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Propanil is widely used as a postemergence herbicide in rice. Because it is typically applied aerially, there is a potential for propanil to drift into and around homes of those living adjacent to rice fields. Propanil has been shown to be immunotoxic in rodent models. The objective of this study was to measure the levels of propanil to which families living adjacent to aerially sprayed rice fields may be exposed. Air levels were sampled by actively and passively collecting propanil in and around the homes of volunteer families living in close proximity to rice fields sprayed with propanil. Homes ranged from 73 m to 113 m from treated rice fields. Sampling was conducted in the home, adjacent to the home (within 5 m of the home), 30 m from the home, and at the edge of the rice field. Concentrations were determined via gas chromatography/mass spectroscopy. Propanil levels adjacent to the homes ranged from nondetectable to 1,106.4 microg per 400 cm2 collection surface (2.0 microg detection limit). Wind direction and wind velocity were the primary determinants of propanil drift. At sites where the prevailing wind was blowing away from the home, no propanil was detected except at the edge of the field. Distance from the edge of the rice field also influenced the amount of drift with higher levels measured at 30 m from the house than adjacent to the house. No propanil vapor was detected on absorbent media sampled in and around the homes. The results indicate that individuals living adjacent to rice fields aerially sprayed with propanil are potentially exposed to variable amounts of propanil, and wind speed and direction are the most important factors that influence the concentration of aerially applied pesticide.

Field studies were conducted on silt laom and silty clay soils to determine the persistence of carbofuran (2,3-dihydro-2,2-dimethyl-benzofuran-7-yl-methylcarbamate) and molinate (S-ethyl hexahydro-1H-azepine-1-carbothioate) in the soil and water associated with rice (Oryza sativa L.) production in Arkansas. Paddy-rice plots were established with earthen levees surrounding each plot and standard cultural practices were followed concerning rice population. Granular formulations of these pesticides were applied 4 d following establishment of the permanent flood at the tillering stage of rice growth. Samples of water and soil were taken at various intervals until 49 days after application (DAA) and analyzed with gas chromatography. Carbofuran was not detected in paddy water after 28 DAA. By 21 DAA, >90% of the applied molinate had dissipated, but detectable levels (0.0012 mg L -1 ) of residues remained in paddy water through 49 DAA. Both pesticides dissipated rapidly from paddy soil for approximately the first 14 DAA, probably due to solubilization of the granules into the overlying paddy water. Both the pesticides has estimated time required for dissipation of 50% of the initial concentration (DT 50 s) of 10 d in paddy water and paddy soil. Molinate dissipation from paddy soil slowed dramatically after the initial rapid phase. The carbofuran metabolite 3-keto carbofuran (2,3-dihydro-2,2-dimethyl-3-keto-benzofuran-N-methyl carbamate) was not detected in any water samples, but was detected in 6% of the soil samples. The metabolites 3-hydroxy carbofuran (2,3-dihydro-2,2-dimethyl-3-hydroxy-benzofuranyl-N-methyl carbamate) was detected in 2% of the water samples and 7% of the soil samples. In both cases the concentrations found were slightly above the lower limits of detectability (0.005 mg L -1 for water and 0.01 mg kg -1 for soil)

Data are lacking concerning the persistence of pesticides used in Arkansas rice production. Studies were conducted to examine the dissipation characteristics in field studies of four commonly used pesticides (.)

This study addresses the measurements of glyphosate exposure received by 14 workers employed at two tree nurseries. The applicators, weeders, and scouts monitored all wore normal work clothing, which for applicators was a protective suit, rubber gloves and boots. Measurements were made of the glyphosate that was dislodged from conifer seedlings during water rinses taken twice weekly from May through August. Only 1 of these 78 dislodgeable residue samples were positive for glyphosate. Nine cotton gauze patches were attached to the clothing of each worker one day per week during this same period. Hand washes were taken on the same day that patches were worn. Most patches and hand washes from applicators and weeders contained measurable amounts of glyphosate. Analyses of individual patches showed that the body portions receiving the highest exposure were ankles and thighs. For scouts only 1 of 23 hand washes contained glyphosate. To provide a measure of the exposure occurring via all exposure routes (dermal, ingestion, and inhalation) an analysis was made of the total urine excreted. For most workers a daily total urine collection was made for 12 consecutive weeks. Urine analysis, the biological monitoring tool used to assess the total amount absorbed via all avenues, did not reveal any positive samples. The lower limit of method validation for glyphosate in the urine samples was 0.01 micrograms/ml. High rainfall, or irrigation as needed, in conjunction with normal field dissipation avenues and worker training were cited as contributing factors for the low amounts of glyphosate exposure found.(ABSTRACT TRUNCATED AT 250 WORDS)

This study was conducted to determine the stability of five commonly used herbicides fortified into freshly collected ground water. No aquifer materials were present. Ground-water samples obtained from three sites in eastern Arkansas were fortified with an aqueous mixture containing either the chloroacetamide herbicides, alachlor, metolachlor, and propanil, or the phenoxy herbicides, 2,4-D and dichlorprop. Experiments were conducted at tempersitures comparable to Arkansas' extreme ground-water temperatures, 15 and 22° C, and at initial concentrations of 1 and 5 μg/1. Degradation occurring for each herbicide was determined at two-month intervals, for a period of 18 months. Results indicated that degradation did not begin immediately, but generally required a lag period of several months. Of the five herbicides studied, propanil degraded the fastest and to the greatest extent. After eight months, 44% to 69% of propanil at the lower fortification level and 85% to 99% at the higher level had degraded, The remaining four herbicides exhibited little or no degradation at the lower concentration during the first 12 months. By 18 months, however, significant degradation of each herbicide had occurred. Degradation generally occurred earlier for each herbicide at the higher fortification level. With the exception of 2,4-D, a higher percentage of herbicide was broken down at the greater fortification level. Degradation was more extensive at the elevated storage temperature. In general, the degradation rate was faster in ground water taken from shallower depths. Zero-order rate constants and half-lives are presented. Half-lives, including lag periods, ranged from 196 to 1907 days.

Deposits of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from both pressure-atomized and Visko-Rhap invert emulsion equipment were measured on vertical plastic targets from the spray swath to 549 m (1800 ft) downwind. The quantity of 2,4-D deposited at 15 m downwind from a fixed-wing aircraft using the invert under windy conditions was 47% of that from the pressure-atomized spray. At 549 m, the deposit from the invert averaged 5% of that from the spray. Equations for predic-tion of deposition given distance from the spray swath were developed for both application methods. For this invert system, one half to one third of the required (Arkansas) 1609 nl (1 mi) spray buffer provided chemical deposition equivalent to that from the pressure-atomized spray. Deposition.fruit would be located.system performed reliably at a sustained harvesting rate of approximately 1.4 ha/day (3.4 acre/day), while indicating that a rate of 2 ha/day (5 acre/day) should be easily achievable. The system is operated by two workers and reduces conventional labor requirement by approximately 80-85%.

Two-year-old highbush blueberry bushes (Vaccinium corymbosum L. `Collins') were treated in Mar. 1985 with diuron or simazine at 2.2 or 4.5 kg a.i./ha. No residues were detected by reverse-phase high-performance liquid chromatography-ultraviolet absorbance detection (HPLC-UV) from treated berries that were harvested in June. Methiocarb was applied in May 1986 at 0.84 and 3 kg·ha-1 over the top of 3-year-old `Collins' when the berries began to ripen. Reverse-phase HPLC-UV of berries treated with methiocarb at 3 kg·ha-1 had combined residues of methiocarb and its sulfone and sulfoxide metabolites of 13.1 ppm from unrinsed and 7 ppm from rinsed berries harvested on the day of treatment; 4.9 ppm from unrinsed and 4 ppm from rinsed berries harvested 4 days after treatment; and 2.4 ppm from unrinsed and 2.5 ppm from rinsed berries harvested 8 days after treatment. Unrinsed berries treated with methiocarb at 0.84 kg·ha-1 had 5.7 ppm residue on the day of treatment and 1 ppm 8 days later. Residues from berries treated with methiocarb at 0.84 or 3 kg·ha-1 were below the legal tolerance level of 5 ppm after the required 7-day waiting period. Chemical names used: n'-(3,4-dichlorophenyl)-N,N -dimethylurea (diuron); 6-chloro- N,N' -diethyl-1,3,5-triazine-2,4-diamine (simazine); 3,5-dimethyl-4-(methylthio)phenol methylcarbamate (methiocarb).

Epidemiologic studies of potential health effects resulting from exposure to one or multiple pesticides are strengthened by the use of biological markers, such as internal dose markers, to more accurately classify individual exposures. Additionally, measures of internal body dose are also useful to establish guidelines for field reentry and protective clothing or practices, and to enable early detection of exposure circumstances in worker safety programs. This chapter explores the concepts of exposure biomarkers, focusing on their past and potential application to studies of pesticide exposures.

Greenhouse and field studies demonstrated that plants compete for soil-applied atrazine (2-chloro4-(ethylamino)-6-(isopropyl- amino)-s-triazinel. Oats (Avena sativa L. 'Neal') and soybeans (Glycine max (L.) Merr. 'Clark 63') were grown in greenhouse bioassay studies to study the effects of plant population on bioassay sensitivity. High plant populations were not as effective as low plant populations in detecting low levels of atrazine in soil. Conversely, by increasing plant populations or decreasing soil volumes quantitative measurement of higher atrazine concentrations can be determined. A lC-labeled atrazine study showed that by increasing soybean populations from one to six per pot, atrazine uptake per plant was decreased 50%. When soybeans were planted at a rate of six plants per 100 cm2 in a field treated with atrazine at 1.1 kg/ha, soybean dry weight production was 97% of the untreated control; when planted at a rate of one plant per 100 cm2, dry weight was only 26% of the comparable untreated check. Thus, herbicide rates for optimum weed control may have to be increased with increasing weed populations or increased crop seeding rates or both. 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, and 1.0 ppmw except where noted on specific experiments. The bioassay crops were grown in 10 cm tall polyethylene pots in a fiberglass greenhouse maintained between 22 and 31 C. Supplementary lighting provided a day length of 16 h in the range of 0.4 to 0.6 microeinsteins intensity. Pots were watered by alternate surface watering and subirrigation. The plant yields were determined after harvesting the above ground portion and oven drying 48 h at 80 C. The experimental designs, except where noted, were ran- domized complete block with four replications. The data were

The concentration of hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] in soil, water, and plant tissue was monitored following hexazinone application (2.0 kg a.i./ha) to an 11.5-ha watershed in northwestern Arkansas. The hexazinone concentration in the top 10 cm of soil on the watershed decreased to approximately 10% of the initial concentration in 42 d. Hexazinone dissipation rate on the watershed was more rapid than could be accounted for solely by degradation. Leaching of hexazinone to lower soil depths probably was important to hexazinone dissipation. Hexazinone degradation in soil incubated at 10 and 30°C followed first-order kinetics and had a half-life of 77 d at 30°C. Hexazinone was stable in incubated stream water requiring several years for 50% disappearance of the compound at 30°C. The maximum hexazinone concentration in the stream that drained the watershed was 14 µg/L, and hexazinone residues (< 3 µg/L) were detected in stream discharge over 1 yr after application. The amount of hexazinone transported from the watershed in stream discharge represented 2.0 to 3.0% of the amount of initially applied. Analyses of oak foliage and leaf litter collected from the forest floor indicated that < 0.10% of the hexazinone applied was returned to the forest floor in leaf deposition.

During 1985 to 1987, 119 wells, Springs and municipal drinking water supplies throughout Arkansas were monitored for the presence of pesticides. Pesticides selected for analysis included acifluorfen, alachlor, aldicarb, atrazine, benomyl, cyanazine, cypermethrin, 2,4-D, dichlorprop, diuron, fenvalerate, fluometuron, hexazinone, linuron, metolachlor, permethrin, picloram, and propanil. Not every sample was analyzed for every pesticide. Overall, results indicated that the 18 herbicides, fungicides, and insecticides were not present in the ground water samples studied. (Note: Detectable concentrations of three herbicides – alachlor, atrazine, and metolachlor – were found in one irrigation well, at 5.5,5.8, and 6.9 μg/L, respectively. However, since previous and subsequent sampling failed to detect these compounds, their presence is attributed to a localized spill or handling error rather than agricultural application.)

The adsorption of atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine] was measured on soil at water:soil ratio of 5:1 and 0.4:1. The adsorption isotherms for atrazine were described by the Freundlich equation. A decrease in water:soil ratio and in soil moisture content led to an increased adsorption of the herbicide. Increasing the concentration of electrolytes in the soil solution by adding solutions up to 0.1M CaCl2increased atrazine adsorption. Greater amounts of atrazine were adsorbed at 30 than at 5 C on four soils at 0.1 bar moisture content. This indicates an endothermic reaction which was observed both before and after correction for differential atrazine solubility due to temperature. Thermodynamic quantities associated with the adsorption reaction were calculated to characterize the adsorption of atrazine on soil.

A pyrethrin drench appeared to be as efficient as or more efficient than soil sifting as a method of detecting adult alfalfa weevils, Hypera postica (Gyllenhal), in the soil. Adult weevils fed on cut alfalfa treated with 32P were labeled and could be detected in the field for at least 6 wk. The procedures were used to determine that most adult weevils left the study field during the month following 1st harvest for more sheltered locations, but they were not found congregated in any single location.

Urine samples from 80 forest workers applying 2,4-D [(2,4-dichlorophenoxy)acetic acid] plus dichlorprop [(±)-2-(2,4-dichlorophenoxy)propanoic acid] or picloram (4-amino-3,5,6-trichloro-2-pyridinecarboxylic acid) by ground techniques were monitored to determine the dose of chemical absorbed. Four crews of 20 workers each were studied to compare the exposures during application by backpack, injection bar, Hypohatchet or a hack-and-squirt method. Total urine output was analyzed to compare the absorbed dose to each worker under two operational modes. In the first, designated T-1, the workers wore their usual clothing and followed the work habits they ordinarily used on the job. In the second mode, designated T-2 and conducted 6 d after the first, workers were given new leather gloves and boots and asked to take all feasible precautions to prevent herbicide exposure and to wash immediately if they come into contact with the chemical. For all application methods except that with backpacks, the T-2 treatment decreased the absorbed dose. During both T-1 and T-2 the clothing of backpack sprayers often became saturated with spray, dew or perspiration, and these workers received a higher absorbed dose of 2,4-D (0.04–0.24 mg/kg body weight) than did workers in other crews. The absorbed dose of dichlorprop ranged from undetectable to 0.18 mg/kg. Hypohatchet workers received a greater dose than did injection bar or hack-and-squirt workers. The absorbed dose of picloram ranged from undetectable to 0.02 mg/kg. If equal dermal penetration of 2,4-D and picloram is assumed, this represents much less dermal absorption than would have been predicted from the relative amounts of 2,4-D and picloram in Tordon 101-Rr.

Microbial degradation of imazaquin {2-[4,5-dihydro-4-methyl-4-(1-methylethyl)-5-oxo-1H-imidazol-2-yl]-3-quinolinecarboxylic acid} was monitored by measuring14CO2evolution for 7 months under controlled laboratory conditions. Up to 10% of the14C chain-labeled imazaquin that was applied to a Crowley silt loam was evolved as14CO2in 7 months. Less evolution of14CO2occurred on a Sharkey silty clay, a soil with higher clay and organic matter content, than on silt loam soils. The loss of 66 to 100% of the imazaquin applied to a Crowley silt loam incubated for 8 months at 18 C or 35 C, respectively, suggested that metabolic changes in addition to CO2evolution were occurring. Rapid loss of imazaquin phytotoxicity occurred when soils were held at warm-moist (35 C and −33 kPa) conditions conducive to microbial growth. Imazaquin was more persistent in soils stored under cool, dry (18 C and −100 kPa) conditions. Imazaquin on a soil surface dissipated rapidly when exposed to ultraviolet light or sunlight. Photodecomposition could be a major mode of imazaquin dissipation if this herbicide is allowed to remain on the soil surface.

The objective of this study was to determine effects of pretreatment, equilibrium time, and concentration on adsorption of the labile organic chemical phenol by two soils: Captina silt loam (Typie Fragiudult) and Palouse silt loam (Ultic Haploxeroll). Adsorption of phenol by soil was determined by radioassay using the batch technique. Since loss from solution is equated with adsorption with the batch method, degradation of phenol is also recorded as adsorption. Adsorption of phenol was low, as evidenced by Freudlich K values of 0.57 and 1.19 for the sterile Captina and Palouse soils, respectively. The addition of water, glucose, or nutrient broth to the non-sterile soil increased the apparent adsorption by reducing the phenol concentration in the solution phase. As equilibration time increased, the apparent adsorption of phenol by the non-sterile soil also increased. When compared with the sterilized soil, this increase suggested that the loss of phenol from solution was largely due to microbial decomposition. As the concentration of phenol increased, there was a corresponding increase in the lag phase and a decrease in the degradation rate constant indicating inhibition and microbial activity by phenol at higher concentrations. The length of time in the lag phase was linearly related tomore » the log of the phenol concentration. At a given concentration, the lag phase of the Captina soil was longer and more sensitive to changes in phenol concentration than was the lag phase in the Palouse soil. This was attributed to its lower phenol adsorption, organic matter content, and initial microbial population.« less

Root and shoot extracts of 3-week-old sudangrass [Sorghum sudanense(Piper) Stapf, var. Piper], grain sorghum [Sorghum bicolor(L.) Moench], and corn (Zea maysL.) plants degraded 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) in order: shoot > root and corn ≫ sorghum = sudangrass. In 3-week-old detopped plants, the rate of atrazine exudation was 14 times greater in sudangrass and sorghum than in corn when grown in Keith sandy loam containing 0.5 ppmw14C-atrazine. Extraction and analysis of plant shoots revealed that 7 to 8% of the14C was present as atrazine in sudangrass and sorghum whereas no atrazine was found in corn. In14C tracer studies, thin-layer chromatography showed that sudangrass and sorghum metabolized atrazine by a pathway which differed from the pathway in corn. Sudangrass and sorghum metabolized atrazine primarily to 2-chloro-4-amino-6-(isopropylamino)-s-triazine and 2-chloro-4-amino-6-(ethylamino)-s-triazine which are only partially detoxified compounds. Corn metabolized atrazine to 2-hydroxy-4-(ethylamino)-6-(isopropylamino)-s-triazine (hydroxyatrazine) which is non-phytotoxic.

Degradation of 2-chloro-4-ethylamino-6-isopropyl-s-triazine (atrazine) was studied in the 0 to 9, 14 to 24, and 36 to 48-inch depths of Sharpsburg silty clay loam and Keith silt loam soils. The effects of moisture, temperature, and microorganisms on degradation were observed. Atrazine was degraded two to three times faster in the topsoils than in the subsoils. Each 10 C temperature increase from 15 to 35 C caused the degradation rate to increase two to three times in these soils. Increasing the moisture content of the soils from 0.4 to 0.8 field capacity caused 14CO2 evolution from chain-labeled atrazine-14C treated soils to increase zero to six times. At 25 C and 0.8 field capacity, 100 to 194 atrazine molecules were detoxified for each molecule evolved as 14CO2 from chain-labeled atrazine. Solution culture studies showed cleavage of the side chain and ring of atrazine-14C except in the 14 to 24 and 36 to 48-inch depths of Keith silt loam.

Soil from three depths was treated with (2,4-dichlorophenoxy) acetic acid (2,4-D) and 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) and buried in the soil profile for 5, 17, 29 and 41 months at two locations in Nebraska. Degradation of 2,4-D stored in field pits at 15-, 40-, and 90-cm depths was rapid under aerobic soil conditions at both locations. Rates of atrazine degradation decreased with increasing soil depths. In Sharpsburg silty clay loam, phytotoxic amounts of atrazine dissipated during the first 5 months at the 15-cm depth, and during the first 17 months at the 40-cm depth. Atrazine treated samples buried at 90 cm in the same profile contained phytotoxic amounts of atrazine after 41 months as shown by a soybean bioassay and gas chromatographic analysis.

The uptake of 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine) was studied in sudangrass [Sorghum sudanense(Piper) Stapf, var. Piper], grain sorghum [Sorghum bicolor(L.) Moench], and corn (Zea maysL.) to find whether differences in atrazine uptake exist among these species. The uptake of atrazine followed closely the growth patterns of corn, sorghum, and sudangrass during the first 5 weeks of growth. Concentration of14C from ring-labeled14C-atrazine in the soil reached a peak in corn, sorghum, and sudangrass plants after 2 weeks of growth and then declined. The14C concentrations were two to three times greater in sorghum and sudangrass than in corn throughout the 5-week period. Atrazine uptake per gram of plant growth by these crops was directly proportional to the concentration of atrazine in the soil and the proportionality factors were in the order: sudangrass < sorghum ≫ corn. Total uptake and the total growth were in order: corn ≫ sorghum = sudangrass. In a study where relative humidity was a variable, the amount of atrazine absorbed per ml of water was inversely related to total water usage.

In laboratory studies with 3-amino-2,5-dichlorobenzoic acid (amiben), adsorption of 14C-amiben was less than 14C-amiben methyl ester with all adsorbents tested. Adsorption of 14C-amiben was closely associated with soil organic matter. Also, considerable adsorption of 14C-amiben and 14C-methyl ester was observed on illite clay and on Sassafras loamy sand which contains clay minerals composed primarily of illite clay. Root uptake of amiben caused more injury than shoot uptake to greenhouse-grown corn (Zea mays L., var. Nebraska 202). The relatively insoluble butoxy ethyl ester of amiben was the most toxic amiben derivative to greenhouse-grown corn. Subirrigation moved the more soluble amiben derivatives to the soil surface where they had less effect on the root system. In field studies comparing four derivatives of amiben applied preemergence to corn in 1966, best weed control was from the ammonium salt of amiben at 2 and 4 lb/A and the methyl and butoxy ethyl ester at 4 lb/A; the amide was ineffective. The ammonium salt of amiben caused early stunting of corn but did not reduce yield. Selective weed control in soybeans [Glycine max (L.) Merr., var. Clark] was obtained in 1966 with the ammonium salt, 80% wettable powder, and monomethyl amine salt of amiben at 1 1/2 lb/A, and the methyl and butoxy ethyl ester at 6 lb/A. In 1967, the best amiben derivatives for weed control in soybeans were the amide and esters. Amiben derivatives more susceptible to leaching were less effective in controlling weeds in 1967 due to excessive rainfall after amiben applications.

A liquid scintillation counting solution was developed which optimized the direct assay efficiencies of14C-labeled 2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triazine (atrazine), 3,6-dichloro-o-anisic acid (dicamba), and α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) in soil. In this counting technique, 3-g soil samples containing14C-labeled herbicide were placed directly into a liquid scintillation vial containing a phosphorescent counting solution. Samples were shaken and allowed to settle before assaying using a liquid scintillation spectrometer. This direct radioassay was as efficient or more efficient than double or single extraction processes. Automatic external standardization in conjunction with the liquid scintillation counter was an effective tool for estimating the14C present in soil samples.

Atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-s-triaazine] diffused at a rate of 15.2 × 10−8sq cm/sec at 25 C which was faster than the diffusion rate of 2-chloro-4,6-bis(ethylamino)-s-triazine (simazine) and 2-chloro-4,6-bis(isopropylamino)-s-triazine (propazine) in the same soils. Diffusion rates were highly correlated with total surface area of the soil. Increasing soil moisture content, soil pH, and soil temperature resulted in greater diffusion rates. A relative indication of herbicide mobility may be obtained from some of the physical and chemical properties of the soils and herbicides involved; however, rate of diffusion appears to be governed by a combination of soil and herbicide properties.

Phytotoxicity of α,α,α-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin), incubated for 10 months in Sharpsburg silty clay loam at 0.8 field capacity, remained a 6.4, 0, and 1.6 ppmw of the original 8 ppmw at 15, 25, and 35 C, respectively. In Anselmo sandy loam after 10-months incubation, trifluralin phytotoxicity remained at 3.0, 3.2, and 0.6 ppmw of the original 4 ppmw at 15, 25, and 35 C, respectively. Breakdown of 14C-trifluralin to 14CO2 in both soils was more rapid at 1.6 field capacity than at 0.8 field capacity, and at 1 ppmw than at 100 ppmw of trifluralin. Breakdown of 14C-trifluralin to 14CO2 accounted for 5 and 3% of the decrease of 14C-activity in Sharpsburg silty clay loam and Anselmo sandy loam, respectively.

Dissipation of 2-methoxy-3,6-dichlorobenzoic acid (dicamba) was greater in Sharpsburg silty clay loam soil than in Anselmo sandy loam soil and was faster in the topsoil than in the subsoil. Breakdown increased with increasing soil incubation temperatures. Phytotoxicity of dicamba and 3-amino-2,5-dichlorobenzoic acid (amiben) in aqueous solutions decreased upon exposure to sunlight. Amiben was more susceptible to photodecomposition than was dicamba. Aqueous dicamba solutions exposed to sunlight for 16 days decreased growth of cucumber (Cucumis sativus L.) seedlings, while amiben solutions caused no growth reduction after 2 days' sunlight exposure. Dicamba solutions exposed to 60 C showed increased phytotoxicity while amiben solutions were unaffected. Dicamba was most phytotoxic to corn (Zea mays L.) seedlings at pH 4 and to cucumber seedlings at pH 5. Dicamba solutions were taken up by both shoots and roots of corn and cucumber seedlings; however, root uptake resulted in greater growth reductions.

Monitoring soils for persistent pesticides residues requires accurate and sensitive analytical methods. Residue extraction, the first step in a long multi-stage procedure, is as important as the subsequent analyses because residues that are not extracted are not measured. Similarly, erroneous monitoring data of industrial contaminants in the environment could result if ineffective extraction procedures are used. Important to the final results of a residue analysis are the collection of the soil sample, storage, the degree of weathering or aging of the sample, preparation prior to extraction, soil texture, water content of the soil sample, the organic solvent used, solvent-soil contact time, mechanical handling of the mixture (stripping), and the amount of co-extractives and the nature of their interference.

A campaign to educate the public regarding the merits of pesticides is necessary if we are to overcome the widespread poor image of pesticides that exists in society today. A comparison of biological monitoring and measurements of pesticide deposition on patches suggests that since only the absorbed dose has any potential for adverse health effects if forced to choose one technique over the other, more emphasis should be placed on biological monitoring. Controlled human pesticide exposure and dermal absorption studies establishing pharmacokinetic data are necessary if scientists and regulatory officials are expected to make knowledgeable worker safety recommendations pertaining to the pesticides being used today. Worker exposure can continue beyond the application day if pesticide-contaminated boots or gloves are used later. Excretion rate of 2,4-D in human urine was not affected by the presence of picloram in the application mixture. Margins of safety guidelines are highly dependent on adoption of appropriate no observed effect levels (NOEL).

Several Arkansas commercial grape growers operating tractor-mounted, low-boom vineyard spray rigs were monitored for potential dermal, respiratory, and internal exposure to paraquat (1-1′-dimethyl-4,4′-bipyridinium ion) during the 1980 and 1981 growing seasons. Workers followed their usual mixing and spraying routines with as little influence as possible from the test. Analyses by colorimetric methods revealed very low levels of paraquat exposure. Greatest dermal exposure levels averaging 0.015 mg paraquat/kg body weight were detected on persons operating the spray rigs. Respiratory exposure was minimal and there was no paraquat detected in any of the urine samples collected from each worker. Those persons receiving the highest levels of paraquat exposure had measurements which were well below those found to be toxic to laboratory animals. Hazards from using this material by this method of application should be low when used in accordance to label directions and precautions.