Evaluation of an alternative sorbent for passive sampling of the herbicides 2,4-D and Dicamba in the air.

The present study aimed to evaluate the Strata-X® sorbent, commonly used in cartridges, through analysis by high-performance liquid chromatography coupled with mass spectrometry. Due to the different physical-chemical characteristics of the compounds, different conditions of chromatography and mass analysis were necessary. The developed methods were validated in terms of selectivity, linear range, linearity (coefficient of determination, r2), the limit of detection (LOD), the limit of quantification (LOQ), accuracy (recovery, %), and precision (RSD, %). The results allowed us to select efficient extraction methods, using methanol acidified to pH 2 with formic acid, to elute the herbicides 2,4-D and dicamba in both sorbent materials. Besides, the Strata-X® sorbent was efficient in the sorption of analytes; thus, we indicate it for potential use in air sampling as an alternative to XAD-2.

Evaluation of a Stable Isotope-Based Direct Quantification Method for Dicamba Analysis from Air and Water Using Single-Quadrupole LC-MS.

Dicamba is a moderately volatile herbicide used for post-emergent control of broadleaf weeds in corn, soybean, and a number of other crops. With increased use of dicamba due to the release of dicamba-resistant cotton and soybean varieties, growing controversy over the effects of spray drift and volatilization on non-target crops has increased the need for quantifying dicamba collected from water and air sampling. Therefore, this study was designed to evaluate stable isotope-based direct quantification of dicamba from air and water samples using single-quadrupole liquid chromatography-mass spectrometry (LC-MS). The sample preparation protocols developed in this study utilize a simple solid-phase extraction (SPE) protocol for water samples and a single-step concentration protocol for air samples. The LC-MS detection method achieves sensitive detection of dicamba based on selected ion monitoring (SIM) of precursor and fragment ions and relies on the use of an isotopically labeled internal standard (IS) (D3-dicamba), which allows for calculating recoveries and quantification using a relative response factor (RRF). Analyte recoveries of 106-128% from water and 88-124% from air were attained, with limits of detection (LODs) of 0.1 ng mL-1 and 1 ng mL-1, respectively. The LC-MS detection method does not require sample pretreatment such as ion-pairing or derivatization to achieve sensitivity. Moreover, this study reveals matrix effects associated with sorbent resin used in air sample collection and demonstrates how the use of an isotopically labeled IS with RRF-based analysis can account for ion suppression. The LC-MS method is easily transferrable and offers a robust alternative to methods relying on more expensive tandem LC-MS/MS-based options.

Dicamba and 2,4-D residues following applicator cleanout: A potential point source to the environment and worker exposure.

UNLABELLED: This paper presents a survey of pesticide residues in tanks following application and throughout the cleanout procedure as conducted by 46 volunteer operators across Colorado. While many pesticides were detected, this paper focuses on dicamba and 2,4-D, which were detected by liquid chromatography/tandem mass spectroscopy (LC-MS/MS). An exponential decrease in concentration was observed with sequential rinses, although this decrease may be more rapid for more water-soluble pesticides. More than 95% of the pesticide in the prerinse solution was removed by the end of the third rinse in all but three operator samples. Concentrations after three rinses were 0.41 ± 0.25 and 3.3 ± 1.1 mg/L for dicamba and 2,4-D, respectively. These concentrations suggest that the recommended practice of three rinses may not be adequate to eliminate off-target effects or point sources of pesticide waste, and that the recommended standard of personal protective equipment is essential to prevent worker exposure to the chemicals. IMPLICATIONS: This paper demonstrates that the waste generated during cleanout of pesticide application devices constitutes a potential source of pollution and worker exposure. In particular, while the first rinse of pesticide containers is often treated as hazardous waste and reapplied to crops, the remaining rinses are not. This work demonstrates that the wastewater generated in subsequent rinses can have high enough concentrations to impact worker health, cause off-target effects on crops, and potentially constitute a point source of pesticides. The practical implication is for improved recommendations and regulations regarding pesticide applicators and their cleanout process.

On-line monitoring of the photocatalytic degradation of 2,4-D and dicamba using a solid-phase extraction-multisyringe flow injection system.

A fully automated on-line system for monitoring the photocatalytic degradation of herbicides was developed using multisyringe flow injection analysis (MSFIA) coupled to a solid phase extraction (SPE) unit with UV detection. The calibration curves were linear in the concentration range of 100-1000 µg L(-1) for 3,6-dichloro-2-methoxybenzoic acid (dicamba) and 500-3000 µg L(-1) for 2,4-dichlorophenoxyacetic acid (2,4-D), while the detection limits were 30 and 135 µg L(-1) for dicamba and 2,4-D, respectively. The monitoring of the photocatalytic degradation (TiO2 anatase/UV 254 nm) of these two herbicides was performed by MSFIA-SPE system using a small sample volume (2 mL) in a fully automated approach. The degradation was assessed in ultrapure and drinking water with initial concentrations of 1000 and 2000 µg L(-1) for dicamba and 2,4-D, respectively. Degradation percentages of approximately 85% were obtained for both herbicides in ultrapure water after 45 min of photocatalytic treatment. A similar degradation efficiency in drinking water was observed for 2,4-D, whereas dicamba exhibited a lower degradation percentage (75%), which could be attributed to the presence of inorganic species in this kind of water.

Applicability of multisyringe chromatography coupled to on-line solid-phase extraction to the simultaneous determination of dicamba, 2,4-D, and atrazine.

Simultaneous determination of three herbicides (dicamba, 2,4-D, and atrazine) has been achieved by on-line solid-phase extraction (SPE) coupled to multisyringe chromatography (MSC) with UV detection. The preconcentration conditions were optimized; a preconcentration flow rate of 0.5 mL min(-1) and elution at 0.8 mL min(-1) were the optimum conditions. A C(18) (8 mm i.d.) membrane extraction disk conditioned with 0.3 mol L(-1) HCl in 0.5% MeOH was used. A 3-mL sample was preconcentrated, then eluted with 0.43 mL 40:60 water-MeOH. A C(18) monolithic column (25 mm × 4.6 mm) was used for chromatographic separation. Separation of the three compounds was achieved in 10 min by use of 0.01% aqueous acetic acid-MeOH (60:40) as mobile phase at a flow rate of 0.8 mL min(-1). The limits of detection (LOD) were 13, 57, and 22 µg L(-1) for dicamba, 2,4-D, and atrazine, respectively. The sampling frequency was three analyses per hour, and each analysis consumed only 7.3 mL solvent. The method was applied to spiked water samples, and recovery between 85 and 112% was obtained. Recovery was significantly better than in the conventional HPLC-UV method. These results indicated the reliability and accuracy of this flow-based method. This is the first time this family of herbicides has been simultaneously analyzed by on-line SPE-MSC using a monolithic column.

Simultaneous determination of three acidic herbicide residues in food crops using HPLC and confirmation via LC-MS/MS.

2,4-D, dicamba and 4-CPA with auxin-like activity have been intensively used in agriculture, for the control of unwanted broadleaf weeds. An analytical method involving HPLC coupled with UVD was developed for the simultaneous analysis of these three analytes in Chinese cabbage, apple and pepper fruits (representative non-fatty samples) and brown rice and soybean (representative fatty samples) using liquid-liquid partitioning and column cleanup procedures. The residues were confirmed via tandem mass spectrometry (MS/MS) in ion electrospray ionization (ESI) mode. The standard curves were linear over the range of the tested concentrations (0.25-10 microg/mL), as shown by a marked linearity in excess of 0.9999 (r(2) ). The average recoveries (mean, n = 3) ranged from 94.30 to 102.63 in Chinese cabbage, from 94.76 to 108.47 in apple, from 97.52 to 102.27 in pepper, from 76.19 to 101.90 in brown rice, and from 74.60 to 107.39 in soybean. The relative standard deviations (RSDs) were <9% in all tested matrices. The limits of detection and quantitation were 0.006 and 0.02 mg/kg, respectively. Samples purchased from local markets were analyzed to evaluate the applicability of the methods developed herein. The concentration of the 2,4-D residue was measured at 0.102 mg/kg in the soybean sample; however, this level is exactly the same MRL set by the Korea Food and Drug Administration. This developed method deserves full and complete consideration, as it clearly displays the sensitivity, accuracy and precision required for residue analysis of 2,4-D, dicamba and 4-CPA in food crops.

Quantifying Dicamba Volatility under Field Conditions: Part I, Methodology.

Quantitative assessment of the volatility of field applied herbicides requires orchestrated sampling logistics, robust analytical methods, and sophisticated modeling techniques. This manuscript describes a comprehensive system developed to measure dicamba volatility in an agricultural setting. Details about study design, sample collection, analytical chemistry, and flux modeling are described. A key component of the system is the interlaboratory validation of an analytical method for trace level detection (limit of quantitation of 1.0 ng/PUF) of dicamba in polyurethane foam (PUF) air samplers. Validation of field sampling and flux methodologies was conducted in a field trial that demonstrated agreement between predicted and directly measured dicamba air concentrations at a series of off-target locations. This validated system was applied to a field case study on two plots to demonstrate the utility of these methods under typical agricultural conditions. This case study resulted in a time-varying volatile flux profile, which showed that less than 0.2 ± 0.05% of the applied dicamba was volatilized over the 3-day sampling period.

Quantifying Dicamba Volatility under Field Conditions: Part II, Comparative Analysis of 23 Dicamba Volatility Field Trials.

This study summarizes 23 field trials (over six geographic locations, with each trial composed of a separate field site and an application event) for quantifying the postapplication volatilization of dicamba from fields treated with an array of dicamba-containing formulations and tank adjuvants at an application rate of 0.56 or 1.12 kg dicamba acid equivalents (a.e.) per hectare (0.5 or 1.0 lb dicamba a.e. per acre). The data span 3 years of testing over a range of locations, field types, and environmental conditions. The aerodynamic and the integrated horizontal flux methodologies were employed (and then averaged) for estimating the vertical flux from the field for periods extending to approximately 72 h post application. In all cases, the vertical flux peaked within 24 h of application and then decayed to much lower levels by day 3. Total volatile losses among all formulations and conditions ranged from 0.023 ± 0.003 to 0.302 ± 0.045% of the applied dicamba (median = 0.08%). Analysis of the recorded meteorological and soil conditions for each field trial failed to identify any single soil or weather parameter as a dominant driver of total volatile losses. Air concentrations of dicamba observed in the course of these trials were all below the no observed adverse effect concentration for conventional soybean plant height or yield, indicating that air concentrations directly above or outside of the dicamba-treated area would not cause a reduction in plant height or yield of conventional soybean.

Operative modalities and exposure to pesticides during open field treatments among a group of agricultural subcontractors.

This paper reports the results of a field study of occupational pesticide exposure (respiratory and dermal) among a group of Italian agricultural subcontractors. These workers consistently use pesticides during much of the year, thus resulting in a high exposure risk. Ten complete treatments were monitored during spring/summer. Pesticides that were applied included azinphos-methyl, dicamba, dimethoate, terbuthylazine, and alachlor. Several observations were made on worker operative modalities and the use of personal protective equipment (PPE) during work. Total potential and actual exposure ranged from 14 to 5700 microg and from 0.04 to 4600 microg, respectively. Dermal exposure contributed substantially more than inhalation to the total exposure (93.9-100%). Hand contamination ranged from 0.04 to 4600 microg and was the major contributor to dermal exposure. Penetration through specific protective garments was less than 2.4% in all cases, although penetration through general work clothing was as high as 26.8%. The risk evaluation, based on comparison between acceptable daily intake and total absorbed doses, demonstrates that it is presumable to expect possible health effects for workers regularly operating without PPE and improper tractors. Comparisons between exposure levels and operative modalities highlighted that complete PPE and properly equipped tractors contributed to a significant reduction in total exposure to pesticides during agricultural activities. In conclusion, monitored agricultural subcontractors presented very different levels of pesticide exposure due to the high variability of operative modalities and use of PPE. These results indicate the need to critically evaluate the efficacy of training programs required for obtaining a pesticide license in Italy.

Synthesis of biomass tar-derived foams through spontaneous foaming for ultra-efficient herbicide removal from aqueous solution.

Pyrolysis is one of the most important approaches to convert waste biomass into renewable energy and biomaterials, and the tar is the inevitable by-product of this process. In this study, carbon foams were prepared innovatively with biomass tar as the precursor through spontaneous gas foaming approach and used for dicamba removal from aqueous solution. The results showed that prepared carbon foams had unique properties including rich microporous structure and high specific surface area (reaching 1667 m2/g). In addition, the prepared carbons had high thermal stability due to the high graphitic degree. The adsorption results indicated that pH showed a great effect on the adsorption of dicamba onto the prepared carbon foams. The carbon foam exhibited ultra-fast dicamba removal and ultra-high adsorption capacity of 891.74 mg/g at room temperature. The adsorption process was well described by pseudo-second-order kinetics and Langmuir isotherm models. The thermodynamic study indicated dicamba adsorption onto the prepared carbon foams was a spontaneous and exothermic process. In addition, the good reusability from recovery test demonstrated that the prepared carbon foams had promising potential for dicamba removal from aqueous solution.

Redox-Based Synthetic Biology Enables Electrochemical Detection of the Herbicides Dicamba and Roundup via Rewired Escherichia coli.

Synthetic biology is typically exploited to endow bacterial cells with new biosynthetic capabilities. It can also serve to create "smart" bacteria such as probiotics that detect and treat disease. Here, we show how minimally rewiring the genetic regulation of bacterial cells can enable their ability to recognize and report on chemical herbicides, including those routinely used to clear weeds from gardens and crops. In so doing, we demonstrate how constructs of synthetic biology, in this case redox-based synthetic biology, can serve as a vector for information flow mediating molecular communication between biochemical systems and microelectronics. We coupled the common genetic reporter, ß-galactosidase, with the E. coli superoxide response regulon promoter pSoxS, for detection of the herbicides dicamba and Roundup. Both herbicides activated our genetic construct in a concentration dependent manner. Results indicate robust detection using spectrophotometry, via the Miller assay, and electrochemistry using the enzymatic cleavage of 4-aminophenyl ß-d-galactopyranoside into the redox active molecule p-aminophenol. We found that environmental components, in particular, the availability of glucose, are important factors for the cellular detection of dicamba. Importantly, both herbicides were detected at concentrations relevant for aquatic toxicity.

Acidic herbicides in surface waters of Lower Fraser Valley, British Columbia, Canada.

In the period 2003-2005 a study was conducted to determine the occurrence, spatial and temporal distribution of five acidic herbicides in the Lower Fraser Valley (LFV) region of British Columbia, Canada. A high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) method capable of detecting analytes at the sub ng/L level was developed for this study. Samples were collected and analyzed from two references, five agricultural, two urban and five agricultural and urban mixed sites. Only (4-chloro-2-methylphenoxy)acetic acid and triclopyr were detected at the reference sites. The highest concentration of herbicide detected at the reference sites was 0.109ng/L for (4-chloro-2-methylphenoxy)acetic acid. Varying levels of all of the herbicides monitored were detected at the urban, agricultural and the mixed sites. For the urban sites the highest concentration of herbicide detected was 66.6ng/L for 2-(4-chloro-2-methylphenoxy)propanoic acid. For the agricultural sites the highest concentration of herbicide detected was 345ng/L for (2,4-dichlorophenoxy)acetic acid (2,4-D). For the mixed sites the highest concentration of herbicide detected was 1230ng/L for 2,4-D. Overall the mixed sites showed highest concentrations and detection frequencies followed by the agricultural and urban sites. With few exceptions higher concentrations of herbicides were observed for samples collected during spring than for samples collected during fall. The detected concentrations of herbicides were evaluated against established water quality criteria. Herbicide data presented in this study provide reference levels for future pesticide monitoring programs in the region.

Dacthal and chlorophenoxy herbicides and chlorothalonil fungicide in eggs of osprey (Pandion haliaetus) from the Duwamish-Lake Washington-Puget Sound area of Washington state, USA.

Current-use chlorophenoxy herbicides including 2,4-dichlorophenoxyacetic acid, dicamba, triclopyr, dicamba, dimethyl tetrachloroterephthalate (DCPA or dacthal), and the metabolite of pyrethroids, 3-phenoxybenzoic acid (3-PBA), and the fungicide, chlorothalonil, were investigated in the eggs of osprey (Pandion haliaetus) that were collected from 15 sites from five study areas Puget Sound/Seattle area of Washington State, USA. DCPA differs from acidic chlorophenoxy herbicides, and is not readily hydrolyzed to free acid or acid metabolites, and thus we developed a new method. Of the 12 chlorophenoxy herbicides and chlorothalonil analyzed only DCPA could be quantified at six of these sites (2.0 to 10.3 pg/g fresh weight). However, higher levels (6.9 to 85.5 pg/g fresh weight) of the unexpected DCPA structural isomer, dimethyl tetrachlorophthalate (diMe-TCP) were quantified in eggs from all sites. diMe-TCP concentrations tended to be higher in eggs from the Everett Harbor area. As diMe-TCP is not an industrial product, and not commercially available, the source of diMe-TCP is unclear. Regardless, these findings indicate that DCPA and diMe-TCP can be accumulated in the food chain of fish-eating osprey, and transferred in ovo to eggs, and thus may be of concern to the health of the developing chick and the general reproductive health of this osprey population.

Determination of chlorinated acid herbicides in vegetation and soil by liquid chromatography/electrospray-tandem mass spectrometry.

The method presented uses reversed-phase liquid chromatography with negative electrospray ionization and tandem mass spectrometry to analyze 9 chlorinated acid herbicides in soil and vegetation matrixes: clopyralid, dicamba, MCPP, MCPA, 2,4-DP, 2,4-D, triclopyr, 2,4-DB, and picloram. A 20 g portion is extracted with a basic solution and an aliquot acidified and micropartitioned with 3 mL chloroform. Vegetation samples are subjected to an additional cleanup with a mixed-mode anion exchange solid-phase extraction cartridge. Two precursor product ion transitions per analyte are measured and evaluated to provide the maximum degree of confidence in results. Average recoveries for 3 different soil types tested ranged from 72 to 107% for all compounds with the exception of 2,4-DB at 56-99%. Average recoveries for the 3 different vegetation types studied were lower and ranged from 53 to 80% for all compounds.

Isotope dilution high-resolution gas chromatography/high-resolution mass spectrometry method for analysis of selected acidic herbicides in surface water.

In this work, an isotope dilution method for determination of selected acidic herbicides by high-resolution gas chromatography/high-resolution mass spectrometry (HRGC/HRMS) was developed for surface water samples. Average percent recoveries of native analytes were observed to be between 70.8 and 93.5% and average recoveries of labeled quantification standards [(13)C(6)]2,4-D and [(13)C(6)]2,4,5-T were 85.5 and 101%, respectively. Using this method, detection limits of 0.05 ng/L for dicamba, MCPA, MCPP, and triclopyr, and 0.5 ng/L for 2,4-D were routinely achieved. The method was applied to measuring the concentration of these analytes in surface water samples collected from five sampling locations in the Lower Fraser Valley region of British Columbia, Canada. All of the herbicides monitored were detected at varying levels in the surface water samples collected. The highest concentrations detected for each analyte were 345 ng/L for 2,4-D, 317 ng/L for MCPA, 271 ng/L for MCPP, 15.7 ng/L for dicamba, and 2.18 ng/L for triclopyr. Average detection frequencies of the herbicides were 95% for MCPA, 80% for MCPP, 70% for dicamba, 65% for 2,4-D, and 46% for triclopyr. Seasonal variations of herbicide levels are also discussed.

Quantitative analysis of dicamba residues in raw agricultural commodities with the use of ion-pairing reagents in LC-ESI-MS/MS.

A sensitive and selective HPLC-MS/MS method was developed for the quantitative analysis of dicamba residues in raw agricultural commodities (RACs). Instead of analysis in the traditionally used negative electrospray ionization (ESI) mode, these anionic compounds were detected in positive ESI with the use of ion-pairing reagents. In this approach, only a small amount (60µM) of a commercially available dicationic ion-pairing reagent was introduced into the post-column sample stream. This method has been validated in six different types of RACs including corn grain, corn stover, cotton seed, soybean, soy forage and orange with satisfactory quantitative accuracy and precision. The limits of quantitation (LOQ) values for these analytes were 1.0 to 3.0µg/kg. The standard curves were linear over the range of the tested concentrations (3.0 to 500µg/kg), with correlation coefficient (r) values≥0.999. Evaluation of ionization effects in RAC matrix extracts using diluent blanks for comparison showed no significant matrix effects were present.

Development of models to predict dose of pesticides in professional turf applicators.

Epidemiologic studies designed to assess the chronic effects of pesticides are limited by inadequate measurements of exposures. Although cohort studies have been initiated to evaluate the effects of 2,4-dichlorophenoxyacetic acid (2,4-D) and other pesticides in professional turf applicators, they may have limited power to detect significant health risks and may be subject to bias from exposure measurement error. In this study, the doses of 2,4-D, mecoprop [2-(4-chloro-2 methylphenoxy) propionic acid, MCPP] and dicamba (3,6-dichloro-o-anisic acid) were evaluated in a group of 98 professional turf applicators from 20 companies across southwestern Ontario. During a 1-week period (Saturday to Thursday), the volume of pesticide (active ingredient) applied was only weakly related to the total dose of 2,4-D absorbed (R(2)=0.21). Two additional factors explained a large proportion of variation in dose: the type of spray nozzle used and the use of gloves while spraying. Individuals who used a fan-type nozzle had significantly higher doses than those who used a gun-type nozzle. Glove use was associated with significantly lower doses. Job satisfaction and current smoking influenced the dose but were not highly predictive. In the final multiple regression models predicting total absorbed dose of 2,4-D and mecoprop, approximately 63-68% of the variation was explained. The future application of these models for epidemiologic research will depend on the availability of information and records from employers, the feasibility of contacting study subjects and cost.

Development of an enzyme-linked immunosorbent assay for the detection of dicamba.

A competitive indirect enzyme-linked immunosorbent assay (CI-ELISA) was developed to quantitate the herbicide dicamba (3,6-dichloro-2-methoxybenzoic acid) in water. The CI-ELISA has a detection limit of 2.3 microg L(-1) and a linear working range of 10--10000 microg L(-1) with an IC(50) value of 195 microg L(-1). The dicamba polyclonal antisera did not cross-react with a number of other herbicides tested but did cross-react with a dicamba metabolite, 5-hydroxydicamba, and structurally related chlorobenzoic acids. The assay was used to estimate quantitatively dicamba concentrations in water samples. Water samples were analyzed directly, and no sample preparation was required. To improve detection limits, a C(18) (reversed phase) column concentration step was devised prior to analysis, and the detection limits were increased by at least by 10-fold. After the sample preconcentration, the detection limit, IC(50), and linear working range were 0.23, 19.5, and 5-200 microg L(-1), respectively. The CI-ELISA estimations in water correlated well with those from gas chromatography-mass spectrometry (GC-MS) analysis (r(2) = 0.9991). This assay contributes to reducing laboratory costs associated with the conventional GC-MS residue analysis techniques for the quantitation of dicamba in water.

Biodegradability of Atrazine, Cyanazine and Dicamba under methanogenic condition in three soils of China.

Persistence and degradation of the herbicides Atrazine, Cyanazine and Dicamba were measured in laboratory microcosms incubated under methanogenic condition using three soils of China. Results showed that Atrazine was more resistant to degradation than Cyanazine and Dicamba for the 300 days of incubation. Between 30% and 40% of the initially introduced chemicals were found to be not recoverable through solvent extraction of the incubated soils. Our results also indicated that the half-life of these herbicides in the three soils generally followed: Atrazine>Cyanazine>Dicamba. Biodegradation of Cyanazine and Dicamba was further substantiated by establishing enrichment cultures in which the degradation of the respective herbicides could be accelerated by the microorganisms. Our results suggest that biodegradation of xenobiotics can be established through enrichment culture transfer technique and non-extractability of chemicals should be taken into account in evaluation of chemicals' fate and risk.

Quantifying vapor drift of dicamba herbicides applied to soybean.

Recent advances in biotechnology have produced cultivars of corn, soybean, and cotton resistant to the synthetic-auxin herbicide dicamba. This technology will allow dicamba herbicides to be applied in new crops, at new periods in the growing season, and over greatly expanded areas, including postemergence applications in soybean. From past and current use in corn and small grains, dicamba vapor drift and subsequent crop injury to sensitive broadleaf crops has been a frequent problem. In the present study, the authors measured dicamba vapor drift in the field from postemergence applications to soybean using greenhouse-grown soybean as a bioassay system. They found that when the volatile dimethylamine formulation is applied, vapor drift could be detected at mean concentrations of 0.56 g acid equivalent dicamba/ha (0.1% of the applied rate) at 21 m away from a treated 18.3 × 18.3 m plot. Applying the diglycolamine formulation of dicamba reduced vapor drift by 94.0%. With the dimethylamine formulation, the extent and severity of vapor drift was significantly correlated with air temperature, indicating elevated risks if dimethylamine dicamba is applied early to midsummer in many growing regions. Additional research is needed to more fully understand the effects of vapor drift exposures to nontarget crops and wild plants.