Understanding the risk of using herbicides for tree root removal into wastewater treatment plant performance.

Adding herbicides to sewer lines, a common practice for controlling root intrusion in sewer pipes, may adversely impact downstream wastewater treatment by inhibiting nitrification and denitrification performance. This study investigated the effects of herbicides, namely diquat, triclopyr, and 2-methyl-4-chlorophenoxyacetic acid (MCPA)-dicamba, on these processes. Various parameters were monitored, including oxygen uptake rate (OUR), nutrients (NH3-N, TP, NO3-N, and NO2-N), chemical oxygen demand (COD), and herbicide concentrations. It was found that nitrification was not affected by OUR in the presence of each herbicide at various concentrations (1, 10, and 100 mg L-1). Additionally, MCPA-dicamba at various concentrations demonstrated minimal inhibition in the nitrification process compared to diquat and triclopyr. COD consumption was not affected by the presence of these herbicides. However, triclopyr significantly inhibited NO3-N formation in the denitrification process at various concentrations. Similar to nitrification process, both COD consumption and herbicide reduction concentration were not affected by the presence of herbicides during the denitrification process. Adenosine triphosphate measurements showed minimal impact on nitrification and denitrification processes when herbicides were present in the solution up to a concentration of 10 mg L-1. Tree root kill efficiency experiments were performed on Acacia melanoxylon. Considering the performance on nitrification and denitrification process, diquat emerged as the best herbicide option (concentration of 10 mg L-1), with a 91.24% root kill efficiency.

Environmental-friendly hydrochar-montmorillonite composite for efficient catalytic degradation of dicamba and alleviating its damage to crops.

In recent years, carbon-based materials catalyzing peroxymonosulfate (PMS) for green degradation of persistent organic pollutants have attracted increasing attention. However, PMS activation by hydrochar composite (e.g. hydrochar-montomorillonite) has rarely been investigated. Herein, a simple preparation, low-cost and eco-friendly catalyst of hydrochar-montmorillonite composite (HC-Mt) was prepared to firstly catalyze PMS for the degradation of dicamba (DIC). The as-prepared HC-Mt showed a remarkably better catalyzing performance for PMS than pure hydrochar (HC) due to its good physicochemical characteristics and abundant oxygen-containing groups. Furthermore, the electron spin resonance (ESR) and quenching tests revealed that active species such as SO4-, OH and O2- all participated in the degradation process. DIC sites on C6, Cl 10, and O15 exhibited higher reactivity according to the density functional theory (DFT) calculation, which were easily attacked by active species. The DIC degradation mainly occurred via hydroxyl substitution, decarboxylation, oxidation and ring-cleavage and finally most of the intermediates were mineralized into CO2 and H2O. Finally, the phytotoxicity assessment was measured by the germination growth situation of tobacco and mung beans in the presence of DIC (with or without treatment by HC-Mt/PMS). The result showed that HC-Mt/PMS could significantly reduce the phytotoxicity of DIC to crops, suggesting that catalyzing PMS using HC-Mt was environmentally friendly. Therefore, this work did not only provide a novel catalyzing PMS strategy using hydrochar composite for wastewater treatment, but also give a new idea for herbicide phytotoxicity management.

Inheritance of dicamba-resistance in allotetraploid Chenopodium album.

BACKGROUND: Chenopodium album L. is a troublesome weed in spring-planted crops, and different levels of ploidy have been documented for this weed species. A population of C. album has evolved resistance to dicamba. The level of ploidy and inheritance of dicamba resistance was studied in this population. RESULTS: The resistant and susceptible individuals of C. album were confirmed as tetraploid by flow cytometry. Pair-crosses were made between ten resistant and susceptible individuals. Eight F1 individuals from five crosses were confirmed resistant after treating with dicamba at 400 g a.e. ha-1 . These individuals were selfed, and the response of their progenies to dicamba was assessed in dose-response experiments, and the results confirmed the resistance trait was dominant. Furthermore, an analysis of the segregation patterns revealed that the segregation response of all F2 progenies fitted a 3:1 (resistant/susceptible) ratio when treated with dicamba at 200, 400 and 800 g a.e. ha-1 , suggesting a single gene was responsible for dicamba resistance. CONCLUSIONS: Dicamba resistance in the studied tetraploid population of C. album is governed by a single dominant gene. This type of inheritance suggests that selection for dicamba resistance can occur readily. © 2022 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Levels of pesticides and trace metals in water, sediment, and fish of a large, agriculturally-dominated river.

Basin land-use interacts with hydrology to deliver chemical contaminants to riverine environments. These chemicals are eventually taken up by aquatic organisms, where they can cause harmful effects. However, knowledge gaps related to the connections between hydrological, chemical, and biological processes currently limit our ability to forecast potential future changes in contaminant concentrations accurately. In this study, concentrations of three pesticide classes (organochlorines, organophosphates, and herbicides) and a standard suite of trace metals were analyzed in the South Saskatchewan River, Canada in 2020 and 2021 in water, sediments, and fishes. Organochlorine pesticides have been banned in Canada since the 1970s, yet there were some detections for methoxychlor and lindane, predominantly in sediment and fish samples, which could be attributed to legacy contamination. Except for malathion and parathion, organophosphate pesticides were scarcely detected in both sampling years in all matrices, and neonicotinoids were below detection in all samples. Conversely, the herbicides 2,4-D and dicamba were detected consistently throughout all locations in water samples for both sampling years. Overall, concentrations were 3 times higher in 2020 when river discharge was ∼2 times higher, suggesting run-off from the surrounding catchment or disturbance of contaminated sediments. Analysis for trace metals revealed that Cu and Zn exceeded sediment quality guidelines in some locations. Mercury concentrations exceeded the guidelines for about 18% of the samples (water and sediment) analyzed. These findings fill gaps in monitoring datasets and highlight key links between hydrology and chemistry that can be further explored in computational models to predict future contaminant trends in freshwater systems.

Toward revealing the role of the cation in the phytotoxicity of the betaine-based esterquats comprising dicamba herbicide.

In this study, two homologous series of esterquats comprising alkyl (from ethyl to octadecyl) betainate cations and bromide as well as dicamba anions were successfully synthesized, starting from a renewable raw material - glycine betaine. Due to the favorable octanol-water partition coefficient and utilization of biodegradable cations of natural origin, synthesized esterquats can be considered promising alternatives to currently applied dicamba-based formulations. In addition, the obtained results allowed us to verify whether the organic cations in quaternary ammonium salts containing herbicidally active anions (such as dicamba) play the role of biologically inactive adjuvants that only enhance the efficiency of the active ingredient or if they simultaneously exhibit a significant degree of phytotoxicity. Analysis of the influence of alkyl betainate esterquats containing nonherbicidal (bromide) anions on seedlings of white mustard revealed that alkyl betainate cations promote the germination of white mustard seeds; however, the subsequent growth of the seedlings was significantly inhibited. Further studies performed on white mustard and cornflower plants in a stage of 4-6 leaves allowed us to conclude that in the case of sensitive plants, the high phytotoxicity can be attributed to the presence of the dicamba anion, whereas for more resistant plants the additional influence of the cation on the phytotoxic effect is visible. Esterquats comprising a dodecyl substituent or longer had high surface active properties. Nonetheless, their contact angle values were not correlated with phytotoxicity data, indicating an additional influence of the cation on this stage of plant development. Interestingly, subsequent dose-response experiments conducted for two selected dicamba-based products confirmed that the greatest phytotoxicity was expressed by compounds containing a decyl substituent.

Genotoxicity evaluation of 2,4-D, dicamba and glyphosate alone or in combination with cell reporter assays for DNA damage, oxidative stress and unfolded protein response.

The current generation of carcinogenicity tests is often insufficient to predict cancer outcomes from pesticide exposures. In order to facilitate health risk assessment, The International Agency for Research on Cancer identified 10 key characteristics which are commonly exhibited by human carcinogens. The ToxTracker panel of six validated GFP-based mouse embryonic stem reporter cell lines is designed to measure a number of these carcinogenic properties namely DNA damage, oxidative stress and the unfolded protein response. Here we present an evaluation of the carcinogenic potential of the herbicides glyphosate, 2,4-D and dicamba either alone or in combination, using the ToxTracker assay system. The pesticide 2,4-D was found to be a strong inducer of oxidative stress and an unfolded protein response. Dicamba induced a mild oxidative stress response, whilst glyphosate did not elicit a positive outcome in any of the assays. The results from a mixture of the three herbicides was primarily an oxidative stress response, which was most likely due to 2,4-D with dicamba or glyphosate only playing a minor role. These findings provide initial information regarding the risk assessment of carcinogenic effects arising from exposure to a mixture of these herbicides.

Dicamba elevates concentrations of S-adenosyl methionine but does not induce oxidative stress or alter DNA methylation in rainbow trout (Oncorhynchus mykiss) hepatocytes.

Dicamba is a benzoic acid herbicide used to target woody and broadleaf weeds in industrial, domestic, and municipal spheres. Because of its widespread use, dicamba is frequently detected in surface waters near sites of application. However, little is known regarding the effects of dicamba on freshwater fishes. In the present study, primary cultures of hepatocytes from rainbow trout (Oncorhynchus mykiss) were exposed to either an environmentally relevant (0.22 or 2.2 µg L-1) or supra-environmental (22 µg L-1) concentration of dicamba for 48 h to investigate if oxidative stress is a mechanism of toxicity. mRNA abundances of genes involved in the response to oxidative stress, levels of lipid peroxidation, and concentrations of glutathione and s-adenosyl methionine (SAM) were quantified. Results indicate that dicamba does not induce oxidative stress. However, exposure to 2.2 µg L-1 of dicamba did cause a 5.24-fold increase in concentrations of SAM. To investigate the mechanisms of increased SAM, effects of dicamba on global and genome-wide DNA methylation were quantified. Dicamba did not cause changes to DNA methylation. Overall, dicamba was not acutely toxic to hepatocytes and did not cause oxidative stress or changes in DNA methylation at environmentally relevant concentrations.

Dicamba use and cancer incidence in the agricultural health study: an updated analysis.

BACKGROUND: The herbicide dicamba has been commonly used agriculturally and residentially. Recent approval of genetically engineered dicamba-resistant crops is expected to lead to increased dicamba use, and there has been growing interest in potential human health effects. A prior analysis in the Agricultural Health Study (AHS) suggested associations between dicamba and colon and lung cancer. We re-evaluated dicamba use in the AHS, including an additional 12 years and 2702 exposed cancers. METHODS: The AHS is a prospective cohort of pesticide applicators in Iowa and North Carolina. At enrollment (1993-1997) and follow-up (1999-2005), participants reported dicamba use. Exposure was characterized by cumulative intensity-weighted lifetime days, including exposure lags of up to 20 years. We estimated relative risks (RR) and 95% confidence intervals (CI) using multivariable Poisson regression for incident cancers diagnosed from enrollment through 2014/2015. RESULTS: Among 49 922 applicators, 26 412 (52.9%) used dicamba. Compared with applicators reporting no dicamba use, those in the highest quartile of exposure had elevated risk of liver and intrahepatic bile duct cancer (nexposed = 28, RRQ4 = 1.80, CI: 1.26-2.56, Ptrend < 0.001) and chronic lymphocytic leukaemia (CLL, nexposed = 93, RRQ4 = 1.20, CI: 0.96-1.50, Ptrend = 0.01) and decreased risk of myeloid leukaemia (nexposed = 55, RRQ4 = 0.73, CI: 0.51-1.03, Ptrend = 0.01). The associations for liver cancer and myeloid leukaemia remained after lagging exposure of up to 20 years. CONCLUSIONS: With additional follow-up and exposure information, associations with lung and colon cancer were no longer apparent. In this first evaluation of liver and intrahepatic bile duct cancer, there was an association with increasing use of dicamba that persisted across lags of up to 20 years.

Simulated drift of dicamba and 2, 4-D on soybeans: effects of application dose and time / Deriva simulada de dicamba e 2, 4-D na soja: efeitos da dose de aplicação e tempo

The use of soybean varieties resistant to the herbicides dicamba and 2,4-D may lead to drifts towards areas grown with non-resistant varieties. The aim of this study was to evaluate the effects of dicamba and 2,4-D underdoses applied at the phenological stages V4 and R2 of soybeans. Two experiments were conducted with dicamba or 2,4-D in a randomized block design with four replications. The 4 × 2 + 1 factorial scheme was composed of four doses (0.028, 0.28, 2.8, and 28 g ae ha−1) of dicamba or 2,4-D applied at two phenological stages (V4 and R2) + a control treatment (without herbicide application). Dicamba underdoses caused damage to soybean crop affecting its vegetative growth and yield; the injuries caused by 2,4-D were neither enough to damage crop nor affect yield components. Dicamba underdoses applied at V4 caused injuries of up to 41%, while in R2 they reached 70%. Plant height decreased by up to 61% when treated with dicamba. Soybean yield was reduced by 29 and 76% when the simulated drift occurred at V4 and R2, respectively, and at a dose of 28 g ae ha−1 of dicamba. For the tested underdoses, only 2,4-D had no effect in soybean crop yield.

Com a inserção de variedades de soja resistentes aos herbicidas dicamba e 2,4-D os eventos de deriva destes herbicidas para áreas com variedades não resistentes será passível de ocorrência. Objetivou-se neste trabalho avaliar os efeitos de subdoses de dicamba e 2,4-D aplicados nos estádios fenológicos V4 e R2 da cultura da soja. Dois experimentos foram conduzidos com dicamba ou 2,4-D em delineamento experimental de blocos casualizados, com quatro repetições. Adotou-se o esquema fatorial de 4 x 2 + 1 composto por quatro doses (0,028, 0,28, 2,8 e 28 g ea ha-1) de dicamba ou de 2,4-D, aplicados em dois estádios fenológicos (V4 e R2) + um tratamento testemunha (sem aplicação de herbicida). As subdoses de dicamba provocaram danos na cultura da soja, afetando o desenvolvimento vegetativo e a produtividade, enquanto o 2,4-D não provocou injúrias suficientes para provocar danos que comprometessem a cultura, e desta forma, não afetou os componentes de produção. As subdoses de dicamba aplicadas no estádio V4 provocou injúrias de até 41%, enquanto em R2 chegaram a 70%. A altura das plantas reduziu em até 61% quando tratadas com dicamba. A produtividade da soja foi reduzida em 29 e 76%, quando a deriva simulada ocorreu nos estádios V4 e R2, respectivamente, e na dose de 28 g ea ha-1 de dicamba. Nas subdoses testadas somente o 2,4-D não afetou a produtividade da cultura da soja.

Auxinic herbicides induce oxidative stress on Cnesterodon decemmaculatus (Pisces: Poeciliidae).

Pesticides might increase the production of reactive oxygen species (ROS). Dicamba (DIC) and 2,4-dichlorophenoxyacetic acid (2,4-D) are auxinic herbicides commonly applied in agroecosystems to control unwanted weeds. We analysed the oxidative damage exerted on the fish Cnesterodon decemmaculatus by an acute exposure to DIC- and 2,4-D-based herbicides formulations Banvel® and DMA®, respectively. The Endo III- and Fpg-modified alkaline comet assay was employed for detecting DNA damage caused by oxidative stress, whereas enzymatic and non-enzymatic biomarkers such as the activities of catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and glutathione content (GSH) were used to assess antioxidant response to these two herbicides. At the DNA level, results demonstrate that both auxinic herbicides induce oxidative damage at purines level. An increase on CAT and GST activities were detected in 48 h- and 96 h-treated specimens with both auxinics. GSH content decreased in fish exposed to DIC during 48 h and to 2,4-D after 96 h of exposure. Additionally, a diminished AChE activity in specimens treated with DIC and 2,4-D was observed only after 96 h. Total protein content decreased in fish exposed to both auxinics during 96 h. These results represent the first evaluation of oxidative damage related to DIC and 2,4-D exposure on a fish species as the Neotropical freshwater teleost C. decemmaculatus.

Roles of Two Glutathione-Dependent 3,6-Dichlorogentisate Dehalogenases in Rhizorhabdus dicambivorans Ndbn-20 in the Catabolism of the Herbicide Dicamba.

The herbicide dicamba is initially demethylated to 3,6-dichlorosalicylate (3,6-DCSA) in Rhizorhabdus dicambivorans Ndbn-20 and is subsequently 5-hydroxylated to 3,6-dichlorogentisate (3,6-DCGA). In the present study, two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, were identified in strain Ndbn-20. DsmH2 shared a low identity (only 31%) with the tetrachlorohydroquinone (TCHQ) dehalogenase PcpC from Sphingobium chlorophenolicum ATCC 39723, while DsmH1 shared a high identity (79%) with PcpC. In the phylogenetic tree of related glutathione S-transferases (GSTs), DsmH1 and DsmH2, together with PcpC and the 2,5-dichlorohydroquinone dehalogenase LinD, formed a separate clade. DsmH1 and DsmH2 were synthesized in Escherichia coli BL21 and purified as His-tagged enzymes. Both enzymes required glutathione (GSH) as a cofactor and could 6-dechlorinate 3,6-DCGA to 3-chlorogentisate in vitro DsmH2 had a significantly higher catalytic efficiency toward 3,6-DCGA than DsmH1. Transcription and disruption analysis revealed that DsmH2 but not DsmH1 was responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20 in vivo Furthermore, we propose a novel eta class of GSTs to accommodate the four bacterial dehalogenases PcpC, LinD, DsmH1, and DsmH2.IMPORTANCE Dicamba is an important herbicide, and its use and leakage into the environment have dramatically increased since the large-scale planting of genetically modified (GM) dicamba-resistant crops in 2015. However, the complete catabolic pathway of dicamba has remained unknown, which limits ecotoxicological studies of this herbicide. Our previous study revealed that 3,6-DCGA was an intermediate of dicamba degradation in strain Ndbn-20. In this study, we identified two glutathione-dependent 3,6-DCGA dehalogenases, DsmH1 and DsmH2, and demonstrated that DsmH2 is physiologically responsible for the 6-dechlorination of 3,6-DCGA in strain Ndbn-20. GSTs play an important role in the detoxification and degradation of a variety of endogenous and exogenous toxic compounds. On the basis of their sequence identities, phylogenetic status, and functions, the four bacterial GSH-dependent dehalogenases (PcpC, LinD, DsmH1, and DsmH2) were reclassified as a new eta class of GSTs. This study helps us to elucidate the microbial catabolism of dicamba and enhances our understanding of the diversity and functions of GSTs.

Rhizorhabdus dicambivorans sp. nov., a dicamba-degrading bacterium isolated from compost.

Strain Ndbn-20T, a Gram-staining-negative, non-spore-forming bacterium, was isolated from compost of plant litter. The strain was able to degrade dicamba. Phylogenetic analysis based on 16S rRNA gene sequences indicated that Ndbn-20Trepresented a member of the family Sphingomonadaceae of the Alphaproteobacteria and showed high sequence similarities to Rhizorhabdusargentea SP1T (98.8 %), Sphingomonaswittichii RW1T (97.9 %), Sphingomonasstarnbergensis 382T (97.7 %) and Sphingomonashistidinilytica UM2T (97.7 %). However, the strain showed low DNA sequence relatedness with R. argentea SP1T (45.6±1.9 %), S. wittichii RW1T (33.5±2.3 %), S.histidinilytica UM2T (39.4±3.6 %) and S. starnbergensis382T (42.1±4.1 %). Ndbn-20T possessed Q-10 as the predominant ubiquinone, spermidine as the major polyamine, and summed feature 8 (comprising C18 : 1ω7c/C18 : 1ω6c), summed feature 3 (comprising C16 : 1ω7c/C16 : 1ω6c), C17 : 1ω6c, C16 : 0 and C14 : 02-OH as the major fatty acids (>5 % of the total). The profile of polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, glycolipid, sphingoglycolipid, phosphatidyldimethylethanolamine and phosphatidylglycerol. The DNA G+C content was 65.4 mol%. Based on a polyphasic taxonomic analysis, strain Ndbn-20T is proposed to represent a novel species of the genus Rhizorhabdus, with the proposed name of Rhizorhabdus dicambivorans sp. nov. The type strain is Ndbn-20T (=CCTCC AB 2016143=KACC 18661).

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.

O-Demethylations catalyzed by Rieske nonheme iron monooxygenases involve the difficult oxidation of a saturated C-H bond.

Dicamba monooxygenase (DMO) catalyzes the O-demethylation of dicamba (3,6-dichloro-2-methoxybenzoate) to produce 3,6-dichlorosalicylate and formaldehyde. Recent crystallographic studies suggest that DMO catalyzes the challenging oxidation of a saturated C-H bond within the methyl group of dicamba to form a hemiacetal intermediate. Testing of this hypothesis was made possible by our development of two new independent techniques. As a novel method to allow use of (18)O2 to follow reaction products, bisulfite was used to trap newly formed (18)O-formaldehyde in the stable adduct, hydroxymethanesulfonate (HMS(-)), and thereby prevent the rapid exchange of (18)O in formaldehyde with (16)O in water. The second technique utilized unique properties of Pseudomonas putida formaldehyde dehydrogenase that allow rapid conversion of (18)O-formaldehyde into stable and easily detectable (18)O-formic acid. Experiments using these two new techniques provided compelling evidence for DMO-catalyzed oxidation of the methyl group of dicamba, thus validating a mechanism for DMO [and for vanillate monooxygenase, a related Rieske nonheme iron monooxygenase] that involves the difficult oxidation of a saturated C-H bond.

Solid-phase synthesis and DNA binding studies of dichloroplatinum(ii) conjugates of dicarba analogues of octreotide as new anticancer drugs.

The first dichloroplatinum(ii) conjugates of dicarba analogues of octreotide, which is expected to act as a 'tumour-targeting device', have been efficiently synthesized following a stepwise solid-phase approach; these compounds emulate the mechanism of cisplatin since they form a 1,2-intrastrand cross-link with two consecutive guanines of an oligonucleotide.

Physicochemical study of the sorption of pesticides by wood components.

The sorption-desorption and interaction mechanisms of three non-ionic (linuron, alachlor, and metalaxyl) and two ionic (paraquat and dicamba) pesticides by three commercial lignins (hydrophobic macromolecule) and cellulose (hydrophilic macromolecule) as wood components were studied. Wood is a low-cost and environmentally friendly material proposed in recent years to immobilize pesticides in soils. The influence of sorbent and pesticide properties and the identification of the functional groups of the organic molecules involved in sorption were evaluated by a statistical approach and by Fourier transform infrared spectroscopy. The sorption isotherms of non-ionic pesticides by the lignins and cellulose fit the Freundlich model, and those of the ionic pesticides also fit the Langmuir model. The sorption constants of pesticides by cellulose were 62-, 9-, 24-, 119-, and 3-fold lower than those for the sorption by lignins. A predictive model of pesticide sorption indicated that 88.5% of the variability in the sorption coefficient normalized to the organic carbon content could be explained in terms of the variability of the polarity index and the octanol-water partition coefficient of sorbent and sorbate. The greater irreversibility observed for ionic pesticides was attributed to the involvement of simultaneous interaction mechanisms. The results obtained contribute the knowledge of sorption capacity of pesticides by lignin/cellulose, the main components of woods and ubiquitous materials in the environment.

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.

Characterization of Paracoccidioides brasiliensis PbDfg5p, a cell-wall protein implicated in filamentous growth.

The dimorphic fungus Paracoccidioides brasiliensis is the causative agent of the most frequent systemic mycosis in Latin America. In humans, infection starts by inhalation of fungal propagules, which reach the pulmonary epithelium and differentiate into the yeast parasitic phase. Here we describe the characterization of a Dfg5p (defective for filamentous growth) homologue of P. brasiliensis, a predictable cell wall protein, first identified in Saccharomyces cerevisiae. The protein, the cDNA and genomic sequences were analysed. The cloned cDNA was expressed in Escherichia coli and the purified rPbDfg5p was used to obtain polyclonal antibodies. Immunoelectron microscopy and biochemical studies demonstrated the presence of PbDfg5p in the fungal cell wall. Enzymatic treatments identified PbDfg5p as a beta-glucan linked protein that undergoes N-glycosylation. The rPbDfg5p bound to extracellular matrix components, indicating that those interactions could be important for initial steps leading to P. brasiliensis attachment and colonization of host tissues.

Dicamba resistance: enlarging and preserving biotechnology-based weed management strategies.

The advent of biotechnology-derived, herbicide-resistant crops has revolutionized farming practices in many countries. Facile, highly effective, environmentally sound, and profitable weed control methods have been rapidly adopted by crop producers who value the benefits associated with biotechnology-derived weed management traits. But a rapid rise in the populations of several troublesome weeds that are tolerant or resistant to herbicides currently used in conjunction with herbicide-resistant crops may signify that the useful lifetime of these economically important weed management traits will be cut short. We describe the development of soybean and other broadleaf plant species resistant to dicamba, a widely used, inexpensive, and environmentally safe herbicide. The dicamba resistance technology will augment current herbicide resistance technologies and extend their effective lifetime. Attributes of both nuclear- and chloroplast-encoded dicamba resistance genes that affect the potency and expected durability of the herbicide resistance trait are examined.

Cancer incidence among pesticide applicators exposed to dicamba in the agricultural health study.

BACKGROUND: Dicamba is an herbicide commonly applied to crops in the United States and abroad. We evaluated cancer incidence among pesticide applicators exposed to dicamba in the Agricultural Health Study, a prospective cohort of licensed pesticide applicators in North Carolina and Iowa. METHODS: Detailed pesticide exposure information was obtained through a self-administered questionnaire completed from 1993 to 1997. Cancer incidence was followed through 31 December 2002 by linkage to state cancer registries. We used Poisson regression to estimate rate ratios and 95% confidence intervals for cancer subtypes by tertiles of dicamba exposure. Two dicamba exposure metrics were used: lifetime exposure days and intensity-weighted lifetime exposure days (lifetime days x intensity score). RESULTS: A total of 41,969 applicators were included in the analysis, and 22,036 (52.5%) reported ever using dicamba. Exposure was not associated with overall cancer incidence nor were there strong associations with any specific type of cancer. When the reference group comprised low-exposed applicators, we observed a positive trend in risk between lifetime exposure days and lung cancer (p = 0.02), but none of the individual point estimates was significantly elevated. We also observed significant trends of increasing risk for colon cancer for both lifetime exposure days and intensity-weighted lifetime days, although these results are largely due to elevated risk at the highest exposure level. There was no apparent risk for non-Hodgkin lymphoma. CONCLUSIONS: Although associations between exposure and lung and colon cancer were observed, we did not find clear evidence for an association between dicamba exposure and cancer risk.