The improved Allium/Vicia root tip micronucleus assay for clastogenicity of environmental pollutants

Evaluation of the genotoxic, mutagenic and oxidant stress potentials of municipal solid waste incinerator bottom ash leachates

Triplicate aqueous leachates of a municipal solid waste incineration bottom ash (MSWIBA) were produced according to a European standardised method. Leachates analysis showed relatively low concentrations (less than 1 mg.l(-1)) for four metals (iron, cadmium, lead and copper). No mutagenic activity was revealed after performing the Salmonella/microsome assay with and without microsomal activation. With the Vicia root tip micronucleus assay, a significant increase in micronucleated cells was observed between 3.4% and 100% leachate concentration. Significant and elevated antioxidant stress enzyme activities, e.g., superoxide dismutase (SOD), catalase (CAT), peroxidase (PER) and glutathione reductase (GR), were detected in Vicia root tissues even at the lowest tested leachate concentration (i.e., 0.3%), whereas this was not always the case in leaf tissues, which showed tissue specificity for the tested enzymes. At the lowest concentration (i.e., 0.3%), a higher increase was observed (respectively 197% and 45% compared to the control) for root glutathione reductase and peroxidase activities over those of other enzymes (superoxide dismutase and catalase). Our results suggest that MSWIBA aqueous leachates need to be formally tested with genotoxic sensitive tests before recycling and support the hypothesis that plant genotoxicity is related to the cellular production of reactive oxygen species (ROS).

Genotoxicity of municipal landfill leachate on root tips of Vicia faba

The genotoxicity of municipal landfill leachate was studied using the Vicia faba root-tip cytogenetic bioassay. Results show that landfill leachates collected in different seasons decreased the mitotic index (MI) and caused significant increases of micronucleus (MN) frequencies and anaphase aberration (AA) frequencies in a concentration-dependent manner (concentration expressed as 'chemical oxygen demand' measured by the method of potassium dichromate oxidation (COD(Cr))). In addition, a seasonal difference in genotoxicity induced by leachate was observed. The results confirm that leachate is a genotoxic agent in plant cells and imply that exposure to leachate in the aquatic environment may pose a potential genotoxic risk to organisms. The results also show that the V. faba cytogenetic bioassay is efficient, simple and reproducible in genotoxicity studies of leachate, and that there is a correlation between the genotoxicity and the chemical measurement (COD(Cr)) of leachate.

Induction of micronucleated cells in the shed skin of salamanders (Ambystoma sp.) treated with colchicine or cyclophosphamide

The micronucleus (MN) assay can be used to detect the genotoxic effects of chemical agents in virtually any cell that divides frequently. Salamanders (Ambystoma sp.) are amphibians that can be easily maintained and bred in the laboratory and spontaneously shed their skin every 2.5-4 days. In this present study, we have evaluated the usefulness of this shed skin for the MN assay. We exposed salamanders to different concentrations of both the aneugen colchicine (COL) and the clastogen cyclophosphamide (CP) and we determined the frequency of micronucleated cells (MNCs) in their sheds. Fragments of shed skin were placed on clean slides, fixed, stained, observed with a light microscope, and the number of MNCs was counted. The MNC frequency was increased significantly by all doses of COL and CP tested, administered either as single or repeated exposures. The presence of MNCs in the shed skin and the speed of sloughing lead us to propose that the sheds of Ambystoma sp., or other amphibians that slough their skin, are suitable alternative models for detecting genotoxic exposures relevant to aquatic environments.

Energy-dependent RBE of neutrons to induce micronuclei in root-tip cells of Allium cepa onion irradiated as dry dormant seeds and seedlings

The relative biological effectiveness (RBE) of various energy neutrons produced from a Schenkel-type accelerator at the Research Institute for Radiation Biology and Medicine, Hiroshima University (HIRRAC), compared with 60Co gamma-ray radiation was determined. The neutron radiations and gamma-ray radiation produced good linear changes in the frequency of micronuclei induced in the root-tip cells of Allium cepa onion irradiated as dry dormant seeds (seed assay) and seedlings (seedling assay) with varying radiation doses. Therefore the RBE for radiation-induced micronuclei can be calculated as the ratio of the slopes of the fitted linear dose response for the neutron radiations and the 60Co gamma-ray radiation. The RBE values by seed assay and seedling assay decreased to 174 +/- 7, from 216 +/- 9, and to 31.4 +/- 1.0, from 45.3 +/- 1.3 (one standard error), respectively, when neutron energies increased to 1.0 MeV, from 0.2 MeV, in the present study. Furthermore, the ratio of the micronucleus induction rates of seed assay to seedling assay by gamma-ray radiation was much lower than that by neutron radiations.

Genotoxicity of hydrated sulfur dioxide on root tips of Allium sativum and Vicia faba

Genotoxicity of sulfur dioxide (SO(2)) and its hydrates (bisulfite and sulfite) in human lymphocytes and other mammalian cells have been found earlier in our laboratory. In the present studies, we used Allium stavium and Vicia faba cytogenetic tests, which are the highly sensitive and simple plant bioassays. A mixture of sodium bisulfite and sodium sulfite (1:3), at various concentrations from 1 x 10(-4) to 2 x 10(-3)M was used for the treatment. Genotoxicity was expressed in terms of anaphase aberration (AA) frequencies in the Vicia-AA test and in terms of micronuclei (MCN) frequencies in both Vicia-MCN test and Alllium-MCN test. On average, the results showed a 1.7-3.9-fold increase of AA frequencies and a 3.5-4.5-fold increase of MCN frequencies in Vicia root tips as compared with the negative control. Similarly, results of Allium-MCN test also showed a significant increase in MCN frequencies in the treated samples. In addition, pycnotic cells (PNC) appeared in Allium root tips of treated groups. The frequencies of MCN, AA and PNC increased dose-dependently and the cell cycle delayed at the same time in bisulfite treated samples. Results of the present study suggest that the Vicia and Allium cytogenetic bioassays are efficient, simple and reproducible in genotoxicity studies of bisulfite.

Clastogenicity of pentachlorophenol, 2,4-D and butachlor evaluated by Allium root tip test

The meristematic mitotic cells of Allium cepa is an efficient cytogenetic material for chromosome aberration assay on environmental pollutants. For assessing genotoxicity of pentachlorophenol (PCP), 2,4-dichlorophenoxyacetic acid (2,4-D) and 2-chloro-2,6-diethyl-N-(butoxymethyl) acetanilide (butachlor), 50% effective concentration (EC(50)), c-mitosis, stickiness, chromosome breaks and mitotic index (MI) were used as endpoints of genotoxicity. EC(50) values for PCP and butachlor are 0.73 and 5.13 ppm, respectively. 2,4-D evidently induced morphological changes at higher concentrations. Some changes like crochet hooks, c-tumours and broken roots were unique to 2,4-D at 5-20 ppm. No such abnormalities were found in PCP and butachlor treated groups, however, root deteriorated and degenerated at higher concentrations (<3 ppm) in PCP. MI in 2,4-D showed a low average of 14.32% followed by PCP (19.53%), while in butachlor it was recorded 71.6%, which is near to the control value. All chemicals induced chromosome aberrations at statistically significant level. The highest chromosome aberration frequency (11.90%) was recorded in PCP at 3 ppm. Large number of c-mitotic anaphases indicated that butachlor acts as potent spindle inhibitor, whereas, breaks, bridges, stickiness and laggards were most frequently found in PCP showing that it is a potent clastogen.

Changes of reliability and efficiency of micronucleus bioassay in Vicia faba after exposure to metal contamination for several generations

Mitotic root micronucleus (MCN) frequency in Vicia faba as a bioassay, is primarily based on the extent of the sentinel Vicia response in terms of cytogenetic damage quantitatively or qualitatively to indicate the presence of mutagenic contaminants. This paper describes an investigation designed to assess changes in MCN frequencies of Vicia faba from three generation plants obtained, respectively from a reference site (RS) and a metal-contaminated experimental field (EF) in the bioassay of mutagenic Cd(2+) and NaN(3). The background value, dose-response to Cd(2+) and to NaN(3) in three generation (F(1), F(2) and F(3)) plants of the EF and the initial (F(0)) plants were determined in terms of MCN frequencies. With more generations of growing Vicia plants in the EF, a higher background value of MCN frequency, a lower slope value in the regression equation, a smaller ratio of MCN frequency between the control and treatment in the same generation and larger perturbation values were observed. This denotes that the decreased reliability and efficiency are represented in Vicia plants from the EF if the plants are used as sentinels in the bioassay of mutagenic Cd(2+) and NaN(3). It was concluded that the Vicia MCN bioassay should be used as an endpoint biomarker acceptable in biomonitoring environmental mutagens when the sentinel plants were collected from clean areas. Because no place is absolutely without pollutants, it is suggested that several seed stock centers should be established for providing sentinel Vicia if Vicia MCN bioassay is used as a biomarker to identify the global environmental status.

Vicia root-micronuclei assays on the clastogenicity of water samples from the Kui River near Xuzhou city, People's Republic of China

The Vicia root-micronucleus (VR-MCN) bioassay was used to determine the genotoxicity of water samples collected from the Kui River near Xuzhou city, China. Results show that all water samples induced elevated MCN frequencies over background. This indicates that the river water was polluted with genotoxic material. The source of pollutants in this river is discussed.

Assessment of the genotoxicity of contaminated soil with the Allium/Vicia-micronucleus and the Tradescantia-micronucleus assays

The present study concerns the genotoxicity of contaminated soil near Metz, France. Three plant bioassays, the Vicia faba (broad bean), the Allium cepa (white onion) and the Tradescantia (spiderwort) micronuclei tests were used to evaluate for genotoxicity. Two soil samples were tested: soil sample A (from an industrial waste site) and soil sample B (from a cokeworks waste site). Maleic hydrazide was used as the positive control. Aqueous extracts of the soil samples were used to treat the roots of Vicia and Allium, and plant cuttings of Tradescantia according to the standard protocol for these plant assays established by the International Program on Chemical Safety and the World Health Organization. The results of these tests showed differential sensitivity in the three different bioassays. Soil sample A was more toxic than soil sample B.

Clastogenicity of chromium contaminated soil samples evaluated by Vicia root-micronucleus assay

Chromium compounds have been known to be highly toxic in biological systems and to some individuals act as strong allergens. A chromium processing plant in Tianjin city has been abandoned for many years and the chromium residue has been dispersed into the nearby soil. This study was designed to detect the genotoxicity of contaminated soil samples collected at various distances of 100 to 1000 m from the source using the Vicia faba root micronucleus test. Water solutions extracted from the soil samples were used to treat the roots of the Vicia beans. Micronuclei frequencies observed from the root meristems were used to determine the degree of genotoxicity. Micronuclei frequencies of the contaminated soil samples show linear dose responses to chromium contents in the soil, which were inversely proportional to the distance from the source.

Vicia root micronucleus assay on the clastogenicity of water samples from the Xiaoqing River in Shandong Province of the People's Republic of China

Vicia root micronucleus assay was used to determine the clastogenicity of water samples from Xiaoqing River that passes through Jinan City. Positive results were obtained from eight water collecting sites. This indicates that the water in most areas of this river was polluted with industrial waste and municipal sewage. Results of this study proves that biomonitoring with Vicia root micronucleus test is an efficient way to assess the water quality of this river.

Pollution monitoring of three rivers passing through Fuzhou City, People's Republic of China

The Tradescantia-micronucleus (Trad-MCN) bioassay was used to determine the pollution levels of three rivers passing through Fuzhou city. Results indicate that all three rivers are polluted but at different levels. They are ranked as follows: Antai River > Baima River > Jinan River. Positive results were obtained when full strengths of the water samples were used to treat the plant cuttings when compared with the negative control (tap water) group. Negative responses were obtained when the Baima and Jinan river water was diluted to 50% but not for the sample from the Antai river. Micronuclei frequencies of the Antai river group were higher than the positive control using the Ping-Yang antibiotic drug (Huapei Drug Manufacturer) at 0.2 microg/ml concentration.

Detection of genotoxic effects of heavy metal contaminated soils with plant bioassays

Aim of the present study was the development of a bioassay which enables the detection of genotoxic effects of heavy metal contaminated soils. In the first part of the present study, the data base on metal effects in plant bioassays was extended. Four metal salts, namely Cr(VI)O3, Cr(III)Cl3, Ni(II)Cl2 and Sb(III)Cl3 were tested comparatively in MN tests with pollen tetrad cells of Tradescantia clone #4430 and in meristematic root tip cells of Vicia faba. With Cr6+ and Ni2+, clear-cut dose-effects were observed in a range between 0.75 and 10.0 mM, whereas this was not the case with Cr3+ (range tested 1.25-10 mM) and Sb3+ (range 0.30-5.25 mM). In Vicia, negative results were obtained with the four metal salts under all conditions of test. To compare the mutagenic potencies of the metals, the increases of the regression curves (k-values) were calculated, they indicate the number of MN induced per mM in 100 tetrad cells. The corresponding values for Cr6+ and Ni2+ are 0.87 and 1.05, respectively. It appears that the Tradescantia system is in particular sensitive towards those metal species which cause DNA damage in animals and man such as Cr6+, Cd2+, Ni2+, and Zn2+, whereas no clear positive results were obtained with less harmful metal ions such as Cu2+, Cr3+ or Sb3+. In the second part of the study, the mutagenic effects of four metal contaminated soils and two types of standardized leachates (pH 4.0 and pH 7.0) of these soils were tested in Tradescantia and in Vicia. In addition, chemical analyses were carried out to determine the metal concentrations in the soils and in the extracts. Two of the samples contained highly elevated levels of a number of metals (Zn, Pb, Cu, Cd, Sb, As), one soil came from the Central Austrian Alps and contained high As levels only. Direct exposure of the Tradescantia plants in the soils resulted in a drastic increase of the MN frequencies over the background. The lowest effect was seen with the Slovakian soil which contained in particular Sb and As (4.5-fold increase over the background), with the other soils, the induced frequencies were 11-15-fold over the control values. On the contrary, negative results were obtained upon exposure of Tradescantia cuttings in the leachates and upon implantation of germinated Vicia beans in the soils. The results of the present study indicate that Trad-MN assays with direct exposure of intact plants is an appropriate method which enables to detect genotoxic effects of metal contaminated soils in situ. This simple and fast biomonitoring assays might be a valuable supplement to analytical analyses of contaminated soils.

Mutagenicity (micronucleus test in Vicia faba root tips), polycyclic aromatic hydrocarbons and heavy metal content of sediments collected in Tiber river and its tributaries within the urban area of Rome

Sediments collected in Tiber river and in its main tributary water courses within the urban area of Rome were tested for mutagenicity by means of Vicia faba root tips micronucleus (MN) test. Representative samples were scored for micronucleus generating events (chromosome/chromatid loss and fragments) too. Sediments were assayed for content of the thirteen most important chemicals of polycyclic aromatic hydrocarbon (PAH) group and for some heavy metal ions (Cd, Cr, Cu, Ni, Pb, Zn). Samples were collected in four tributary rivers (Prima Porta, Acqua Traversa, Aniene and Magliana) just before their confluence with Tiber river and at different stations along the Tiber river itself upstream and downstream the sites of confluence of the sampled tributaries. All samples were collected in July 1992. An alarming level of mutagenicity was reached in most of the tested stations, with an effect comparable to an X-rays exposure up to 0.4 Gy. Chemical analysis showed that the total amount of identified PAHs ranged from 4.5 to 625.2 ng/g of dry matrix in the different stations and the total amount of heavy metals ranged from 130 to 570 ppm. Tiber mutagenicity is likely to be mainly due to local factors such as the confluence of a small polluted tributary rather than to large scale effect due to an upstream-downstream relationship.

The Allium cepa chromosome aberration test reliably measures genotoxicity of soils of inhabited areas in the Ukraine contaminated by the Chernobyl accident

The accident on the Chernobyl Nuclear Power Plant reactor IV in April 1986 led to the release of an enormous amount of radioactive material into the biosphere and to the formation of a complex pattern of nuclear contamination over a large area. As a consequence more than 5 million km2 of the soil in the Ukraine became contaminated with more than 1 Ci/km2 [1,2]. An assessment of the genetic consequences of the nuclear pollution is one of the most important problems. We applied the Allium cepa test to estimate the impact on plant chromosomes of nuclear pollution in the inhabited zones of the Ukraine. We tested soil from the obligatory resettlement zone (zone 2), where the mean density of pollution is 15-40 Ci/km2; zones of enhanced radiological control-zone 3, 5-15 Ci/km2 and zone 4, 1-5 Ci/km2. We found a dose-dependent increase in the fraction of aberrant mitoses from control values of 1.6 +/- 0.9% up to 23.8 +/- 5.0%, and a corresponding monotonous decrease of the mitotic index from 49.4 +/- 4.8% to a limiting value of 22.5 +/- 4.0% at pollution levels exceeding 35 Ci/km2 (activity of the soil samples exceeding 6000 Bq/kg, respectively). We observed a strong, significant correlation of 137Cs activity of soil samples with the percentage of chromosomal abnormalities, r = 0.97 (P < 0.05), and with the mitotic index, r = -0.93 (P < 0.05), in the roots of A. cepa, respectively. The results showed high toxicity and genotoxicity of radioactively polluted soils and confirmed the efficiency of the A. cepa test as a quick and inexpensive biological test for ecological and genetic risk assessment in the 'Chernobyl' zones.

Genotoxic effects of heavy metals: comparative investigation with plant bioassays

The potential use of micronucleus assays in plants for the detection of genotoxic effects of heavy-metal ions was investigated. Three different plant systems were comparatively investigated in micronucleus tests with Tradescantia pollen mother cells (Trad MCN) and micronucleus tests with meristematic root tip cells of Allium cepa and Vicia faba (Allium/ Vicia MCN). As3+, Pb2+, Cd2+, Zn2+ caused a dose-dependent increase of MCN frequencies in all three test systems. Cu2+ gave consistently negative responses in all three tests; Zn2+ caused only a moderate, statistically not significant increase of MCN frequencies in Vicia. The ranking of genotoxic potencies in all three tests was in the descending order: As3+ > Pb2+ > Cd2+ > Zn2+ Cu2+. In experiments with Tradescantia, induction of MCN was observed in a concentration range between 1 and 10 mM, whereas in tests with root tip cells, higher concentrations (10-1,000 mM) were required to show significant effects. Further increase of the exposure levels caused toxic effects (reduction of root growth), cell division delays, and a decrease of MCN frequencies. Comparisons by linear regression analyses indicated that the sensitivity of the three bioassays for heavy metals decreases in the order: Trad MCN > Vicia root MCN > Allium root MCN. In further experimental series, a soil sample which contained high concentrations of the five metals and a control soil were investigated. Aqueous soil extracts induced only weak effects in Trad MCN tests and no effects in the root tip assays, whereas cultivation of the plants in the soils resulted in a pronounced induction of MCN in the Tradescantia system and moderate effects in Vicia and Allium. In conclusion, the results of the study indicate that the Trad MCN assay detects the genotoxic effects of heavy metals and can be used for biomonitoring metal-contaminated soils.

Heavy metal content and mutagenic activity, evaluated by Vicia faba micronucleus test, of Tiber river sediments

Tiber river sediment samples, collected in October 1995, were tested for mutagenicity by the micronucleus test in Vicia faba root tips. Four stations were studied within the urban area of Rome: (1) Castel Giubileo, at the entry of the urban area; (2) Ponte Tor di Quinto, immediately after the confluence of the tributary river Aniene; (3) Ponte Sublicio, in the middle of the city; and (4) Ponte della Magliana, immediately outside Rome, 20 km from the sea. Since no significant increase in micronucleus frequency was observed in any of the tested stations compared to control (while in previous campaigns mutagenic activity was observed in some of the same stations), it can be assumed an interesting recovery from mutagenic pollution in the 2 last years. The samples were analysed for pH value, nitrogen, organic matter and carbonate content, and the concentration of some potentially mutagenic heavy metal ions (Zn, Cd, Ni, V, Cu) was assessed. In all samples, a concentration of heavy metals higher than unpolluted areas was observed. However, the alkaline pH measured should keep them as non-bioavailable elements.

Allium cepa anaphase-telophase root tip chromosome aberration assay on N-methyl-N-nitrosourea, maleic hydrazide, sodium azide, and ethyl methanesulfonate

The Allium anaphase-telophase assay was used to show genotoxicity of N-methyl-N-nitrosourea (MNU), maleic hydrazide (MH), sodium azide (NaN3) and ethyl methanesulfonate (EMS). All agents induced chromosome aberrations at statistically significant levels. The rank of the lowest doses with positive effect was as follows: NaN3 0.3 mg/l < MH 1 mg/l < MNU 41 mg/l < EMS 100 mg/l. The results were compared with results from other plant assays (Arabidopsis, Vicia, Tradescantia) and for MH and MNU the values were found to be within the same range, whereas the results in the Allium test for NaN3 and EMS were in a lower range than that found for the other plant assays. EMS and MMS (methyl methanesulfonate), two chemicals used as positive controls in mutagenicity testing, were compared in the Allium test, and MMS was found to be about ten times more potent in inducing chromosome aberrations than EMS. Recording of micronuclei in interphase cells showed that this endpoint does not give more information of clastogenicity than recording of chromosome aberrations in anaphase-telophase cells.

Vicia faba root tip micronucleus test on the mutagenicity of water-soluble contents of cigarette smoke

The possible mutagenicity of the water-soluble contents of cigarette smoke (WSCS) was evaluated by using the Vicia faba root tip micronucleus test. The results showed significant changes in micronucleus frequency which were caused by each different concentration of WSCS. This indicates that the Vicia faba root tip micronucleus test might be used as one kind of mutagenic detection method for cigarette smoke. A comparative evaluation on the mutagenicity of 10 brands of cigarettes was carried out. Results confirmed that various degrees of mutagenicity were found for all of the brand cigarettes, among them, Huaihai was the highest, while Camellia was the lowest. The micronucleus frequencies were reduced by adding tea polyphenol, nicotinamide adenine, vitamin C and sodium selenite to the WSCS. The results suggest that these added substances might reduce the genetic injury induced by cigarette smoke.