An overview of short‐term tests for the mutagenic and carcinogenic potential of pesticides

Abstract

In the last few years, marked progress has been made in the development of methods for evaluating the mutagenic and carcinogenic potential of pesticide chemicals. The correlation of genetic and related biological activity in short‐term tests with carcinogenic activity in whole animals allows the utilization of short‐term mutagenicity bioassays to prescreen chemicals for effects related to mutation induction and presumptive carcinogenicity. In addition, bioassays now available can measure directly the chemical transformation of normal cells in culture into cells capable of producing tumors when injected into animals.

This paper will review briefly the major types of relevant short‐term tests and will develop a rationale for a phased approach to the evaluation of the mutagenic and carcinogenic potential of environmental chemicals. This approach involves the sequential application of bioassays which are organized into a three‐level matrix emphasizing first detection, then confirmation, and finally hazard assessment. Chemicals demonstrating positive results in the short‐term detection systems and confirmatory bioassays are pursued in higher level whole animal tests. A core battery of tests is proposed to operationally define a negative result. The phased approach should facilitate a cost effective utilization of limited testing resources and provide protection for human health in proportion to the anticipated hazard.

Results obtained in evaluating a series of thirty‐eight pesticide chemicals according to the phased approach are discussed in detail.     

EDS and μ-XRF mapping of amalgam degradation products in ancient mirrors

An amalgam mirror is a mirror type, used from the fifteenth century until the end of the nineteenth century, where the reflective layer is constituted by a tin amalgam layer adhered to a glass sheet. In this work, two amalgam mirrors samples were studied by scanning electron microscopy with an energy dispersive spectrometer and by micro-X-ray fluorescence elemental mapping to go deeply into the understanding of the degradation mechanism of the amalgam layer of ancient mirrors. The investigation has been focused for the first time on the reflective surface of the amalgam layer adherent to the glass sheet to better understand the processes of amalgam corrosion. The two amalgam degradation compounds, romarchite and cassiterite, has been spatially differentiated by scanning electron microscope (SEM) and energy dispersive spectrometer (EDS) maps. SEM images and micro-X-ray fluorescence and EDS maps showed that the amalgam degradation products grow up to form hemispherical stratified calottes. This structure is probably due to a mechanism involves cyclic phases and oxygen radial diffusion from a superficial oxidation nucleus.     

A model of natural degradation of 17-α-ethinylestradiol in surface water and identification of degradation products by GC-MS

Over the past decade, the environment has been polluted by a wide spectrum of exogenous chemicals and environmental analysis has become one of the most progressive parts of analytical research. The aim of this work was to determine the kinetics of natural degradation, and to identify the degradation products of the massively used estrogenic drug, 17-α-ethinylestradiol. The photodegradation, oxidation and thermostability conditions were selected according to ICH requirements for pharmaceutical stability testing. A simple 72-h photodegradation study in purified water exhibited significant first-order kinetics with the kinetic constant k = 0.0303 h^?1, and degradation halftime 22.8 h. The basic halftime could be reduced to 17.1 h by the addition of sea salt, and increase in temperature. Monohydroxy, dihydroxy and dehydrogenated derivatives of ethinylestradiol with intact steroidal structure were identified as major degradation products resulting from simple photodegradation. The addition of an oxidative agent significantly accelerated the degradation rate; combined with higher temperature, the degradation halftime was reduced to 1.1 h with the first-order kinetic constant k = 0.632 h^?1. TOC analysis showed a notable decrease of organic mass (18% in 3 days) during oxidation experiments, and confirmed the degradation of steroidal structure.

     

Determination of T‐2 toxin in grain and grain products by HPLC and TLC

Abstract

The purpose of this study was to investigate the T‐2 toxin contaminated grain and grain products consumed especially by Turkish population. The T‐2 toxin was detected using the high performance liquid chromatography (HPLC) with UV detector at 208 nm and the identify of T‐2 was further confirmed by thin layer chromatography (TLC). The recovery was 91 ±4.24% for corn flour fortified with the known amount of T‐2 toxin (1 ppm). The detection limits of T‐2 toxin for the HPLC and the TLC were 25 ng and 50 ng, respectively. A total of 30 commercially available grain and grain product samples were analyzed. Two corn flour samples were found to contain detectable levels of T‐2 toxin at a level of 1.60 ppm and 4.08 ppm.     

Fabrication of ZnO–SnO2 nanocomposite and its photocatalytic activity for enhanced degradation of Biebrich scarlet

Environmental Science and Pollution Research - The n–n-type ZnO–SnO2 nanocomposite was fabricated using malic acid following a simple one-pot co-precipitation method. The fabricated...     

Short‐chain fatty acids affect cell‐association and invasion of HEp‐2 cells by Salmonella typhimurium

Abstract

This study demonstrates that the growth of S. typhimurium in Luria Bertani broth supplemented with acetate, propionate, butyrate, or a mixture of the three SCFA, affected cell‐association and the ability to invade cultured HEp‐2 cells. Cell‐association and invasion was determined after growth for 4 h of growth in the presence of the SCFA at pH 6 and 7. The results suggest that the growth rate of the culture may have affected cell‐association and invasion since accompanying the significant decrease in growth rate in the presence of SCFA at pH 6 was a decrease in cell‐association and invasion. However, the results also suggest that the individual SCFA may play a role in modulating cell‐association and the invasion phenotype and the regulation of cell‐association and invasion by the SCFA was dependent on the concentration and the pH of the medium. Although the growth rates were similar for S. typhimurium in the SCFA mixture, butyrate (100 mM) and propionate (50 mM) at pH 6, differences in cell‐association and invasion were observed among these cultures. Also, at pH 7, differences were observed among the SCFA treatments even though the growth rates were similar.     

Evaluation of methodology for determining 1,2‐dibromoethane (EDB) in ambient air

Abstract

EDB (ethylene dibromide) is of regulatory interest because it has cancer inducing properties and is a causative agent of aspermia. Methodology used in determining the extent of exposure of workers to EDB in a citrus fumigation facility was evaluated. The purpose of this effort was to develop and/or evaluate the methodology. A number of solid adsorbents were evaluated for trapping EDB. Charcoal was found to be the most efficient for this application. The influence of a number of factors, e.g., humidity, biphenyl concentration and solvents, on trapping and elution efficiency was determined. The level of sensitivity attained in these studies exceeds that necessary to monitor the proposed standard of a maximum of 1 mg/m³ for a 15 min occupational exposure.     

Differential enhanced degradation of cis‐ and trans‐1,3‐D in soil with a history of repeated field applications of 1,3‐D

Abstract

The fumigant 1,3‐dichloropropene (1,3‐D) is considered to be a potential alternative to methyl bromide. The degradation rates of cis‐ and trans‐l,3‐D in soil from a treated site during three successive annual applications of 1,3‐D progressively increased with an increase in the number of annual applications. The enhancement was greater for trans‐l,3‐D degradation than cis‐l,3‐D. In untreated soil, the degradation rates of the two isomers were similar. The enhancement lasted slightly longer than 2 years after annual field application of 1,3‐D had ceased. A single field reapplication of 1,3‐D to the treated site that had not been treated for 2 years resulted in resumed differential enhanced degradation of cis‐ and trans‐l,3‐D. Microorganisms were responsible for the enhanced degradation.     

Evaluation of C18 solid‐phase extraction cartridges for the isolation of select pesticides and metabolites

Abstract

Nine different C₁₈ solid‐phase extraction (SPE) cartridges were evaluated for their efficiency at extracting nine pesticides and two s‐triazine metabolites from spiked deionized water samples. The SPE cartridges were found to contain nitrogen (N) and/or phosphorus (P) contaminants and varied in their extraction efficiency for certain pesticides and metabolites. Four of the nine SPE cartridges gave acceptable (70 to 120%) pesticide and metabolite recovery percentages, while five cartridges had marginal (50 to 70%) to poor (< 50%) recoveries. Statistical analyses showed that the poor to marginal recoveries found for three compounds could not be explained by considering several indigenous chemical and physical traits of the cartridge. It is suggested that proper SPE cartridge selection for pesticide recovery should be evaluated using several different cartridges.     

Biological activity and bioavailability of grain bound 14C‐malathion residues in rats

Abstract

Paddy (unmilled rice), milled rice and maize‐bound ¹⁴C residues were prepared using ¹⁴C‐succinate‐labelled malathion at 10 and 152 ppm. After 3 months, the bound residues accounted for 12%, 6.5% and 17.7% of the applied dose in paddy, milled rice and maize respectively in the grains treated at 10 ppm. The corresponding values for the 152 ppm were 16.6%, 8.5% and 18.8%. Rats fed milled rice ‐ bound ¹⁴C‐residues eliminated 61% of the ¹⁴C in the faeces and 28% in the urine. The corresponding percentages for paddy and maize were 72%, 9% and 53%, 41% respectively; indicating that bound residues from milled rice and maize were moderately bioavailable. When rice‐bound malathion residues (0.65 ppm in feed) were administered to rats in a 5 week feeding study, no signs of toxicity were observed. Plasma and RBC cholinesterase activities were slightly inhibited: blood urea nitrogen was significantly elevated in the test animals. Other parameters examined showed no or marginal changes.     

Evaluation of Beta‐naphthoxyacetic Acid for Mutagenic Activity in the Salmonella/mammalian Microsome Assay

1,3‐β‐d‐Glucan derived from baker's yeast was chemically modified in two steps yielding crosslinked carboxymethyl glucan as the sodium salt (2). After cation exchange with hexadecyltrimethylammonium chloride, a hydrophobic adsorbent (3) was obtained which showed an excellent binding of the estrogenic mycotoxin zearalenone with a maximum adsorption of up to 183 mg/g. Compound 3 additionally showed a relatively high adsorption capacity for the trichothecene T‐2 toxin of at least 10 mg/g. Starting from 2, various derivatives were prepared by cation exchange using quaternary ammonium salts bearing substituents besides methyl from four to 18 carbon atoms. The adsorption of T‐2 toxin on these derivatives were compared with compound 3 leading to the conclusion that 3 is the best adsorbent of all investigated tetraalkylammonium‐modified derivatives of 2.     

Accelerated degradation of carbofuran in standing water from carbofuran‐retreated Azolla plots

Abstract

Carbofuran (2, 3‐dihydro‐2, 2‐dimethyl‐7‐benzofuranyl N‐methylcarbamate) was mixed with standing water from six flooded Azolla (a fern harboring a nitrogen fixing alga, Anabaena azollae) plots that had been regularly treated with carbofuran before. The insecticide completely disappeared in 5 to 10 days when mixed with water from three of the six plots. The enrichment culture, prepared by further additions of carbofuran to the standing water from an Azolla plot, degraded bendiocarb (2, 2‐dimethyl‐l, 3‐benzidioxol‐4‐yl‐N‐methylcarbamate), carbofuran and carbosulfan [2,3‐dihydro‐2,2‐dimethyl‐7‐benzofuranyl (di‐n‐butyl‐aoinosulfenyl) methyl‐carbamate ] in that order. Enrichment culture, upon sterilization by autoclavlng, lost its ability to degrade carbofuran. Evidently, accelerated degradation of carbofuran in standing water from retreated Azolla plots was mediated by microorganisms.     

Development and application of methodology for determining 1,2‐dibromo‐3‐chloropropane (DBCP) in ambient air

Abstract

Ametpreviously described by Mann et al.¹ for the determination of hexachlorobenzene in air was modified to detect DBCP in air at the level of 0.02 ppb (by volume). The method utilizes Chromosorb 101 as a trapping medium with subsequent analysis of the eluted DBCP by electron capture ‐ gas chromatography. The procedure was tested using air flows of 1 1/min to 5 1/min for sampling periods of 30 min to 3 hr. Recoveries of greater than 90% were obtained for DBCP levels ranging from 0.07 ppb to 20 ppm. More than 90% of the DBCP stored on Chromosorb 101 at ambient temperature for one month was recovered. A one‐half acre field plot was sprayed with DBCP using the drench method. Air samples were taken from the breathing zone of the applicator during the mixingspraying and clean‐up procedures. Air samples were also taken periodically around the perimeter of the plot for up to 7 days after spraying.     

Potential of 2, 4‐dichlorophenoxyacetic acid conjugates as promutagens in the salmonella/microsome mutagenicity test

Abstract

Hepatic S9 preparations from Aroclor 1254 induced rats and 3‐methylcholanthrene induced woodchucks were used to investigate, in vitro, the mutagenic potential of five amino acid conjugates of 2, 4‐Dichlorophenoxyacetic acid (alanine, aspartic acid, leucine, methionine and tryptophan). Five strains of Salmonella typhimurium (TA97, TA98, TA100, TA1535, TA1538) were utilized for this purpose. Dose‐response effects producing a two‐fold increase of revertants over spontaneous levels were not observed with either S9 preparation indicating that the amino acid conjugates are not promutagens in these assays.     

The degradation of anilazine and dihydroxy‐anilazine at various soil depths of an orthic luvisol

Abstract

In conformity with Guideline 4.1 of the Federal German Biological Agency, degradation experiments with the fungicide active ingredient [benzene ring‐U‐¹⁴C]anilazine and its major metabolite [triazine ring‐U‐¹⁴C]dihydroxy‐anilazine were carried out in an orthic luvisol. Mineralization of the benzene ring carbon of anilazine amounted to less than 2 % in 110 days and that of the triazine ring carbon of dihydroxy‐anilazine to less than 8 %. Increasing the incubation temperature from 22 °C to 30 °C and adding organic substance influenced the mineralization slightly. In soils which received two or three applications in succeeding years with subsequent ageing in the open‐air lysimeter no stimulation of the mineralization was observed. Extractions after incubation showed that only 10.2 to 18.6 % of the ¹⁴C‐activity applied with anilazine was extractable with acetone/CaCl₂. The major proportion was bound in the fractions of the soil organic matter, namely 45.0 to 59.6 % of the radiocarbon applied was accounted for by the humin fraction, 12.0 to 27.4 % by the fulvic acids, and 9.4 to 15.0 % by the humic acids. In the case of dihydroxy‐anilazine, 28.9 to 89.7 % of the applied ¹⁴C‐activity was extractable with acetone/CaCl₂. Of tJhe radiocarbon bound in the soil, the greatest proportion, i.e. 18.5 to 35.5 % of the radiocarbon applied, was accounted for by the fulvic acids.     

Solubility products of six metal‐glyphosate complexes in water and forestry soils,and their influence on glyphosate toxicity to plants

Abstract

The solubility products (K_sp) of 1:1 complexes of glyphosate, [N‐(phosphonomethyl)glycine], with Mg²⁺, Ca²⁺, Mn²⁺, Zn²⁺, Cu²⁺ and Fe³⁺, were determined in buffered (pH 7.0) distilled water, moist Ottawa sand, sandy loam and clay loam soils, each adjusted to 0.02 M with respect to KNO₃. The K_sp values decreased in the order of Mg ? Ca > Mn > Zn > Cu > Fe, regardless of the medium in which they were determined. The constants measured in Ottawa sand were similar to those in water, but those in the forestry soils depended upon the type of metal ion involved. The values for the Mg, Ca, Mn and Zn complexes were about 2 to 3 times lower in sandy loam soil than those in water, but those in clay loam were about 3 to 10 times lower. The K_sp of the Cu and Fe complexes were similar to those in water regardless of the soil type used.

In a bioassay experiment using tomato plants, immersed in the saturated solutions of the complexes or planted in the sand and soils containing saturated solutions of the complexes, no mortality occurred although slight inhibition in growth was observed in all cases. The most soluble complexes of Mg and Ca caused the most reduction in plant height, while the least soluble complex of Fe caused little growth inhibition. The Zn, Cu and Mn complexes caused some growth inhibition depending on their K_sp values. The larger the solubility product, the greater the concentration of glyphosate ion in solution, and the greater the growth inhibition. In a similar experiment using white spruce seedlings, growth inhibition was insignificant over the 12‐d bioassay period.     

Magnetic photocatalysts from δ-FeOOH and TiO2 and application in reactions for degradation of methylene blue and paracetamol with UV-C and sunlight

Environmental Science and Pollution Research - Water contamination is a common problem, especially considering dyes and drugs disposal. A possible and effective treatment method to remove these...     

Effectiveness of UV/SO32− advanced reduction process for degradation and mineralization of trichlorfon pesticide in water: identification of intermediates and toxicity assessment

Environmental Science and Pollution Research - This study aimed to investigate the degradability, mineralization, proposed decomposition pathway, intermediate products, and toxicity of effluent...     

Dissipation of chlorpyrifos,oxon, and 3,5,6‐trichloro‐2‐pyridinol in litter and elm forest soil

Abstract

After chlorpyrifos was applied to the basal 1 meter of elm tree trunks for control of elm bark beetles at two different application times and sites, initial chlorpyrifos residues in forest floor litter ranged from 120 to 916 μg/g depending on the application time. Residues dissipated by approximately 99% after 791 d with the DT₅₀ from 3.9 to 59 d and DT₉₀ from 55 to 310 d. The initial residues of chlorpyrifos in elm forest soil varied from 0.8 to 28 μg/g and were 1 to 2 μg/g at 791 d after application. The dissipation half‐lives of chlorpyrifos in fortified soil placed in the field ranged from 116 to 121 d.     

Application of a LC–MS/MS method for multi-mycotoxin analysis in infant formula and milk-based products for young children commercialized in Southern Brazil

ABSTRACT

An analytical method based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) was validated and applied for the analysis of aflatoxin M₁ (AFM₁), ochratoxin A (OTA) and deoxynivalenol (DON) in infant formula and milk-based products for young children commercialized in Brazil. A total of 38 samples were evaluated, including 12 infant formula, 14 follow-on formula and 12 samples of milk-based products. AFM₁ was detected in 12 (32%) samples, and seven (18%) samples contained AFM₁ levels above the method limit of quantification in a concentration range between 0.013 and 0.067 ng mL^?1 (0.026 ± 0.019). Two samples of milk-based products exceeded the maximum level (ML) fixed by the European Union for AFM₁ in baby foods, however, all samples were in agreement with the levels established by the Brazilian regulation. OTA and DON were not detected in any of the analyzed samples.