End-shift urinary ETU was higher in operators using open tractors (n=7) than in those using closed tractors (n=5) (16.2 vs. 2.4 microg/g creatinine), but the difference was not significant (P=0.073). End-shift urinary ETU was positively correlated with dermal exposure to mancozeb determined both over the clothes and on the skin (Spearman's rho=0.770 and 0.702, P=0.009 and 0.024, respectively). Wine consumption positively influenced the excretion of ETU.

Persistence and performance of esfenvalerate residues on broccoli

The efficacy of esfenvalerate (84 g litre-1 EC; Asana XL) at 7.0 g AI ha-1 on broccoli was tested against the flea beetle, Phyllotreta cruciferae Goeze (Chrysomelidae: Coleoptera) and the imported cabbage worm, Pieris rapae L (Pieridae: Lepidoptera) under field conditions. Insect populations were monitored before and after treatment. Periodic sweep-net collections and examination of the leaves in treated and untreated broccoli plots revealed mean reductions of P cruciferae levels of nearly 98% 1 week post-application compared with untreated plots. The residual toxicity of esfenvalerate was also effective for 2 weeks in reducing population density of P rapae by 69% on broccoli leaves. The impact of esfenvalerate on feeding damage to broccoli leaves was established by counting the number of feeding holes made by P cruciferae on spring broccoli and P rapae on fall broccoli. As the leaf area ingested increased, a linear relationship was seen between the number of holes and number of insects. Results indicated that forage destruction by the two pests was significantly reduced by esfenvalerate application. Esfenvalerate was extracted from broccoli at 1 h and 1, 3, 7, 10, and 14 days post-application for residue analysis. Residues on spring broccoli were 12.2, 5.2 and 2.9 micrograms cm-2 on the leaves and 0.13, 0.05 and 0.02 microgram g-1 on the heads at 1 h, 1 and 3 days, respectively. Only trace levels (0.001 microgram g-1) were detected in/on the heads 14 days after spraying. On the basis of half-life (T1/2) values, persistence of esfenvalerate on spring broccoli leaves (T1/2 = 1 day) was shorter than on fall broccoli (T1/2 = 1.6 days). T1/2 values were 2.1 and 3.6 days on spring and fall broccoli heads, respectively. The implications of these residue levels on re-entry times into treated fields are discussed.

Neurophysiological function in farm workers exposed to organophosphate pesticides

To investigate neurophysiological effects of low-level exposure to foliar organophosphate residues during one season among agricultural workers, the authors performed a cross-sectional study of 67 Hispanic farm workers and 68 age-, gender-, ethnicity-, and education-matched reference subjects. The neurophysiological examination included sensory and motor nerve conduction and neuromuscular junction testing. Erythrocyte cholinesterase activity was measured at the time of examination. No statistically significant neurophysiological differences between the exposed and reference groups were observed. Farm workers and reference subjects had similar sensory nerve latency and amplitude (sural), motor nerve conduction velocity (ulnar), and neuromuscular junction function (ulnar). No relationship between duration of exposure during the season and electrophysiological measures of nerve function was found. Exposure of farm workers to the low levels of organophosphate pesticides during one season experienced by farm workers in this study was not associated with impaired peripheral neurophysiological function.

Paraquat Exposure of Knapsack Spray Operators on Banana Plantations in Costa Rica

A study of occupational exposure to paraquat was performed among 11 knapsack spray operators at banana plantations in Costa Rica. External and internal exposures were quantified and determinants of exposure identified by measurements, observations, and interviews. Dermal exposure was measured with skin pads, respiratory exposure by personal air sampling, and internal exposure by urine sampling. The wrists, back, and legs were the areas with the highest levels of dermal exposure. Respiratory exposures appeared to be strongly influenced by differences between days, while dermal exposures varied mostly due to differences between plantations. The use of protective clothing did not effectively protect against dermal exposures. Both respiratory and dermal exposures were significantly related to internal exposures, and both should be considered possible routes for systemic absorption of paraquat. It cannot be excluded that measurable levels of exposure can lead to acute as well as chronic health effects. Furthermore, due to poor conditions within the working environment, the spray operators are continuously at risk for high exposures that could lead to severe intoxication, and therefore a strategy for control of exposure is necessary.

Long vs. short monitoring intervals for peach harvesters exposed to foliar azinphos-methyl residues

A dermal monitoring study of peach harvesters exposed to azinphos-methyl (AM) residues was conducted in Sutter County, California. Harvesters were paid by piecework, which allowed characterization of the relationship between dermal exposure (DE) and time or production. Workers wore 2 long-sleeved knit T-shirts for each monitoring interval and also provided a hand residue sample. Dislodgeable foliar residue (DFR) samples were also collected. The highest correlations were found for inner shirts vs. production and DE vs. time worked (r2 = 0.67, P < 0.01). DE was greatest after 2-h exposures and reached equilibrium after 3 h, indicating that exposure estimates from shorter intervals would overestimate exposure.

Risk assessment of dermal exposure of greenhouse workers to pesticides after re-entry

On 18 farms for rose culture in greenhouses in The Netherlands, dermal exposure of hands and forearms to abamectin (avermectin B1), dodemorph (4-cyclododecyl-2,6-dimethylmorpholinium acetate) and bupirimate (5-butyl-2-(ethylamino)-6-methyl-4-pyrimidinyl dimethylsulphate) was measured during crop activities. Dermal exposure during cutting (75 workers) amounted to 13 micrograms/h, 1.8 mg/h, and 2.2 mg/h for abamectin, dodemorph and bupirimate, respectively. Dermal exposure to abamectin and dodemorph during sorting (21 workers) and bundling (30 workers) was comparable with that during cutting. From the dependence of dermal exposure on the amount of dislodgeable foliar residue (DFR) a transfer factor was estimated to be 1,200, 4,550, and 2,400 cm2/h for abamectin, dodemorph and bupirimate, respectively. For sorting and bundling these factors were of the same order of magnitude. The results suggested that work rate was also a determinant of dermal exposure. The within-farm variance of dermal exposure during cutting appeared to account for approximately 30% of the unexplained part of the variation remaining after regression on DFR and application technique. The final unexplained part in the variation of dermal exposure during cutting was amongst others due to the variation between the different farms in which the measurements were performed. A health risk evaluation of the observed levels of dermal exposure after re-entry of greenhouses led to the conclusion that a health hazard may exist, especially after application of high rates of relatively toxic pesticides which easily penetrate the skin.

Chlorothalonil exposure of workers on mechanical tomato harvesters

Worker exposure to chlorothalonil (tetrachloroisophthalonitrile, Bravo during mechanical tomato harvester operations of fruit for processing was estimated from passive dermal dosimetry monitoring (gauze pad and undershirt dosimetry), air concentration measurements and hand washes. Gauze pad dosimeters placed outside of workers' clothing gave an average potential dermal exposure of 499.6 micrograms/h. Dermal exposure based on undershirt dosimetry averaged 43.4 micrograms/h. Air concentrations ranged from 0.002-0.02 microgram/l. Dislodgeable fruit residues were measured and used to develop transfer factors (cm2 h) for both the pad dosimetry (450) and shirt dosimetry (40). Study results indicate that normal work clothing provides a 90% reduction in dermal exposure to chlorothalonil and that contribution of inhalation to total exposure ranges from 8.1-28%.

Effects of organophosphate insecticide residue variability on reentry intervals

A stochastic simulation program was written to study the importance of residue variability in predicting excessive chronic (seasonal) cholinesterase (AChE) inhibition and acute illness among a cohort of agricultural harvesters grouped into crews exposed to AChE-inhibiting insecticides. It was concluded that residue variability can substantially affect the cohort's AChE level only for daily mean AChE inhibitions below 4% per day, increasing end-of-season mean AChE inhibition but actually decreasing the cohort's end-of-season variability. The incidence of acute individual and group (crew) AChE inhibitions in excess of that potentially producing clinical symptoms (assumed herein to be greater than 50% in a day), exhibits a fairly clear boundary as a function of a combination of the residue's mean and deviation. The predicted acute response accurately parallelled reported rates, thus validating the simulation model.

Physical exercise affects cholinesterases and organophosphate response

1. Cholinesterase activities in blood and tissues of control and exercising rats with and without organophosphate (OP) exposure were studied. 2. Physical exercise increased total cholinesterase and butyrylcholinesterase activities in rats without OP exposure in blood and diaphragm. In brain physical exercise had no effect on acetylcholinesterase activity. 3. Physical exercise diminished cholinesterase inhibition in blood and tissues after OP exposure.