Genotoxicity of contaminated soil and shallow well water detected by plant bioassays

Cytogenotoxicity assessment in Allium cepa roots exposed to methyl orange treated with Oedogonium subplagiostomum AP1

The present study is an attempt to assess the cytogenotoxic effect of untreated and methyl orange treated with Oedogonium subplagiostomum AP1 on Allium cepa roots. On the fifth day, root growth, root length, mitotic index, mitotic inhibition/depression, and chromosomal abnormalities were measured in root cells of Allium cepa subjected to untreated and treated methyl orange dye solutions. Roots exposed to treated dye solution exhibited maximum root growth, root length and mitotic index, whereas roots exposed to untreated dye solution had the most mitotic inhibition and chromosomal abnormalities. Allium cepa exposed to untreated dye solution revealed chromosomal aberrations such as disoriented and abnormal chromosome grouping, vagrant and laggard chromosomes, chromosomal loss, sticky chain and disturbed metaphase, pulverised and disturbed anaphase, chromosomal displacement in anaphase, abnormal telophase, and chromosomal bridge at telophase, spindle disturbances and binucleate cells. The comet test was used to quantify DNA damage in the root cells of A. cepa subjected to untreated and treated methyl orange solutions in terms of tail DNA (percent) and tail length. The results concluded that A. cepa exposed to methyl orange induced DNA damage whereas meager damage was noted in the treated dye solution. As a result, the research can be used as a biomarker to detect the genotoxic effects of textile dyes on biota.

Assessment of Metal(loid) Contamination and Genotoxic Potential of Agricultural Soils

Soil, a connecting link between biotic and abiotic components of terrestrial ecosystem, receives different kinds of pollutants through various point and nonpoint sources. Among different sources of soil pollution, contaminated irrigation water is one of the most prominent sources affecting soils throughout the globe. The irrigation water (both surface and groundwater) is increasingly getting polluted with contaminants such as metal(loid)s due to various anthropogenic activities. The present study was conducted to analyze metal(loid) contents in agricultural soil samples (N = 24) collected from fields along the banks of rivers Beas and Sutlej flowing through Punjab state of India, using wavelength-dispersive X-ray fluorescence (WDXRF) spectroscopy. The soil samples were also analyzed for their genotoxic potential using Allium cepa root chromosomal aberration assay. The rivers Beas and Sutlej are contaminated with municipal and industrial effluents in different parts of Punjab. The soil samples analyzed were found to have higher contents of arsenic, cobalt and chromium in comparison with the reference values given by various international agencies. Pollution assessment using different indices like index of geo-accumulation, enrichment factor and contamination factor revealed that the soil samples were highly polluted with cobalt and arsenic. The Allium cepa assay revealed that maximum genotoxicity was found in soil samples having higher contents of As and Co. Pearson's correlation analysis revealed strong positive correlation between the different metal(loid)s which indicated common sources of these metal(loid)s. Therefore, efforts must be taken to reduce the levels of these metal(loid)s in these agricultural soils.

Assessment of surface water using Allium cepa test and histological analysis in Rhamdia quelen

This study aimed to assess the cytotoxic, genotoxic, and mutagenic potentials of water samples collected in the Alegre River Basin, located in a predominantly rural area with no sewage treatment facilities in the Espírito Santo State, Brazil, using Allium cepa test. Also, gills and liver of Rhamdia quelen, a common fish species of the region, were histologically analyzed. A semi-quantitative analysis was performed and a histopathological alterations index (HAI) was determined. Our findings indicated that the waters of this river basin were cytotoxic (mitotic index reduction) and/or genotoxic (chromosomal abnormalities induction). Mutagenicity (micronuclei induction) was not observed for any water sample. The values for HAI showed that the waters caused moderate histological alterations in R. quelen. Liver was more sensitive than gills. It is necessary to implement a sewage treatment system and raise awareness on inappropriate management and disposal of agrochemicals in order to allow the recovery of Alegre River.

Metal bioaccumulation and mutagenesis in a Tradescantia clone following long-term exposure to soils from urban industrial areas and closed landfills

Soil mutagens, particularly metals, may persist long after the source of pollution has been removed, representing a hazard to plants, animals, and humans in or near contaminated areas. Often, due to urban growth, previous land uses may be forgotten and hazards overlooked. We exposed Tradescantia clone #4430 plants to soil from two industrial areas (with different former uses) and two urban waste landfills in the city of Vilnius, all of which were long disused. Two modes of exposure were used: long-term exposure of growing plants in test soils for 0.5 or 1.0y, and short-term exposure of cuttings to water and dimethyl sulfoxide (DMSO) soil extracts. An increased frequency of micronuclei (MN) was observed with both modes of exposure. The concentrations of 24 metals and other elements were analyzed in the test soils and in above-ground plant parts, under both exposure modes, and the concentration coefficients (Cc) for various elements, the total contamination index (Zs) for soils and plants, and the bioaccumulation factor (BAF) for plants were calculated. These measurements allow a comparison of the contamination levels of soils and plants with equalized values. Metal accumulation levels in plants and soils showed significant differences, providing a better understanding of the genotoxicity of soils from closed landfills and highlighting the need to determine the concentrations of metals and other genotoxicants in plants in relation to genotoxicity.

Low-dose toxicity of biogenic silver nanoparticles fabricated by Swertia chirata on root tips and flower buds of Allium cepa

Chemically synthesized silver nanoparticles (chem-AgNPs) have been assessed extensively to show adverse effects on plant cells but the role of biologically synthesized nanoparticles (bio-AgNPs) at lower concentrations and their toxicological impact on plant cells have not been sufficiently studied. In this study, bio-AgNPs were prepared using aqueous leaf extracts of Swertia chirata. This AgNPs showed absorption peak at 440nm of the visible spectrum. TEM analysis revealed that the average size of AgNPs were 20nm and mainly spherical in shape. AFM topographic images depicted the three dimensional aspects of AgNPs. XRD analysis confirmed the crystalline nature. FTIR spectrum of the AgNPs revealed the possible biomolecules involved in bioreduction and efficient stabilization of the particles. Low-dose of bio-AgNPs concentrations (5, 10 and 20μgml^-1) were used for toxicity studies on Allium cepa. The studies revealed that various chromosomal aberrations were induced in both mitotic and meiotic cells of Allium cepa even at lower concentrations of bio-AgNPs. Abnormalities in post meiotic products were also observed. Both mitotic and meiotic indexes decreased with increasing concentrations of bio-AgNPs in the treated cells. These findings implied that low dose bio-AgNPs can induce significant clastogenic effects on both meristematic and reproductive plant cells.

Evaluation of herbicides action on plant bioindicators by genetic biomarkers: a review

The use of pesticides has increased worldwide, owing to the demand for products of good quality and to satisfy a growing population. Herbicides represent almost half of the total amount of pesticides used. Although important to the reduction of costs and an increase of productivity, their indiscriminate use, as well as that of the other pesticides, is a global environmental problem, since they affect the living organisms. To evaluate the damage caused by herbicides to the environment, different organisms have been used as bioindicators, especially higher plants, due to several advantages. This is a literature review on herbicidal actions in plant bioindicators, as assessed by genetic biomarkers. Also, the present manuscript aimed to characterize the main organisms (Allium cepa, Vicia faba and Tradescantia spp.) and the most used biomarkers (mitotic index, chromosome aberrations, micronuclei, sister chromatid exchange and mutations). We concluded that herbicides induce cytotoxicity and genotoxicity in the assessed bioindicators. The data corroborate the existing warnings of the risks that the indiscriminate and increasing use of pesticides poses to the environment and its biodiversity.

Cytotoxic, genotoxic and mutagenic effects of sewage sludge on Allium cepa

The objective of this study was to ascertain the cytotoxic, genotoxic and mutagenic potential of sewage sludge using Allium cepa bioassay. Solubilized and crude sludge from two sewage treatment stations (STSs), herein named JM and M, were tested. In addition, sanitized, crude and solubilized sludge were also analyzed from STS M. The treatments showed positive response to phytotoxicity, cytotoxicity, genotoxicity and/or mutagenicity. Despite negative results for MN F1 (micronuclei counted in F1 root cells, derived from meristematic cells), the monitoring of genotoxic and mutagenic activities of sewage sludge are recommended because in agricultural areas this residue is applied in large scale and continuously. Based on our results we advise caution in the use of sewage sludge in agricultural soils.

Cytotoxicity of zinc nanoparticles fabricated by Justicia adhatoda L. on root tips of Allium cepa L.--a model approach

Zinc nanoparticles were synthesized using aqueous leaf extract of Justicia adhatoda L. The characterization of nanoparticles was done by ultraviolet-visible (UV-vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and high-resolution transmission electron microscopy (HR-TEM). The characteristic absorption peak of the UV spectrum was recorded at 379 nm. The FTIR data revealed the possible biomolecules involved in bioreduction and capping of zinc nanoparticles for efficient stabilization. AFM and HR-TEM images have shown that the size of zinc nanoparticles ranges from 55 to 83 nm and they are spherical in shape. The biogenic zinc nanoparticles were evaluated for their toxic effect on mitotic chromosomes of Allium cepa as a model system. Experiments were conducted in triplicate to assay the effect of 25, 50, 75, and 100 % of zinc nanoparticles on mitotic chromosomes at an interval of 6 h duration for 24 h. The investigation revealed that the mitotic index (MI) was decreased with increased concentration of zinc nanoparticles and exposure duration. The results revealed that zinc nanoparticles have induced abnormalities like anaphase bridge formation, diagonal anaphase, C-metaphase, sticky metaphase, laggards, and sticky anaphase at different percentages and times of exposure. It is evident from the observation that mitotic cell division becomes abortive at 100 % treatment of zinc nanoparticles.

Mutagenicity and genotoxicity of drinking water in Guelma region, Algeria

In this study, a battery of genotoxicity assays for monitoring drinking water was performed to assess the quality of the water resulting from the treatment plants. Five different types of samples were collected: raw water (P1), treated after pre-chlorination (P2), treated after decantation (P3), treated post-chlorination (P4), and consumers' taps (P5-P12). This study aims to evaluate the formation/occurrence of mutagenic and/or genotoxic compounds in surface drinking waters treated with chlorine disinfectant, during four seasonal experiments: summer, autumn, winter, and spring between 2012 and 2013 by bacterial reverse mutation assay in both Salmonella typhimurium TA98 and TA100 strains with or without metabolic activation system (S9 mix) and Allium cepa root meristematic cells, respectively. All of water samples, except at P1, P2, and P5 in summer; P1 in autumn; and P1 and P3-P12 in spring without S9 mix, and at P1 and P2 in summer and P6 and P8-P12 in spring with S9 mix, were found to be mutagenic in S. typhimurium TA98. However, only P11 and P12 in winter were found to be mutagenic for TA100 without S9 mix. The tested preparations in Allium anaphase-telophase test revealed a significant decrease in mitotic index (MI) and a simultaneous increase in chromosome aberrations (CAs) compared to the control. The bridge, stickiness, vagrant chromosomes, and disturbed chromosome aberrations were observed in anaphase-telophase cells. Physicochemical analysis, trihalomethanes (THMs), romoform (CHBr3), chloroform (CHCl3), bromodichloromethane (CHBrCl2), and dibromochloromethane (CHBr2Cl) levels in water samples were also determined. The results show also that this short-term battery tests are applicable in the routine monitoring of drinking water quality before and after distribution.

Allium cepa L. as a bioindicator to measure cytotoxicity of surface water of the Quatorze River, located in Francisco Beltrão, Paraná, Brazil

Due to an increase in water consumption in the industrial sector and within the Brazilian population, surface water that receives wastewater from industries, domestic sewage, agricultural industries, and sewage treatment stations can pollute water bodies when not properly treated. The water quality has been linked to catchment characteristics and intensity of agricultural activities. Thus, the aim of this study was to monitor the cytotoxic potential of the water of the Quatorze River, located in the town of Francisco Beltrão, Paraná, Brazil, along its route in the rural area, using the root meristematic cells of Allium cepa L. as a bioindicator. The results showed that the water at points 2, 3, and 4 were not cytotoxic because the rates of A. cepa cell division were unaltered. Point 1 had presented a mitotic index that was statistically larger than the negative control, indicating that this water contained substances with mitogenic capacity, as demonstrated by elevated values in chemical oxygen demand (COD) and biochemical oxygen demand (BOD). However, the mitotic index values decreased along the route of the river (point 1 to point 4), possibly indicating a mechanism of self-purification, despite having received other sources of pollution. Thus, the results of this study show that the water of the Quatorze River should undergo periodic environmental monitoring at different times of the year, including cytotoxicity analysis, to evaluate the principal sources of contamination to maintain the quality of the river water and, consequently, to maintain human health and equilibrium of the entire ecosystem.

Avaliação in situ da genotoxicidade de triazinas utilizando o bioensaio Trad-SHM de Tradescantia clone 4430

O bioensaio da mutação do pelo estaminal de Tradescantia clone 4430 (Trad-SHM) foi utilizado para avaliar a genotoxicidade de um herbicida composto por triazinas (atrazina e simazina) após exposição in situ. Trinta vasos da planta foram expostos durante a aplicação do herbicida (grupo teste) mantendo-se um grupo controle em casa de vegetação. A genotoxicidade foi expressa em termos de eventos mutantes pink (EMP) e a análise dos dados foi realizada por meio do teste t de Student em oito dias de avaliação (C8D = controle 8 dias; T8D = teste 8 dias) e no dia de pico (CPD = controle dia de pico; TPD = teste dia de pico). A exposição ao herbicida causou um número significativamente maior de EMP no grupo teste (T8D = 2,27; TPD = 4,69) do que no controle (C8D = 0,71; CPD = 0,62), demonstrando a existência de risco genotóxico associado ao uso das triazinas, sendo o bioensaio Trad-SHM uma eficiente ferramenta para avaliar o potencial genotóxico destes contaminantes ambientais causadores de efeitos adversos à saúde humana.

Investigation of organic pollutants in wastewater-irrigated soil and its DNA damage and oxidative damage on mice

This work aimed to determine the DNA and oxidative damage on mice by mixtures of organic contaminants in wastewater-irrigated soil, in order to assess their usefulness as markers for this kind of pollution. Wastewater-irrigated soil samples in the vicinity of an industrial area in Tangshan, China were collected, and soil irrigated by underground water satisfying drinking water standards was used as control group. Organic pollutants were extracted from the soil using ultrasonic oscillation, and analyzed by gas chromatography-mass spectrometry (GC-MS). Meanwhile, DNA damage on mice was determined by the Comet assay after oral gavage with the extracts, and changes in total superoxide dismutase (T-SOD) activity, glutathione peroxidase glutathione, GSH peroxidase (GSH-P(X)) activity and malondialdehyde content in serum of mice were investigated. The number of categories and concentrations of organic compounds in the wastewater-irrigated soil is more than those in groundwater-irrigated soil, as identified by the GC-MS. The toxicity test of mice showed that compared with reagent control group, the activities of T-SOD and GSH-P(X) decreased; the tailing rate of peripheral blood lymphocyte of mice increased and was more than that of the control group. This shows that mammalian toxicity end points can be used to determine the joint toxicity of organic pollutants in soil. When there is no means to identify each and every pollutant in soil, it is feasible to evaluate the combined effects of various pollutants to determine the extent to which the soil is polluted.

Clastogenicity of landfarming soil treated with sugar cane vinasse

The addition of nutrients and/or soil bulking agents is used in bioremediation to increase microbial activity in contaminated soils. For this purpose, some studies have assessed the effectiveness of vinasse in the bioremediation of soils contaminated with petroleum waste. The present study was aimed at investigating the clastogenic/aneugenic potential of landfarming soil from a petroleum refinery before and after addition of sugar cane vinasse using the Allium cepa bioassay. Our results show that the addition of sugar cane vinasse to landfarming soil potentiates the clastogenic effects of the latter probably due the release of metals that were previously adsorbed into the organic matter. These metals may have interacted synergistically with petroleum hydrocarbons present in the landfarming soil treated with sugar cane vinasse. We recommend further tests to monitor the effects of sugar cane vinasse on soils contaminated with organic wastes.

A level change in mutagenicity of Japanese tap water over the past 12 yr

A relative comparison study of mutagenicity in Japanese tap water was conducted for 1993 and 2005 surveys. It intended to assess the effects of advanced water treatment installations to water works, improvement of raw water quality and improvement of residual HOCl concentration controlling. Sampling points (taps) were the same in both surveys. The results of 245 samples obtained by the Ames Salmonella mutagenicity test (Ames test) were analyzed. The Ames tests were conducted by using Salmonella typhimurium TA98 and TA100 strains with and without exogenous activation (S9). With the exception of TA100-S9, the other conditions needed no discussion as a factor in the mutagenicity level change. The average mutagenicity in 1993 and 2005 under the conditions of TA100-S9 were 2600 and 1100 net revertantL(-1), respectively. This indicated that the mutagenicity level of Japanese tap water decreased during the 12-yr period. Particularly a remarkable decrease in mutagenicity was observed in the water works where the advanced water treatments were installed during the 12-yr period. The advanced water treatments were effective in decreasing the mutagenicity of tap water. Mutagenicity also decreased in the water works with conventional water treatments; the improvement of residual HOCl concentration controlling was also considered to be effective in decreasing the mutagenicity of tap water.

Micronucleus assays with Tradescantia pollen tetrads: an update

Micronucleus (MN) assays with early pollen tetrad cells of Tradescantia (Trad-MN assays) are at present the most widely used bioassays with plants for the detection of genotoxins in the environment. So far, ∼ 160 chemicals have been tested and ∼ 100 articles that concern complex environmental mixtures were published. This article summarises the results of Trad-MN studies, which have been carried out during the last 15 years with individual compounds and investigations concerning the pollution of environmental compartments (soil, water and air). The evaluation shows that the effects of certain genotoxins such as heavy metals, radionuclides, pesticides and air pollutants can be easily detected with this test. Comparisons with results obtained in MN studies with mitotic (root tip) cells indicate that meiotic tetrad cells are in general more sensitive. Important issues for future research concern the evaluation of the suitability of wildlife Tradescantia species that are sometimes used instead of specific clones (such as #4430 for which standardised protocols have been developed) as well as the assessment of the predictive value of Trad-MN results in regard to the prediction of cancer hazards in humans and adverse effects at the ecosystem level. The fact that the genotoxic effects of certain compound such as metals, which can be detected with plant bioassays, in particular with the Trad-MN assay but not in other commonly used bioassays (e.g. in bacterial tests) makes them an essential element in the batteries for environmental monitoring.

Environmental mutagenicity and toxicity caused by sodium metabisulfite in sea shrimp harvesting in Piauí, Brazil

Sodium metabisulfite is used in marine shrimp harvesting to prevent the occurrence of black spots. Shrimps are soaked in a sodium metabisulfite solution in ice, which is disposed of in sewages that run into marine canals, creating an environmental hazard. This study evaluates the toxicity and mutagenicity caused by sodium metabisulfite in sea waters and sediments collected in a shrimp farm in Cajueiro da Praia (Luis Correia), state of Piauí, Brazil, using the Allium cepa assay. Water and sediment samples were collected in the dry and in the rainy seasons, in three sites: upstream the shrimp farm (Site 1), at the point sodium metabisulfite is discharged (Site 2), and 100 m downstream the farm (Site 3). Three sample dilutions were used (50%, 25% and 10%) for all samples. A negative control (well water) and a positive control (copper sulfate 0.0006 mg mL⁻¹) were used in each experiment. At the end of the 72-h exposure period, onion roots were measured and removed. Mutagenicity analysis included the determination of mitotic index, chromosomal aberrations and the detection of micronuclei; analysis of root size and mitotic index were used as an index of toxicity. The A. cepa assay revealed that the water and sediments samples collected in the Piauí coast contaminated with sodium metabisulfite induce toxicity. The results demonstrate that the assay may be used as a regular tool in the analysis of water parameters in shrimp farms in the coast of Piauí state, and in strategies to preserve the region's marine ecosystem.

Thiocyclam does not induce structural chromosome aberrations in human lymphocytes in vitro

Thiocyclam (trade name Evisect) is a broad-spectrum nereistoxin analogue insecticide used widely for agricultural applications. The aim of this investigation was to determine its genotoxic effects in the chromosome aberration (CA) test and determining of mitotic index (MI), using lymphocytes from peripheral blood samples of healthy human donors. A negative and a positive control (MMC) were also included. Chromosomal analyses of the metaphase plates of the samples treated with 14 different concentrations (from 0.1 to 120 μg/ml) of thiocyclam, indicating the lack effect on chromosomes. Thus thiocyclam is not genotoxic but highly toxic on cell proliferation in human lymphocytes.

Bioavailability of xenobiotics in the soil environment

It is often presumed that all chemicals in soil are available to microorganisms, plant roots, and soil fauna via dermal exposure. Subsequent bioaccumulation through the food chain may then result in exposure to higher organisms. Using the presumption of total availability, national governments reduce environmental threshold levels of regulated chemicals by increasing guideline safety margins. However, evidence shows that chemical residues in the soil environment are not always bioavailable. Hence, actual chemical exposure levels of biota are much less than concentrations present in soil would suggest. Because "bioavailability" conveys meaning that combines implications of chemical sol persistency, efficacy, and toxicity, insights on the magnitude of a chemicals soil bioavailability is valuable. however, soil bioavailability of chemicals is a complex topic, and is affected by chemical properties, soil properties, species exposed, climate, and interaction processes. In this review, the state-of-art scientific basis for bioavailability is addressed. Key points covered include: definition, factors affecting bioavailability, equations governing key transport and distributive kinetics, and primary methods for estimating bioavailability. Primary transport mechanisms in living organisms, critical to an understanding of bioavailability, also presage the review. Transport of lipophilic chemicals occurs mainly by passive diffusion for all microorganisms, plants, and soil fauna. Therefore, the distribution of a chemical between organisms and soil (bioavailable proportion) follows partition equilibrium theory. However, a chemical's bioavailability does not always follow partition equilibrium theory because of other interactions with soil, such as soil sorption, hysteretic desorption, effects of surfactants in pore water, formation of "bound residue", etc. Bioassays for estimating chemical bioavailability have been introduced with several targeted endpoints: microbial degradation, uptake by higher plants and soil fauna, and toxicity to organisms. However, there bioassays are often time consuming and laborious. Thus, mild extraction methods have been employed to estimate bioavailability of chemicals. Mild methods include sequential extraction using alcohols, hexane/water, supercritical fluids (carbon dioxide), aqueous hydroxypropyl-beta-cyclodextrin extraction, polymeric TENAX beads extraction, and poly(dimethylsiloxane)-coated solid-phase microextraction. It should be noted that mild extraction methods may predict bioavailability at the moment when measurements are carried out, but not the changes in bioavailability that may occur over time. Simulation models are needed to estimate better bioavailability as a function of exposure time. In the past, models have progressed significantly by addressing each group of organisms separately: microbial degradation, plant uptake via evapotranspiration processes, and uptake of soil fauna in their habitat. This approach has been used primarily because of wide differences in the physiology and behaviors of such disparate organisms. However, improvement of models is badly needed, Particularly to describe uptake processes by plant and animals that impinge on bioavailability. Although models are required to describe all important factors that may affect chemical bioavailability to individual organisms over time (e.g., sorption/desorption to soil/sediment, volatilization, dissolution, aging, "bound residue" formation, biodegradation, etc.), these models should be simplified, when possible, to limit the number of parameters to the practical minimum. Although significant scientific progress has been made in understanding the complexities in specific methodologies dedicated to determining bioavailability, no method has yet emerged to characterized bioavailability across a wide range of chemicals, organisms, and soils/sediments. The primary aim in studying bioavailability is to define options for addressing bioremediation or environmental toxicity (risk assessment), and that is unlikely to change. Because of its importance in estimating research is needed to more comprehensively address the key environmental issue of "bioavailability of chemicals in soil/sediment."

The Allium cepa bioassay to evaluate landfarming soil, before and after the addition of rice hulls to accelerate organic pollutants biodegradation

Landfarming is a soil bioremediation technology practiced by oil refineries in order to reduce or eliminate hydrocarbons from petroleum sludge. The goal of the current study was to use Allium cepa bioassay to assess landfarming and landfarming with rice hulls amendment before and after hydrocarbons biodegradation assay in the laboratory. Three cytogenetic endpoints were used: mitotic and chromosome abnormalities (MCA), micronucleus (MN) and nuclear buds (NB). Landfarming presented 13.5 g/kg of total petroleum hydrocarbons (TPHs) and caused strong clastogenic and mutagenic effects (p<0.05) in A. cepa. After 108 days of biodegradation, the landfarming reached the rate of 26.30 mmol of CO(2) released, the concentration of TPHs decreased by 27% and there was significant reduction in MCA, MN and NB. Landfarming treated with rice hulls had the highest release of CO(2), 110.9 mmol, associated with a remarkable reduction in TPHs concentration, 59%, and had the highest decrease in MCA, MN and NB (p>0.05). Our findings showed that the use of rice hulls accelerated the biodegradation efficacy of landfarming and reduced their clastogenicity, indicating that supplementary treatments are important to improve the efficiency of bioremediation processes.

Evaluation of genotoxicity of coal fly ash in Allium cepa root cells by combining comet assay with the Allium test

Fly ash is a by-product of coal-fired electricity generation plants. Its utilization and disposal is of utmost importance. Using onion (Allium cepa) root tip system, the present study was carried out to evaluate the potential toxic and genotoxic effects of fly ash, collected from a thermal power plant in West Bengal, India. Prior to testing, the collected fly ash sample was mixed with sand in different proportions. Allium bulbs were allowed to germinate directly in fly ash and after five days the germinating roots were processed for the Allium test. Additionally, the Allium test was adapted for detecting DNA damage through comet assay. The results from the Allium test indicate that fly ash at 100% concentration inhibits root growth and mitotic indices; induces binucleated cells as a function of the proportion, but is not toxic at very low concentration. In the comet assay, a statistical increase for DNA strand breaks was found only at higher concentrations. The sample was analyzed by flame atomic absorption spectrometer for Zn, Pb, Cu, Ni, Cd and As, whose presence could partly be responsible for the toxicity of fly ash. The study concludes that the classical Allium test can give a more comprehensive data when done in combination with the comet assay, which is faster, simpler and independent of mitosis. Also when fly ash is used for other purposes in combination with soils, it should be judiciously used at very low concentrations in order to protect the ecosystem health from any potential adverse effects.

Herbicide effects on freshwater benthic diatoms: induction of nucleus alterations and silica cell wall abnormalities

Benthic diatoms are well known bio-indicators of river pollution by nutrients (nitrogen and phosphorus). Biological indexes, based on diatom sensitivity for non-toxic pollution, have been developed to assess the water quality. Nevertheless, they are not reliable tools to detect pollution by pesticides. Many authors have suggested that toxic agents, like pesticides, induce abnormalities of the diatom cell wall (frustule). High abnormal frustule abundances have been reported in natural diatom communities sampled in streams contaminated by pesticides. However, no direct link was found between the abundances of abnormal frustules in these communities and the pesticide concentrations in stream water. In the present study, a freshwater benthic diatom community, isolated from natural biofilm and cultured under controlled conditions, was treated with a known genotoxic herbicide, maleic hydrazide (MH). Cells were exposed to three concentrations of MH (5x10(-6), 10(-6), 10(-7)M) for 6h followed by a 24h-recovery time. After MH treatments, nucleus alterations were observed: abnormal nucleus location, micronucleus, multinuclear cell or disruption of the nuclear membrane. A dose-dependent increase of nuclear alterations was observed. The difference between the control (9.65 nuclear alterations per 1000 cells observed (9.65 per thousand), S.D.=4.23) and the highest concentrations (29.40 per thousand, S.D.=8.49 for 10(-6)M and 35.96 per thousand, S.D.=3.71 for 5x10(-6)M) was statistically significant (Tukey test, P<0.05). Diatoms also exhibited frustules with deformed morphology and abnormal ornamentation. Significantly increased abundances of abnormal frustules were observed for the highest concentrations (10(-6) and 5x10(-6)M; Tukey test, P<0.05). These two parameters tended to increase together (Pearson correlation=0.702, P<0.05). The results suggest that the induction of abnormal frustules could be associated with the genotoxic effects of MH. The alterations observed could be related to the effects of MH on the synthesis of the proteins involved in frustule formation or in the regulation of the cytoskeleton of the diatom cells.

Comparative genotoxicity evaluation of imidazolinone herbicides in somatic cells of Drosophila melanogaster

In the present study, five analogous herbicides, namely Imazapyr (IMZR), Imazapic (IMZC), Imazethapyr (IMZT), Imazamox (IMZX) and Imazaquin (IMZQ), were evaluated for genotoxicity (mutagenic and recombinagenic activity) in the wing somatic mutation and recombination test (SMART) of Drosophila melanogaster. They are classified as imidazolinone (IMI) herbicides and their mode of action is to inhibit acetohydroxyacid synthase (AHAS), an enzyme involved in the biosynthesis of the amino acids leucine, isoleucine and valine. Two crosses were used: the standard (ST) cross and the high bioactivation (HB) cross. The latter is characterized by high levels of cytochrome P450 conferring increased sensitivity to promutagens and procarcinogens. Three-day-old larvae were exposed by chronic feeding (48 h) to four different concentrations of these herbicides (2.5, 5.0, 10.0 or 20.0 mM). For the evaluation of genotoxic effects, the frequencies of spots per individual in the treated series were compared to the concurrent negative control series (ultrapure water). Imazapyr, Imazapic and Imazethapyr gave negative results with both crosses of the wing spot test. In the ST cross, Imazamox showed positive results only for large single spots (20.0 mM IMZX) and weak positive results for total spots (10.0 and 20.0 mM IMZX), while Imazaquin showed positive results only for large single spots (5.0 and 20.0mM IMZQ) and a weak positive result for total spots (20.0 mM IMZQ). These positive results are mainly due to induced recombination and to a minor extent to mutations. In the HB cross, only Imazamox (5.0 mM IMZX) showed a weak positive result for small single spots. The positive control urethane, a promutagen, caused an increase in the number of all types of spots in both crosses. In conclusion, the results of chronic treatments performed at high doses (toxicity was observed at higher doses) shows the existence of a genotoxic risk for IMZX and IMZQ exposure under these experimental conditions, and indicate the need for further research to delineate the exact mechanisms involved.

Genotoxicity assessment of soils from wastewater irrigation areas and bioremediation sites using the Vicia faba root tip micronucleus assay

Genotoxicity potential of soils taken from wastewater irrigation areas and bioremediation sites was assessed using the Vicia faba root tip micronucleus assay. Twenty five soils were tested, of which 8 were uncontaminated soils and taken as the control to examine the influence of soil properties; 6 soils were obtained from paddy rice fields with a history of long-term wastewater irrigation; 6 soils were obtained from bioremediation sites to examine effects of bioremediation; and 5 PAH-contaminated soils were used to examine methodological effects between direct soil exposure and exposure to aqueous soil extracts on micronuclei (MN) frequency ( per thousand) in the V. faba root tips. Results indicate that soil properties had no significant influences on MN frequencies (p > 0.05) when soil pH varied between 3.4 to 7.6 and organic carbon between 0.4% and 18.6%. The MN frequency measured in these control soils ranged from 1.6 per thousand to 5.8 per thousand. MN frequencies in soils from wastewater irrigation areas showed 2- to 48-fold increase as compared with the control. Soils from bioremediation sites showed a mixed picture: MN frequencies in some soils decreased after bioremediation, possibly due to detoxification; whereas in other cases remediated soils induced higher MN frequencies, suggesting that genotoxic substances might be produced during bioremediation. Exposure to aqueous soil extracts gave a higher MN frequency than direct exposure in 3 soils. However, the opposite was observed in the other two soils, suggesting that both exposure routes should be tested in case of negative results from one route. Data obtained from this study indicate that the MN assay is a sensitive assay suitable for evaluating genotoxicity of soils.

Use of plant genotoxicity bioassay for the evaluation of efficiency of algal biofilters in bioremediation of toxic industrial effluent

The toxicity and efficacy of an algal-based bioremediation technology were assessed through bioassays for ecological risk of contaminated industrial effluents. The algal bioremoval of heavy metals was evaluated using an in vitro approach. Phytogenotoxicity tests were conducted with Allium cepa and Vicia faba plants to evaluate the genotoxicity of the industrial effluents before and after treatment with different kinds of algal biofilters (BF). Root cells were exposed for 24 h to different dilutions of both raw and treated effluent of a chemical fertilizer factory. Three cytogenetic endpoints were used to assess the mutagenic potencies of the industrial effluent: mitotic inhibition, mitotic chromosome aberrations, and nuclear irregularities in interphase cells. Before algal treatment, the industrial effluent caused strong genotoxic effects represented by severe inhibition in mitotic activity of meristematic cells and high frequency of both chromosome and nucleus abnormalities. After algal treatment, the cytotoxic effects of 30% and 60% concentrations of the treated effluent were comparable to those of 5% and 10% concentrations before treatment, respectively, and the frequency of both chromosome and nuclear abnormalities declined by approximately 50%. Statistical analysis of the data indicates a significant reduction in genotoxicity associated with a remarkable reduction in heavy metal concentrations after bioremediation by algal BF. The Allium and Vicia genotoxicity approach was effective in monitoring bioremediated effluent for toxicity.

Polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and heavy metals (HMs) as well as their genotoxicity in soil after long-term wastewater irrigation

A study was carried out on the residue level of major concern pollutants (PAHs, PCBs and HMs) and the assessment of their genotoxicity in soils obtained from Shenyang, northeast of China which had been subjected to wastewater irrigation for more than 40 years. Topsoils (0-20cm) in paddy fields were sampled along the upper, middle and lower reaches of the wastewater disposal channel. Sixteen USEPA PAHs were determined by High Performance Liquid Chromatography (HPLC) with fluorescence detector, eight PCBs were detected by Gas Chromatography (GC) with electron capture detector, and six heavy metals (Cd, Cu, Pb, Zn, Ni, and Cr) were measured by Atomic Absorption Spectrophotometer (AAS). The genotoxicity effect of soils was examined by Vicia faba micronucleus (MN) test. Archived soils that had undergone a similar history of wastewater irrigation provided by Technical University of Berlin, Germany were subjected to analysis of the above pollutants and Vicia faba/MN test for comparison. Results indicated elevated residues of the studied pollutants (PAHs, especially benzo (a) pyrene, the eight PCB congeners and heavy metals) in both tested and archived soils. The MN frequencies were 2.2-48.4 times higher compared with the control. However, there was no correlation between the MN frequencies and the concentration of pollutants detected. This investigation suggested a potential ecological risk even with a lower level of residual pollutants in soil matrix after long-term wastewater irrigation.

Influence of extraction parameters on the mutagenicity of soil samples

The aim of this study was to investigate the influence of four extraction parameters (type of solvent, temperature, duration of extraction, and soil mass/solvent volume ratio) on the mutagenicity of soil extracts. Four urban soil samples were submitted to the micro-method adaptation of the Ames test on Salmonella typhimurium according to the following sequence: identification of the most sensitive strain (TA98 or TA100), the best solvent(s), the optimum extraction temperature and extraction time, and finally the optimal soil/solvent ratio. Extraction was thus performed using eight different solvents (distilled water, dichloromethane, acetonitrile, acetone, cyclohexane, methanol, hexane, or ethanol), two temperatures (room temperature or 37 degrees C), two durations (4 or 24 h), and two soil mass/solvent volume ratios (1:2 or 1:10). The results show that strain TA98 was more sensitive than strain TA100, and the observed mutagenicity was expressed as number of TA98 revertants per mg of soil equivalent. No mutagenicity was induced by the distilled water extracts, whereas most of the organic solvent extracts induced a significant mutagenic response. A dichloromethane/acetone mixture appeared to be the best compromise for extraction of mutagens from the urban soils tested. Moreover, the present study showed that a higher mutagenic activity was generally obtained with a temperature of 37 degrees C (compared to room temperature), with an extraction time of 24 h (compared to 4 h), and with a soil mass/solvent volume ratio of 1:10 (compared to 1:2).

Mutagens in contaminated soil: a review

The intentional and accidental discharges of toxic pollutants into the lithosphere results in soil contamination. In some cases (e.g., wood preserving wastes, coal-tar, airborne combustion by-products), the contaminated soil constitutes a genotoxic hazard. This work is a comprehensive review of published information on soil mutagenicity. In total, 1312 assessments of genotoxic activity from 118 works were examined. The majority of the assessments (37.6%) employed the Salmonella mutagenicity test with strains TA98 and/or TA100. An additional 37.6% of the assessments employed a variety of plant species (e.g., Tradescantia clone 4430, Vicia faba, Zea mays, Allium cepa) to assess mutagenic activity. The compiled data on Salmonella mutagenicity indicates significant differences (p<0.0001) in mean potency (revertents per gram dry weight) between industrial, urban, and rural/agricultural sites. Additional analyses showed significant empirical relationships between S9-activated TA98 mutagenicity and soil polycyclic aromatic hydrocarbon (PAH) concentration (r2=0.19 to 0.25, p<0.0001), and between direct-acting TA98 mutagenicity and soil dinitropyrene (DNP) concentration (r2=0.87, p<0.0001). The plant assay data revealed excellent response ranges and significant differences between heavily contaminated, industrial, rural/agricultural, and reference sites, for the anaphase aberration in Allium cepa (direct soil contact) and the waxy locus mutation assay in Zea mays (direct soil contact). The Tradescantia assays appeared to be less responsive, particularly for exposures to aqueous soil leachates. Additional data analyses showed empirical relationships between anaphase aberrations in Allium, or mutations in Arabidopsis, and the 137Cs contamination of soils. Induction of micronuclei in Tradescantia is significantly related to the soil concentration of several metals (e.g., Sb, Cu, Cr, As, Pb, Cd, Ni, Zn). Review of published remediation exercises showed effective removal of genotoxic petrochemical wastes within one year. Remediation of more refractory genotoxic material (e.g., explosives, creosote) frequently showed increases in mutagenic hazard that remained for extended periods. Despite substantial contamination and mutagenic hazards, the risk of adverse effect (e.g., mutation, cancer) in humans or terrestrial biota is difficult to quantify.

Clastogenicity of atrazine assessed with the Allium cepa test

Atrazine is classified as a restricted use pesticide and it is currently included in an international revision program for re-evaluating the human and ecological (non-human populations) health risks associated with its release into the environment. The present study was undertaken to add new data on the genotoxic potential of atrazine using the Allium cepa chromosome aberration test. The test concentrations were based on the Maximum Contaminant Levels in water intended for human consumption set by European and US regulations. Atrazine produced a concentration-related increase in the number of total somatic chromosome aberrations, although this increase was statistically significant (p<0.05) only at the highest test concentration (5 microg/L). Analysis of the categories of structural chromosome damage indicated that breaks were the predominant lesion induced; the percent of cells per bulb with breaks also increased in a concentration-related manner, and the increase was statistically significant at the two highest test concentrations (1 and 5 microg/L) (p<0.05). The Allium cepa plant assay detected the clastogenicity of atrazine at concentrations that are likely to be encountered in water, a common site of atrazine contamination.

Genotoxic hazards of long-term application of wastewater on agricultural soil

In the city of Aligarh (India), wastewater coming from both industrial and domestic sources and without any treatment is used to irrigate the agricultural crops. This practice has been polluting the soil, and the pollutants could possibly reach the food chain. For the above reason, soil irrigated with wastewater was sampled and monitored for the presence of genotoxic agents using three biological assays namely Ames Salmonella/mammalian microsome test, survival of SOS defective E. coli K-12 mutants and bacteriophage lambda systems. Extracts from soils were prepared using different organic solvents, i.e. methanol, acetonitrile and acetone. TA98 was found to be most sensitive strain to all the soil extracts. A significant decline in the survival of DNA repair defective E. coli K-12 mutants as compared to their isogenic wild-type counterparts were observed when treated with soil extracts. PolA was found to be the most sensitive strain. A remarkable decline in the plaque forming units was also observed when tested with the soil extracts. Extracts of soil that has been irrigated with ground water were also tested by the above three biological assays to compare the results.

Seasonal variation in the frequency of abnormal anaphases and mitotic index values in wild populations of herb-Paris (Paris quadrifolia L., Trilliaceae): implications for genetic monitoring

The main aim of our study was to investigate seasonal variation in the frequency of abnormal anaphases and mitotic index values in wild populations of herb-Paris (Paris quadrifolia L., Trilliaceae). Plant material was collected in the year 2000 in Norway and in the year 2001 in Lithuania. There was statistically significant variation in the mitotic index values (chi(2)=1087.9, d.f.=16, P<0.0001) with the highest values during the active growth period in May and the lowest values at the end of vegetation period in September. Seasonal variation in the frequency of abnormal anaphases was statistically significant as well (chi(2)=28.23, d.f.=16, P=0.0297). The most frequent type of anaphase abnormality was vagrant chromosomes (64.2%) followed by bridges (28.6%), fragments (3.6%), sticky chromosomes (2.4%) and multipolar anaphases (1.2%). During the fieldwork, quite deep late frosts occurred. Mitotic index was lower in the plants collected immediately after the frosts or 1 week later than in the plants sampled before the frosts (52+/-13 and 123+/-15, respectively, P=0.0014). On the contrary, frequency of abnormal anaphases was statistically significantly elevated (P=0.0082) in plants after the frosts (6.35+/-1.54%) when compared to plants before the frosts (2.49+/-0.56%). Our results clearly indicated significant variation in the mitotic index values and frequency of abnormal anaphases in the wild populations of herb-Paris during the growth season. This variation may be related to the physiological conditions of the analysed plants as well as to certain ecological factors.

Mutagenicity of ground water (in the bore-holes) in Ararat Valley (Armenia) detected by Trad-SHM bioassay

The genotoxicity of ground water from four bore-holes of different depths (40-120m) in the Ararat valley (Armenia) used both for drinking and irrigation was investigated. The frequency of recessive somatic mutations was determined using the Tradescantia-stamen-hair-mutation (Trad-SHM) test. The Tradescantia clone 02 was used. The pink mutation events (PMEs) were increased by 3.18-6.81-fold in comparison with the control depending both on the depth of subterranean water location and the increase of Na(+) ion concentration in these water samples. The peak frequency was found in water from the 40-45m depth. The deeper the bore-holes, the lower the mutagenicity of water and the concentration of Na(+) ions. Different types of mutant sector arrangements and their frequencies changed depending on the subterranean water depth.

Biomonitoring the genotoxicity of environmental factors with transgenic plants

All organisms must react to constantly changing surroundings. Environmental factors are thus powerful forces continuously shaping the genomes of all species. Induced genetic changes can be followed using a biomonitor - a living organism that reacts to a given compound in the environment. A vital but challenging task is identifying organisms with which to study the influence of changing environmental conditions. Plants are especially valuable biomonitors. Here, we describe the use of transgenic plant systems to evaluate the genotoxicity of chemical and radiological compounds. We evaluate the potential of further transgene-based systems for studying somatic and germ-line mutations.