Phenoxyacetic Acid Herbicides Research Articles

Phenoxyacetic Acid Herbicide Exposure for Women on Ontario Farms

Women living and working on farms would be expected to have higher exposure to pesticides than the general nonoccupationally exposed population. Urinary concentrations of the herbicides 2,4-dichlorophenoxyacetic acid (2,4-D) and (4-chloro-2-methyl) phenoxyacetic acid (MCPA) were measured in 125 women living on farms in Ontario where these herbicides had recently been used for the first time that growing season. The women collected a spot urine void prior to the start of herbicide handling by spouses, followed by 2 consecutive 24-h urine samples. The pesticide applicator provided questionnaire data on pesticides that were used on the farm. Approximately 80% of the women had no detectable level of either herbicide in their urine. Geometric mean urinary concentrations of 2,4-D and MCPA in the d-2 samples were 0.7 µg/L. The responses to the questions on herbicide use on the farm were compared with urinary levels of the herbicide and the sensitivity for MCPA was determined to be 95–100%; however, the false positive rate for exposure was 70%. For 2,4-D, the sensitivity and specificity were approximately 70%, with a false positive rate of 30%. A simple question on whether the herbicide was used recently can accurately identify people who are likely not exposed; however, further research is required to be able to more validly predict those individuals who are exposed. Based on our study, it was concluded that exposure estimates based on questionnaire data alone may be fraught with uncertainties, which may differ depending on the particular pesticide of interest. This work does not necessarily reflect the views of Health Canada and no official endorsement should be inferred.

Antibody based methods for environmental and food analysis: a review

Antibodies have widely been used as analytical tools in various assays and techniques developed for clinical chemistry and endocrinology and for food and environmental research and risk control. Antibody development in the Veterinary Research Institute, Brno, and their application in ELISA and related techniques such as immunosensors has been directed especially to phenoxyacetic acid herbicides, s-triazine herbicides, sulfonylurea herbicides, polychlorinated biphenyls, surfactants (linear alkylbenzene sulphonates) and toxic metabolites (nonylphenol), and selected veterinary drugs (namely nitrofurans and sulfonamides). This paper provides an overview of progress achieved in the production of key immunoreagents in this laboratory (and in some cooperating laboratories)during the last 15 years. A comprehensive analysis of papers published on immunoassays and biosensors used in food and environmental research since 1980 demonstrates a rapid increase of publications on “ELISA and immunoassays” since 1991 (more than 500 papers were published each year since 1996). More than 200 papers on “biosensors” have been published each year since 2001. Atrazine was the most frequently found key word with ELISA and immunoassays: 438 papers were written by 971 authors from 308 institutions. The Web of Science® database is a useful tool for an assessment of the researcher’s and institution’s interest in the specific topics of research.

Comparative inter-species pharmacokinetics of phenoxyacetic acid herbicides and related organic acidsEvidence that the dog is not a relevant species for evaluation of human health risk

Phenoxyacetic acids including 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) are widely utilized organic acid herbicides that have undergone extensive toxicity and pharmacokinetic analyses. The dog is particularly susceptible to the toxicity of phenoxyacetic acids and related organic acids relative to other species. Active renal clearance mechanisms for organic acids are ubiquitous in mammalian species, and thus a likely mechanism responsible for the increased sensitivity of the dog to these agents is linked to a lower capacity to secrete organic acids from the kidney. Using published data describing the pharmacokinetics of phenoxyacetic and structurally related organic acids in a variety of species including humans, inter-species comparative pharmacokinetics were evaluated using allometic parameter scaling. For both 2,4-D and MCPA, the dog plasma half-life ( t 1/2 ) and renal clearance (Clr; mL/h) rates did not scale as a function of body weight across species; whereas for all other species evaluated, including humans, these pharmacokinetic parameters reasonably scaled. This exceptional response in the dog is clearly illustrated by comparing the plasma t 1/2 at comparable doses of 2,4-D and MCPA, across several species. At a dosage of 5 mg/kg, in dogs, the plasma t 1/2 for 2,4-D and MCPA were ∼92–106 and 63 h, respectively, which is substantially longer than in the rat (∼1 and 6 h, respectively) or in humans (12 and 11 h, respectively). This longer t 1/2 , and slower elimination in the dog, results in substantially higher body burdens of these organic acids, at comparable doses, relative to other species. Although these results indicate the important role of renal transport clearance mechanisms as determinants of the clearance and potential toxicity outcomes of phenoxyacetic acid herbicides across several species, other contributing mechanisms such as reabsorption from the renal tubules is highly likely. These findings suggest that for new structurally similar organic acids, a limited comparative species (rat versus dog) pharmacokinetic analysis early in the toxicology evaluation process may provide important insight into the relevance of the dog. In summary, the substantial difference between the pharmacokinetics of phenoxyacetic acids and related organic acids in dogs relative to other species, including humans, questions the relevance of using dog toxicity data for the extrapolation of human health risk.

Comparative inter-species pharmacokinetics of phenoxyacetic acid herbicides and related organic acidsEvidence that the dog is not a relevant species for evaluation of human health risk

Phenoxyacetic acids including 2,4-dichlorophenoxyacetic acid (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) are widely utilized organic acid herbicides that have undergone extensive toxicity and pharmacokinetic analyses. The dog is particularly susceptible to the toxicity of phenoxyacetic acids and related organic acids relative to other species. Active renal clearance mechanisms for organic acids are ubiquitous in mammalian species, and thus a likely mechanism responsible for the increased sensitivity of the dog to these agents is linked to a lower capacity to secrete organic acids from the kidney. Using published data describing the pharmacokinetics of phenoxyacetic and structurally related organic acids in a variety of species including humans, inter-species comparative pharmacokinetics were evaluated using allometic parameter scaling. For both 2,4-D and MCPA, the dog plasma half-life (t(1/2)) and renal clearance (Clr; mL/h) rates did not scale as a function of body weight across species; whereas for all other species evaluated, including humans, these pharmacokinetic parameters reasonably scaled. This exceptional response in the dog is clearly illustrated by comparing the plasma t(1/2) at comparable doses of 2,4-D and MCPA, across several species. At a dosage of 5mg/kg, in dogs, the plasma t(1/2) for 2,4-D and MCPA were approximately 92-106 and 63 h, respectively, which is substantially longer than in the rat (approximately 1 and 6 h, respectively) or in humans (12 and 11 h, respectively). This longer t(1/2), and slower elimination in the dog, results in substantially higher body burdens of these organic acids, at comparable doses, relative to other species. Although these results indicate the important role of renal transport clearance mechanisms as determinants of the clearance and potential toxicity outcomes of phenoxyacetic acid herbicides across several species, other contributing mechanisms such as reabsorption from the renal tubules is highly likely. These findings suggest that for new structurally similar organic acids, a limited comparative species (rat versus dog) pharmacokinetic analysis early in the toxicology evaluation process may provide important insight into the relevance of the dog. In summary, the substantial difference between the pharmacokinetics of phenoxyacetic acids and related organic acids in dogs relative to other species, including humans, questions the relevance of using dog toxicity data for the extrapolation of human health risk.

Adaptative responses in yeast to the herbicide 2-methyl-4-chlorophenoxyacetic acid at the level of intracellular pH homeostasis.

The objective of this work was to examine adaptative responses occurring in Saccharomyces cerevisiae following exposure to the herbicide 2-methyl-4-chlorophenoxyacetic acid (MCPA). The exposure of a yeast cell population to MCPA concentrations of moderate toxicity led to a period of latency before eventual resumption of inhibited growth. During this period of adaptation, the plasma membrane (PM) H+-ATPase was activated, in coordination with the decrease of intracellular pH (pHi), cell viability and average cell volume. The in vivo activation of this ATPase was demonstrated either by assaying PM-ATPase activity in membrane suspensions extracted from cells grown in the presence or absence of MCPA or by measuring the in vivo H+-pumping activity in the same cells. The PM-H+-ATPase activation could not be attributed to transcriptional activation of the encoding genes PMA1 and PMA2. The activity of PM-H+-ATPase was stimulated and the internal cell volume decreased during yeast adaptation to growth under MCPA stress. Based on the values estimated for the pHi, we hypothesize that these cell responses may contribute to the restoration of pHi homeostasis during recovery from MCPA stress. This work is a contribution to the understanding of the toxic effects of the herbicide MCPA and of physiological mechanisms underlying adaptation to MCPA, in the eukaryotic model S. cerevisiae. Results may be useful to elucidate the adaptation mechanisms to this xenobiotic compound in more complex and experimentally less-accessible eukaryotes. They also provide indications to assist the use of yeast cells as a bioassay system to assess the toxicity of phenoxyacetic acid herbicides and of other lipophilic xenobiotics, aiming at reducing the use of animals in toxicity testing.

SORPTION OF PHENOXYACETIC ACID HERBICIDES ON THE KAOLINITE MINERAL SURFACE – AN AB INITIO MOLECULAR DYNAMICS SIMULATION

Full atomic position optimizations and ab initio molecular dynamics simulations at room temperature were performed in a study of the adsorption of phenoxyacetic acid herbicides on the octahedral surface of a kaolinite layer formed from hydroxyl groups. The studied molecules are bound strongly to the surface hydroxyl groups via hydrogen bonds formed through the carboxyl group. Particularly strong bonding with the hydrogen atom approximately midway between the two adjacent oxygen atoms was observed between the OH group of the carboxyl group and one of the surface OH groups. Molecular dynamics simulations showed proton jumps within this strong hydrogen bond. Kaolinite surface hydroxyl groups are chemically active and able to act as proton donors or acceptors. Additional interactions were observed between atoms of the aromatic parts of the adsorbed molecules and the surface hydroxyl groups. The phenoxyacetic acids are significantly more strongly bound than acetic acid to the octahedral kaolinite surface. This strong bonding of the phenoxyacetic acids to the kaolinite layer surface indicates a strong retention capability in the soil matrix and a significant contribution of kaolinite clay minerals to the “bound residue” phenomenon.

Multiresidue determination of acidic pesticides in water by HPLC-DAD with confirmation by GC-MS using conversion to the methyl ester with trimethylsilyldiazomethane.

A multiresidue pesticide methodology is studied and results for acidics are reported here, with base/neutral to follow. This work studies a literature procedure as a possible general approach to many pesticides and potentially other analytes that are considered to be liquid chromatographic (LC) candidates, rather than gas chromatographic (GC) ones. The analysis of the sewage effluent of a major southwestern U.S. city serves as an example of the application of the methodology to a real sample. Recovery studies were also conducted to validate the proposed extraction step. A gradient elution program was followed for the high-performance LC (HPLC) leading to a general approach for acidics. Confirmation of identity was by electron ionization-GC-mass spectrometry (MS) after conversion of the acids to the methyl ester (or other appropriate methylation) by means of trimethylsilyldiazomethane. The 3,4-dichlorophenoxyacetic acid is used as an internal standard to monitor the reaction, and polychlorobiphenyl #19 is used for the quantitation internal standard. Although others have reported similar analyses of acids, conversion to the methyl ester is by means of diazomethane itself, rather than by the more convenient and safe trimethylsilyldiazomethane. Thus, the present paper supports the use of trimethylsilyldiazomethane with all of these acids (trimethylsilyldiazomethane has been used in environmental work with some phenoxyacetic acid herbicides) and further supports the usefulness of this reagent as a potential replacement for diazomethane. The HPLC approach here could also serve as the separation basis for an LC-MS solution for confirmation of identity, as well as quantitation.

Optimization and validation of an enzyme immunoassay for the insect growth regulator fenoxycarb

A competitive enzyme-linked immunosorbent assay (ELISA) was developed for the quantitative detection of the insect growth regulator fenoxycarb. Polyclonal rabbit antisera, raised against protein conjugates of four haptenic derivatives of fenoxycarb, were utilized in immobilized antigen-based, competitive immunoassays. With ELISA systems that were both hapten- and carrier-heterologous, most antiserum titers fell in the range of 1:1000–1:30,000. Assay conditions, including concentrations of antisera and coating antigens, were optimized. The effect of pH, organic solvents, and various blocking agents was also investigated. A hapten-homologous and two hapten-heterologous indirect ELISAs allowed fenoxycarb determination in the range of 0.1–85 ng ml −1 with apparent IC 50 values of 1.2–2.8 ng ml −1. Cross-reactivities with a number of compounds (e.g. pesticides of related structure, hapten synthesis intermediates, fenoxycarb metabolite, photodegradation products) were determined, and the assay proved highly selective for fenoxycarb. In particular, no significant interference was found with selected pyrethroid and juvenile hormone analog insecticides, phenoxyacetic acid herbicides, and photodegradation products of fenoxycarb. Using spiked water samples, assay performance was validated by SPME/GC-MS.

Toxicity of chlorinated phenoxyacetic acid herbicides in the experimental eukaryotic model Saccharomyces cerevisiae: role of pH and of growth phase and size of the yeast cell population

The inhibitory effect of the herbicides 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D) in Saccharomyces cerevisiae growth is strongly dependent on medium pH (range 2.5–6.5). Consistent with the concept that the toxic form is the liposoluble undissociated form, at values close to their p K a (3.07 and 2.73, respectively) the toxicity is high, decreasing with the increase of external pH. In addition, the toxicity of identical concentrations of the undissociated acid form is pH independent, as observed with 2,4-dichlorophenol (2,4-DCP), an intermediate of 2,4-D degradation. Consequently, at pH values above 3.5 (approximately one unit higher than 2,4-D p K a), 2,4-DCP becomes more toxic than the original herbicide. A dose-dependent inhibition of growth kinetics and increased duration of growth latency is observed following sudden exposure of an unadapted yeast cell population to the presence of the herbicides. This contrasts with the effect of 2,4-DCP, which essentially affects growth kinetics. Experimental evidences suggest that the acid herbicides toxicity is not exclusively dependent on the liposolubility of the toxic form, as may essentially be the case of 2,4-DCP. An unadapted yeast cell population at the early stationary-phase of growth under nutrient limitation is significantly more resistant to short-term herbicide induced death than an exponential-phase population. Consequently, the duration of growth latency is reduced, as observed with the increase of the size of the herbicide stressed population. However, these physiological parameters have no significant effect either on growth kinetics, following growth resumption under herbicide stress, or on the growth curve of yeast cells previously adapted to the herbicides, indicating that their role is exerted at the level of cell adaptation.

AQR1 Gene (ORF YNL065w) Encodes a Plasma Membrane Transporter of the Major Facilitator Superfamily That Confers Resistance to Short-Chain Monocarboxylic Acids and Quinidine in Saccharomyces cerevisiae

We report results on the functional analysis of Saccharomyces cerevisiae ORF YNL065w, predicted to code for a protein belonging to the poorly characterized major facilitator superfamily (MFS) of transporters that are involved in multidrug resistance (MDR). YNL065w is important for a moderate increase of yeast tolerance to ketoconazole and to the cationic dye crystal violet; it protects the cell against short-chain monocarboxylic acids (C2–C6), but not against highly liposoluble acids such as octanoic acid or the phenoxyacetic-acid herbicides 2,4-D and MCPA; it is also a determinant of resistance to the antiarrhytmic and antimalarial drug quinidine. The encoding ORF was, thus, denominated the AQR1 gene. Results obtained using an AQR1-lacZ fusion indicate that gene expression is very low and it is not stimulated under weak acid stress. The encoded putative transporter was localized in the plasma membrane by fluorescence microscopy observation of the overproduced Aqr1-GFP fusion protein distribution.

Saccharomyces cerevisiae Resistance to Chlorinated Phenoxyacetic Acid Herbicides Involves Pdr1p-Mediated Transcriptional Activation of TPO1 and PDR5 Genes

The transcription regulator Pdr1p is a determinant of Saccharomyces cerevisiae resistance to 2-methyl-4-chlorophenoxyacetic acid (MCPA) and 2,4-dichlorophenoxyacetic acid (2,4-D). The Pdr1p-regulated genes, TPO1 and PDR5, encoding putative multidrug transporters belonging to the major facilitator superfamily (MFS) and to the ATP-binding cassette (ABC) superfamily, respectively, are required for yeast resistance to sudden exposure to these herbicides. A rapid and transient activation of TPO1 (sixfold) and PDR5 (twofold) transcription takes place during the adaptation period preceding cell division under MCPA or 2,4-D moderate stress. These activations are mediated by both Pdr1p and Pdr3p and, as soon as adapted cells start duplication under herbicide stress, mRNA levels are drastically reduced to basal values. The longer duration of the adaptation period, observed for the Δpdr1 population, may involve the abolishment of the Pdr1p-mediated transcriptional activation of TPO1 and PDR5 genes, whose expression is critical to surpass the viability loss during the initial period of adaptation to the herbicides.

Synthesis of haptens and protein conjugates for the development of immunoassays for the insect growth regulator fenoxycarb.

Sensitive and selective enzyme-linked immunosorbent assays (ELISAs) in the immobilized antigen format were developed for fenoxycarb (1), an insect growth regulator (IGR). The parent molecule [ethyl 2-(4-phenoxyphenoxy)ethylcarbamate] was derivatized at several positions to obtain haptens (2-5) that were used to produce protein conjugates and rabbit polyclonal antisera. Amino derivatives of fenoxycarb at the terminal and internal rings (2 and 3, respectively) were linked to carrier proteins by azo coupling. Carboxyalkyl-spacer groups were attached to the ethyl group and the nitrogen atom of the target compound (1) to obtain haptens 4 and 5, respectively. Hapten-homologous ELISAs based on protein conjugates of compounds 2 and 4 determined fenoxycarb in the mid-ppb range (IC(50), 102 and 95 ppb, respectively). A more sensitive hapten-heterologous ELISA (IC(50), 17 ppb; detection limit 0.5 ppb) involved the antiserum raised against a conjugate of hapten 2 and the plate-coating antigen obtained from compound 3. These assays displayed no significant interferences with photodegradation products of fenoxycarb, the IGRs methoprene and pyriproxyfen, and a variety of pesticides including the pyrethroids fenvalerate and cypermethryn, the phenoxyacetic acid herbicide 2,4-D, DDT, and the nitrodiphenyl ether herbicides acifluorfen and fluorodifen.

Prenatal developmental effects of pure 2,4‐dichlorophe‐noxyacetic acid (2,4‐D) on the rat

ABSTRACT 2,4‐Dichlorophenoxyacetic acid (2,4‐D) a plant growth regulator, has been used worldwide as an herbicide. The phenoxyacetic acid herbicides contain both 2,4‐D and 2,4,5‐Trichlorophenoxyacetic acid (2,4,5‐T) along with emulsifiers, solvents and contaminants; these have been recognized as teratogen in the rat and mouse. Although the high teratogenicity of phenoxyacetic herbicides has been attributed to the 2,4,5‐T and the contaminant 2,3,7,8‐tetrachlorodibenzo‐p‐dioxin (TCDD), the possibility that 2,4‐D might play a role has not been clearly ruled out We designed this study to evaluate the effects of pure 2,4‐D, and herein describe the precise fetal visceral malformations. We randomly distributed pregnant Wistar rats in to three main groups according to organogenesis during which pure 2,4‐D was administered at different doses: l)‐over all organogenesis (gestational days 6 to 15), 2)‐early organogenesis (gestational days 6 to 10), and 3)‐late organogenesis (gestational days 11 to 15). We found that the pure 2,4‐D is maternally toxic and has a dose‐related embryolethality. The visceral malformations induced in the fetuses included ureteric dilatations and hydronephrosis, as reported, in conjunction with the herbicide forms. In addition, we observed an association with renal and urogenital aplasia, which were observed in the early organogenesis period. We performed a histopatho‐logical examination and discussed the mechanism of the pathological processes. We conclude that the pure 2,4‐D itself is maternally toxic and embryolethal, and potential inducer of kidney and urogenital malformations in the rat. The types of kidney and urogenital malformations seen indicated that the 2,4‐D interferes in the early developmental stage of the urogenital system.

Trans-Activation of PPARα and PPARγ by Structurally Diverse Environmental Chemicals

A large number of industrial chemicals and environmental pollutants, including trichloroethylene (TCE), di(2-ethylhexyl)phthalate (DEHP), perfluorooctanoic acid (PFOA), and various phenoxyacetic acid herbicides, are nongenotoxic rodent hepatocarcinogens whose human health risk is uncertain. Rodent model studies have identified the receptor involved in the hepatotoxic and hepatocarcinogenic actions of these chemicals as peroxisome proliferator–activated receptor alpha (PPARα), a nuclear receptor that is highly expressed in liver. Humans exhibit a weak response to these peroxisome proliferator chemicals, which in part results from the relatively low level of PPARα expression in human liver. Cell transfection studies were carried out to investigate the interactions of peroxisome proliferator chemicals with PPARα, cloned from human and mouse, and with PPARγ, a PPAR isoform that is highly expressed in multiple human tissues and is an important regulator of physiological processes such as adipogenesis and hematopoiesis. With three environmental chemicals, TCE, perchloroethylene, and DEHP, PPARα was found to be activated by metabolites, but not by the parent chemical. A decreased sensitivity of human PPARα compared to mouse PPARα to trans-activation was observed with some (Wy-14,643, PFOA), but not other, peroxisome proliferators (TCE metabolites, trichloroacetate and dichloroacetate; and DEHP metabolites, mono[2-ethylhexyl]phthalate and 2-ethylhexanoic acid). Investigation of human and mouse PPARγ revealed the transcriptional activity of this receptor to be stimulated by mono(2-ethylhexyl)phthalate, a DEHP metabolite that induces developmental and reproductive organ toxicities in rodents. This finding suggests that PPARγ, which is highly expressed in human adipose tissue, where many lipophilic foreign chemicals tend to accumulate, as well as in colon, heart, liver, testis, spleen, and hematopoietic cells, may be a heretofore unrecognized target in human cells for a subset of industrial and environmental chemicals of the peroxisome proliferator class.

PREVALENCE OF ANTINUCLEAR ANTIBODIES IN A RURAL POPULATION

Exposure to environmentally and occupationally encountered toxicants can be associated with the development of certain autoimmune diseases and with the induction of antinuclear antibodies (ANA). Some chemicals used in the agricultural industry are known to affect immune function but their roles in the induction of autoimmunity in general, and ANA in particular, have not been reported previously. This study was undertaken to establish the prevalence of ANA in a rural population and to determine environmental and occupational exposures with which they are associated. This cross-sectional study represented one component of an interdisciplinary project (Prairie Ecosystem Study [PECOS], Eco-Research Program, Tri-Council Secretariat of Canada) designed to explore, in a rural population, the roles of environmental exposures as determinants of human health status. Information regarding lifetime, current, and main occupational exposures in the rural-dwelling study population was derived from a self-administered questionnaire. Sera from consenting subjects, collected during the months of February and March 1996, were assayed for ANA by indirect immunofluorescence on HEp-2 cells. The study population comprised 322 adult subjects (mean age 49.3 +/- 14.7 yr; range 16-87 yr). Statistical analyses adjusted for age and sex revealed that the presence of ANA among the participants was associated with a current agricultural occupation that included oilseed production, hog production, or poultry production. There was a significant association between ANA positivity and a current main farming operation of crop production. There was also an association among individual participants between lifetime exposure to the insecticide class of pesticides and the presence of ANA. In this rural study population, ANA positivity was significantly associated with lifetime exposure specifically to carbamate, organochlorine (including aldrin, chlordane, dieldrin, endrin, heptachlor, and lindane, but excluding DDT and methoxychlor), and pyrethroid insecticides and to phenoxyacetic acid herbicides, including 2,4-D. After adjustment for age, sex, and other insecticide exposures, multivariate analyses indicated that ANA positivity was associated with current oilseed production and with lifetime exposure to pyrethroid insecticides. In a rural population, ANA were associated with production of certain crops and certain animals and exposure to specific pesticides. The data indicate that some occupational exposures related to the agricultural industry are associated with the presence of ANA, a serologic expression of autoimmunity.

Overexpression of mdr2 gene by peroxisome proliferations in the mouse liver

Background: In mice, fibrates induce mdr2 gene expression, and its encoded P-glycoprotein in the canalicular domain of hepatocytes, as well as increasing biliary phospholipid output. It is not known whether this effect is restricted to fibrates or is a common property of peroxisome proliferators. Aims: To test the effect of structurally unrelated pero-oxisome proliferators on mdr2 gene expression and biliary phospholipid output, and to explore the molecular mechanism(s) of mdr2 gene induction. Methods: Male CFI mice were fed on a diet supplemented with several peroxisome proliferators: phenoxyacetic acid herbicides, plasticizers, acetylsalicylic acid and partially hydrogenated fish oil. Results: Increased levels of mdr2 mRNAs, assessed by Northern blot analysis, were observed in the liver of mice treated with phenoxyacetic acid herbicides: 2,4,5-trichlorophenoxyacetic acid 570±133%, 2,4-dichlorophenoxyacetic acid 233±54% ( p<0.005); plasticizers: di-(2-ethylhexyl)phthalate 282±78%, di(isoheptyl)phthalate 163±40%, phthalic acid dinonyl ester 225±48% ( p<0.01); and partially hydrogenated fish oil 372±138% ( p<0.005). P-glycoprotein traffic ATPase content increased in the canalicular domain of hepatocyte of mice treated with the herbicide 2,4,5-trichlorophenoxyacetic acid and with partially hydrogenated fish oil (108% and 87%, respectively, p<0.05) as well as biliary phospholipid output (106% and 74%, respectively, p<0.05). In 2,4,5-trichlorophenoxyacetic acid-fed mice we found five-fold increase on mdr2 transcription rate, assessed by nuclear run-off assay. Conclusions: Peroxisome proliferations induce mdr2 gene, its encoded P-gp in the canalicular domain of hepatocytes and increase biliary phospholipid output. The modulation of mdr2 gene might be part of the pleiotrophic response of peroxisome proliferation in mice liver and seems to be regulated mainly at a transcriptional level.

Biodegradation of the herbicides 2,4‐dichlorophenoxyacetic acid, 2,4,5‐trichlorophenoxyacetic acid, and 2‐methyl‐4‐chlorophenoxyacetic acid in a sulfate‐reducing aquifer

AbstractBiodegradation of trace organic compounds is one of the main mechanisms to purify infiltrating surface water during bankfiltration and underground passage. In anaerobic zones of the underground, rate and extent of degrading processes may be totally different from those in aerobic ones. To investigate this, a model ecosystem was built that reproduces an anaerobic part of the aquifer and the behavior of the three phenoxyacetic acid herbicides 2,4‐dichlorophenoxyacetic acid, (2,4‐D), 2,4,5‐trichlorophenoxyacetic acid (2,4,5‐T), and 2‐Methyl‐4‐chlorophenoxyacetic acid (MCPA) tested. In anaerobic experiments with varying conditions they proved to be almost persistent. Only under aerobic conditions could biodegradation be observed after a lag period. © by John Wiley &amp; Sons, Inc.

Behaviour of Phenoxyacetic Acids During Underground Passage with Different Redox Zones

The behaviour of the three phenoxyacetic acid herbicides 2,4-D, 2,4,5-T and MCPA during underground passage and bankfiltration was tested in a model system consisting of laboratory filter columns filled with natural underground materials. Different redox environments were reproduced by operating the filters with natural aerobic and anaerobic groundwater. In the presence of oxygen, biodegradation of the three herbicides started after a lag phase. Under sulfate reducing conditions, no degradation could be observed. To assess the factors that may influence microbial degradation in the anaerobic environment, the concentration of herbicides, the time and the nutrient content were varied, but this did not increase degradation. The maximum retention of the herbicides in the filters was 30%, mainly due to adsorption to the filter material.

The role of occupational exposure and immunodeficiency in B-cell malignancies. Working Group on the Epidemiology of Hematolymphopoietic Malignancies in Italy.

Excesses of non-Hodgkin's lymphoma have been observed among farmers exposed to phenoxyacetic acid herbicides and, less persuasively, among workers exposed to insecticides. Exposure to organic solvents (particularly chlorinated hydrocarbons) has also been associated with an increased risk of NHL. TCDD (which is a contaminant of phenoxy herbicides), DDT, and chlorinated solvents have all been reported to induce impairment or suppression of cell-mediated immunity. We hypothesize that NHL is caused by common viruses, such as the Epstein-Barr virus, that induce proliferation and immortalization of B-cells, followed by T-cell impairment entailing cell-mediated immunodeficiency. The increased risk of NHL with HIV infection and heart or kidney transplantation, in which immunodeficiency also occurs, is consistent with this hypothesis.

Biological Treatment of a Landfill Leachate Containing Phenoxy Herbicides and Chlorophenols

A biological treatment process has been developed for a landfill leachate containing phenoxyacetic acid herbicides and their associated chlorophenols. The mixed microbial population (Pseudomonas sp.) enriched from soil was capable of mineral ising the key phenoxy components and has been found to be stable over 700 days in continuous culture, removing 99.5 % of phenoxies and 96.7 % of chlorophenols. Toxicity tests using D.magna and Microtox systems have shown a 90 % reduction in toxicity by biological treatment. A laboratory activated sludge system was developed resulting in complete degradation of the chlorophenols and phenoxies.