Juan Moretton

Genotoxicity of leachates from highly polluted lowland river sediments destined for disposal in landfill

The Matanza-Riachuelo is one of the most polluted rivers of Latin America. The complex chemical mixture of pollutants discharged into the river is accumulated in the river sediments. In this paper, Matanza-Riachuelo river sediment composition and genotoxicity were tested in order to develop a cost-effective, environmentally sound option for disposal and management of contaminated dredged materials. Sampling was performed in a rural area, in a solid waste dumpsite and also in an urban and industrial area. The concentrations of total heavy metals increased from the upper basin to the lower basin. The Ames Salmonella typhimurium test and the Saccharomyces cerevisiae D7 test were performed using toxicity characteristic leachate procedure (TCLP) leachates. The concentrations of copper, lead, and chromium in the leachates exceeded the guide levels for the protection of aquatic life. Low concentrations of organic chlorinated compounds were detected in the leachates. Genotoxic profiles were obtained by testing TCLP leachates from polluted sediment samples with Salmonella typhimurium, Saccharomyces cerevisiae D7, and water sediment suspension with Allium cepa test. No mutagenicity effects on Ames test were observed. Gene conversion and mitotic reversion in Saccharomyces cerevisiae D7 and chromosome aberration in Allium cepa were induced by the sediment samples. Results obtained suggest that dredged sediments could be classified as genotoxic hazardous waste.

Effects of six antibiotics and their binary mixtures on growth of Pseudokirchneriella subcapitata.

The effect of ampicillin (AMP), amoxicillin (AMX), cephalotin (CEP), ciprofloxacin (CPF), gentamycin (GEN), and vancomycin (VAN) have been examined individually and as binary mixtures, on a non-target aquatic organism, the green alga Pseudokichneriella subcapitata. The β-lactam antibiotics AMP and AMX were not toxic to the alga at concentrations up to 2000 mgl(-1) (less than 10% of algal growth inhibition), whereas the fluoroquinolone CPF, and the aminoglycoside GEN were the most toxic antibiotics, with an EC50=11.3 ± 0.7 mgl(-1) and 19.2 ± 0.5 mgl(-1), respectively. The cephalosporin CEP and the glycopeptide VAN were less toxic than the last two mentioned, showing an EC50>600 mgl(-1) and 724 ± 20 mgl(-1), respectively. The toxicological interactions of binary mixtures were predicted by the two classical models of additivity: concentration addition (CA) and independent action (IA), and compared to the experimentally determined toxicities over a range of concentrations between 1 and 50 mgl(-1). In all cases a clear synergistic effect was observed, showing that single compound toxicity data are not adequate for the prediction of aquatic toxicities of antibiotic mixtures. Risk assessment was performed by calculating the ratio between predicted environmental concentrations (PEC) and the predicted no effect concentration (PNEC). All the antibiotics tested, excepting GEN, have a potential ecological risk, taking into account the PEC of hospital effluents from Buenos Aires, Argentina. These risks increase when antibiotics are present in binary mixtures.

Case Method in the Teaching of Food Safety

One of the fundamental aims of education is the integration of theory and practice. The case method is a teaching strategy in which students must apply their knowledge to solve real-life situations. They have to analyze the case described and propose the best possible solution. Although the case may be written, the use of new information and communication technologies can develop the case plan in ways that would achieve greater realism and widen the possibilities for discussion. This paper describes our experience in implementing the case method to teach food safety in the Chair of Hygiene. At first this methodology was used to improve the teaching of good practices in food preparation, later practical work was implemented where small groups of students designed and carried out the microbiological analysis of suspected food. This practical work was presented online as a multimedia activity; students were given face-to-face and on-line tutoring. Evaluation was based both on students’ performance and on a survey they had to answer. More than 92% of students regarded the methodology used for the understanding of the unit as sound. Professors collaboration on providing guidance and multimedia presentation were also positively assessed. The bringing together of face-to-face and virtual tasks and small-group discussion of cases under professors guidance contributed to making good use of the positive aspects of this methodology in order to improve the understanding of problems which do not always have a single answer.

Ecotoxicological and Genotoxic Evaluation of Buenos Aires City (Argentina) Hospital Wastewater

Hospital wastewater (HWW) constitutes a potential risk to the ecosystems and human health due to the presence of toxic and genotoxic chemical compounds. In the present work we investigated toxicity and genotoxicity of wastewaters from the public hospital of Buenos Aires (Argentina). The effluent from the sewage treatment plant (STP) serving around 10 million inhabitants was also evaluated. The study was carried out between April and September 2012. Toxicity and genotoxicity assessment was performed using the green algae Pseudokirchneriella subcapitata and the Allium cepa test, respectively. Toxicity assay showed that 55% of the samples were toxic to the algae (%I of growth between 23.9 and 54.8). The A. cepa test showed that 40% of the samples were genotoxic. The analysis of chromosome aberrations (CA) and micronucleus (MN) showed no significant differences between days and significant differences between months. The sample from the STP was not genotoxic to A. cepa but toxic to the algae (%I = 41%), showing that sewage treatment was not totally effective. This study highlights the need for environmental control programs and the establishment of advanced and effective effluent treatment plants in the hospitals, which are merely dumping the wastewaters in the municipal sewerage system.

Genotoxic potential of waste waters from a leather industry

The genotoxic potential of tannery waste water was evaluated by means of the induction of gene conversion and point mutation in Saccharomyces cerevisiae D7 strain. Neither a toxic nor a genotoxic response was obtained after a 2 hr incubation of raw water samples with the strain. A dose-related increase in the induced gene conversion and mitotic reversion was obtained when dilutions of the raw effluent were incubated for 24 hr. Samples of the waste water were also passed through an XAD2 resin column. The column was sequentially eluted with ethyl ether, chloroform and methanol. The ether and methanol fractions showed a positive genotoxic response.

Polluted water concentrates: Induction of genetic alterations in Saccharomyces cerevisiae D7 strain

In a previous paper the authors showed that samples of raw water obtained from the Riachuelo (a heavily polluted watercourse) induced genetic effects in Saccharomyces cerevisiae D7 strain. In those tests the raw water samples were assayed within 24 hr and only the mutagenic activity of the non-volatile, water soluble constituents could be detected. The detection and quantitation of genetic toxicity in the organic water-insoluble fraction becomes much more difficult. This organic material consists of thousands of unidentified compounds in dilute mixtures which are not amenable to current analytical technology. Consequently, concentration of organic compounds is required before performance of biological tests. The development of analytical methods involving XAD resins for the isolation and identification of pesticides and other compounds led to the use of XAD resins in the concentration of organics in water. In the experiments reported here the genotoxic potential of XAD2 concentrates, obtained from samples of a heavily polluted stream, were evaluated by the induction of gene conversion and point mutation in Saccharomyces cerevisiae D7 strain.

La textura del suelo como factor regulador de la adsorción de Escherichia coli en una cuenca de la Pampa Ondulada (Argentina)

Resumen es: El aumento de la carga animal vacuna en la Pampa Ondulada asociado a areas fragiles supone un importante riesgo de contaminacion biologica. Dicha contami...

Detection of genotoxicants in a polluted watercourse by means of a yeast system

A strain of Saccharomyces cerevisiae that allows the simultaneous detection of mutation and genetic recombination was chosen as test organism for a biological assay in the monitoring of streams polluted by industrial effluents

Toxicity and genotoxicity assessment in sediments from the Matanza-Riachuelo river basin (Argentina) under the influence of heavy metals and organic contaminants

The aim of this study was to investigate the parameters of chemical extraction associated with the detection of toxicity and genotoxicity in sediment sample extracts. Quantitative analysis of metals and polycyclic aromatic hydrocarbons (PAHs), together with a battery of four bioassays, was performed in order to evaluate the extraction efficiency of inorganic and organic toxicants. The extracts were carried out using two inorganic solvents, two organic solvents and two extraction methodologies, making a total of five extracts. Two toxicity tests, the algal growth inhibition of Pseudokirchneriella subcapitata and the root elongation inhibition of Lactuca sativa, and two genotoxicity tests, the analysis of revertants of Salmonella typhimurium and the analysis of micronuclei and chromosomal aberrations in Allium cepa, were performed. According to the chemical analysis, the acidic solution extracted more heavy metal concentrations than distilled water, and dichloromethane extracted more but fewer concentrations of PAH compounds than methanol. Shaker extracts with distilled water were non-toxic to P. subcapitata, but were toxic to L. sativa. The acidic extracts were more toxic to P. subcapitata than to L. sativa. The methanolic organic extracts were more toxic to the alga than those obtained with dichloromethane. None of these extracts resulted toxic to L. sativa. Mutagenic effects were only detected in the organic dichloromethane extracts in the presence of metabolic activation. All the inorganic and organic extracts were genotoxic to A. cepa. This study showed that the implementation of different extraction methods together with a battery of bioassays could be suitable tools for detecting toxicity and genotoxicity in sediment samples.

Hospital effluent constitutes a source of vancomycin-resistant enterococci

We would like to acknowledge Cesar Criado Sanchez, Laboratory Technician of the Department of Preventive Medicine and Public Health, Faculty of Pharmacy, University of Granada, Spain, for his invaluable help in making this study possible. We also thank Jean Louise Sanders for translating and editing the manuscript.