Metabolism-based category formation for the prioritisation of genotoxicity hazard assessment for plant protection product residues (Part 4): α-Chloroacetamides.

In dietary risk assessment of plant protection products, residues of active ingredients and their metabolites need to be evaluated for their genotoxic potential. The European Food Safety Authority recommend a tiered approach focussing assessment and testing on classes of similar chemicals. To characterise similarity, in terms of metabolism, a metabolic similarity profiling scheme has been developed from an analysis of 69 α-chloroacetamide herbicides for which either Ames, chromosomal aberration or micronucleus test results are publicly available. A set of structural space alerts were defined, each linked to a key metabolic transformation present in the α-chloroacetamide metabolic space. The structural space alerts were combined with covalent chemistry profiling to develop categories suitable for chemical prioritisation via read-across. The method is a robust and reproducible approach to such read-across predictions, with the potential to reduce unnecessary testing. The key challenge in the approach was identified as being the need for metabolism data individual groups of plant protection products as the basis for the development of the structural space alerts.

Mutagenicity assessment of two potential impurities in preparations of 5-amino-2,4,6 triiodoisophthalic acid, a key intermediate in the synthesis of the iodinated contrast agent iopamidol.

5-Aminoisophthalic acid and 5-nitroisophthalic acid (5-NIPA) are potential impurities in preparations of 5-amino-2,4,6-triiodoisophthalic acid, which is a key intermediate in the synthesis of the iodinated contrast agent iopamidol. We have studied their mutagenicity in silico (quantitative structure-activity relationships, QSAR) and by the bacterial reverse mutation assay (Ames test). First, the compounds were screened with the tools Derek Nexus™ and Leadscope®. Both compounds were flagged as potentially mutagenic (class 3 under ICH M7). However, contrary to the in silico prediction, neither chemical was mutagenic in the Ames test (plate incorporation method) with or without S9 metabolic activation.

Mutagenic impurities in pharmaceuticals: A critical assessment of the cohort of concern with a focus on N-nitrosamines.

The TTC (Threshold of Toxicological Concern; set at 1.5 µg/day for pharmaceuticals) defines an acceptable patient intake for any unstudied chemical posing a negligible risk of carcinogenicity or other toxic effects. A group of high potency mutagenic carcinogens, defined solely by the presence of particular structural alerts, are referred to as the "cohort of concern" (CoC); aflatoxin-like-, N-nitroso-, and alkyl-azoxy compounds are considered to pose a significant carcinogenic risk at intakes below the TTC. Kroes et al. (2004) derived values for the TTC and CoC in the context of food components, employing a non-transparent dataset never placed in the public domain. Using a reconstructed all-carcinogen dataset from relevant publications, it is now clear that there are exceptions for all three CoC structural classes. N-Nitrosamines represent 62% of the N-nitroso class in the reconstructed dataset. Employing a contemporary dataset, 20% are negative in rodent carcinogenicity bioassays with less than 50% of all N-nitrosamines estimated to fall into the highest risk category. It is recommended that CoC nitrosamines are identified by compound-specific data rather than structural alerts. Thus, it should be possible to distinguish CoC from non-CoC N-nitrosamines in the context of mutagenic impurities described in ICH M7 (R1).

In vitro mutagenicity assessment of fried meat-based food from mass catering companies.

The current article aimed to evaluate the in vitro mutagenicity of ten fried meat-based food extracts obtained from different catering companies from Navarra (Spain). A miniaturized 6-well version of the Ames test in Salmonella typhimurium TA98, and the in vitro micronucleus test (OECD TG 487) in TK6 cells were performed. None of the ten extracts of fried meat-based food induced gene mutations in S. typhimurium TA98 with or without metabolic activation, but five induced chromosomal aberrations after 24 h treatment of TK6 without metabolic activation. More studies are needed to check the biological relevance of these in vitro studies.

Follow-up genotoxicity assessment of Ames-positive/equivocal chemicals using the improved thymidine kinase gene mutation assay in DNA repair-deficient human TK6 cells.

Genotoxicity testing plays an important role in the safety assessment of pharmaceuticals, pesticides and chemical substances. Among the guidelines for various genotoxicity tests, the in vitro genotoxicity test battery comprises the bacterial Ames test and mammalian cell assays. Several chemicals exhibit conflicting results for the bacterial Ames test and mammalian cell genotoxicity studies, which may stem from the differences in DNA repair capacity or metabolism, between different cell types or species. For better understanding the mechanistic implications regarding conflict outcomes between different assay systems, it is necessary to develop in vitro genotoxicity testing approaches with higher specificity towards DNA-damaging reagents. We have recently established an improved thymidine kinase (TK) gene mutation assay (TK assay) i.e. deficient in DNA excision repair system using human lymphoblastoid TK6 cells lacking XRCC1 and XPA (XRCC1-/-/XPA-/-), the core factors of base excision repair (BER) and nucleotide excision repair (NER), respectively. This DNA repair-deficient TK6 cell line is expected to specifically evaluate the genotoxic potential of chemical substances based on the DNA damage. We focussed on four reagents, N-(1-naphthyl)ethylenediamine dihydrochloride (NEDA), p-phenylenediamine (PPD), auramine and malachite green (MG) as the Ames test-positive chemicals. In our assay, assessment using XRCC1-/-/XPA-/- cells revealed no statistically significant increase in the mutant frequencies after treatment with NEDA, PPD and MG, suggesting the chemicals to be non-genotoxic in humans. The observations were consistent with that of the follow-up in vivo studies. In contrast, the mutant frequency was markedly increased in XRCC1-/-/XPA-/- cells after treatment with auramine. The results suggest that auramine is the genotoxic reagent that preferentially induces DNA damages resolved by BER and/or NER in mammals. Taken together, BER/NER-deficient cell-based genotoxicity testing will contribute to elucidate the mechanism of genotoxicity and therefore play a pivotal role in the accurate safety assessment of chemical substances.

Rapid characterization and pharmacokinetic study of aristolochic acid analogues using ion mobility mass spectrometry.

Aristolochic acid analogues (AAAs), naturally existing in herbal Aristolochia and Asarum genera, were once widely used in traditional pharmacopeias because of their anti-inflammatory properties, but lately they were identified as potential nephrotoxins and mutagens. A method for rapid characterization of AAAs in serum was developed using ion mobility spectrometry coupled with mass spectrometry (IMS-MS). Five AAAs, containing four aristolochic acids and one aristolactam, were separated and identified within milliseconds. AAAs were separated in gas phase based on the difference of their ion mobility (K0), and then identified based on their K0 values, m/z, and product ions from MS/MS. Quantitative analysis of AAAs was performed using an internal standard with a satisfactory sensitivity. Limits of detection (signal-to-noise = 3) and quantification (signal-to-noise = 10) were 1-5 ng/mL and 3-8 ng/mL, respectively. The method was validated and successfully applied to the pharmacokinetics study of AAAs in rats, offering a promising way for fast screening and evaluation of AAAs in biological samples.

Genotoxic and Cytotoxic Activities of Lantadene A-Loaded Gold Nanoparticles (LA-AuNPS) in MCF-7 Cell Line: An in vitro Assessment.

Gold nanoparticles (AuNPs) have been widely used in many applications. Their usage as drug delivery vehicles has also gained considerable attention due to their chemical and optical properties as well as their good biocompatibility. The present study was conducted to evaluate the efficiency of AuNPs in enhancing the cytotoxic and apoptotic induction activity of lantadene A (LA), separated from Lantana camara leaves, on the breast tumor cell line MCF-7 in vitro. By utilizing plant-mediated synthesis method of nanostructures, LA-loaded AuNPs (LA-AuNPs) were prepared and their formation was confirmed by means of ultraviolet-visible spectroscope, atomic force microscope, scanning electron microscope, and zeta potential. The cytotoxic effect of LA-AuNPs was analyzed using a methylthiazol tetrazolium assay and compared to free AuNPs and LA. The results indicated a significant increase in the reduction of MCF-7 cells viability after incubation with LA-AuNPs. As determined by terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) assay, LA-AuNPs induced a greater ratio of DNA-fragmented cells compared to LA-treated and untreated cells. Also, by operating real-time polymerase chain reaction, LA-AuNPs-treated cells displayed an increased upregulation of p53 expression and downregulation of BCL-2 expression in addition to a significant reduction in the level of BCL-2-BAX ratio. No significant effect was shown on the expression of BAX. Collectively, our results indicate that LA-AuNPs showed promising cytotoxicity to MCF-7 cells as a novel nanoscale preparation, likely via induction of apoptotic genes and stimulation of DNA fragmentation.

Synthesis, Characterization, Antimicrobial Activity, and Genotoxicity Assessment of Two Heterocyclic Compounds Containing 1,2,3-Selena- or 1,2,3-Thiadiazole Rings.

New 1,2,3-thiadiazole and 1,2,3-selenadiazole derivatives, (4-[4-((4-bromobenzyl)oxy)-phenyl]-1,2,3-thiadiazole (5a), 4-[4-((4-chlorobenzyl)oxy)-phenyl]-1,2,3-thiadiazole (5b)), (4-[4-((4-bromobenzyl)oxy)-phenyl]-1,2,3-selenadiazole (6a), and 4-[4-((4-chlorobenzyl)oxy)-phenyl]-1,2,3-selenadiazole (6b)), were prepared and screened in vitro for their antimicrobial activity against various pathogenic microbes. In addition, two compounds (5a and 6a) were examined for their in vivo genotoxicity using rats and an 8-hydroxy-2'-deoxyguanosine (8-OHdG) assay. Compounds 5a and 5b were found to be highly active against Gram-positive and Gram-negative bacteria. In addition, a significant inhibition of urinary 8-OHdG level (50.2%) was observed upon treatment of animals with 500 mg/kg body weight (b.w.) of compound 6a (p < 0.0001). However, compound 5a increased urinary 8-OHdG levels. The lethal dose (LD50) values for compounds 5a and 6a were determined by an up-and-down procedure (OECD 425; OECD 1998), which showed that these compounds are safe, since the LD50 was >5000 mg/kg b.w. Thus, the tested compounds might have the potential for use as antibiotics, since they have low genotoxicity and strong antimicrobial activity.

Integrated in silico and in vitro genotoxicity assessment of thirteen data-poor substances.

The Canadian Domestic Substances List (DSL) contains chemicals that have not been tested for genotoxicity as their use pre-dates regulatory requirements. In the present study, (quantitative) structure-activity relationships ((Q)SAR) model predictions and in vitro tests were conducted for genotoxicity assessment of 13 data-poor chemicals from the DSL (i.e. CAS numbers 19286-75-0, 13676-91-0, 2478-20-8, 6408-20-8, 74499-36-8, 26694-69-9, 29036-02-0, 120-24-1, 84696-48-9, 4051-63-2, 5718-26-3, 632-51-9, and 600-14-6). First, chemicals were screened by (Q)SAR models in Leadscope® and OASIS TIMES; two chemicals were excluded from (Q)SAR as they are complex mixtures. Six were flagged by (Q)SAR as potentially mutagenic and were subsequently confirmed as mutagens using the Ames assay. Of nine chemicals with clastogenic (Q)SAR flags, eight induced micronuclei in TK6 cells. Benchmark dose analysis was used to evaluate the potency of the chemicals. Four chemicals were bacterial mutagens with similar potencies. Three chemicals were more potent in micronuclei induction than the prototype alkylating agent methyl methanesulfonate and three were equipotent to the mutagenic carcinogen benzo[a]pyrene in the presence of rat liver S9. Overall, 11 of the 13 DSL chemicals demonstrated at least one type of genotoxicity in vitro. This study demonstrates the application of genotoxic potency analysis for prioritizing further investigations.

Assessment of the autoxidation mechanism of p-toluenediamine by air and hydrogen peroxide and determination of mutagenic environmental contaminant in beauty salon effluent.

The present work investigated the autoxidation reaction of p-toluenediamine (PTD) - a precursor - widely used in permanent hair dyeing formulation, under experimental conditions close to the hair dyeing process (oxygen and/or peroxide in ammoniacal medium), by chromatographic and spectroscopic techniques. In additional, evaluated the mutagenicity of the PTD oxidation products and the presence of PTD and this products in wastewater from beauty salon, as well as in surface water and drinking water using HPLC coupled to a diode array detector and linear scan voltammetry. Through this study, it was possible the identification of semi-quinonediimine, quinonediimine, dimers (derived from toluenediamine), and trimer radical identified as Bandrowski's Base derivative (BBD) formed during autoxidation of PTD. Salmonella Typhimurium YG1041 assay with and without metabolic activation induced rat-liver (S9) indicated mutagenic activity for BBD. Levels of PTD were determined by the standard addition method in samples collected from the wastewater of a beauty salon, as well as from the water before and after treatment in a drinking water treatment plant (DWTP) reached concentrations of 2.08 ±â€¯0.21, 2.36 ±â€¯0.10 × 10-3, and 1.77 ±â€¯0.13 × 10-3 mg L-1, respectively. In addition, linear sweep voltammetry was used to monitor the BBD found at the concentration of 1.59 ±â€¯0.35 mg L-1 in wastewater collected from the beauty salon.

Use of in vitro bioassays to facilitate read-across assessment of nitrogen substituted heterocycle analogues of polycyclic aromatic hydrocarbons.

Nitrogen-containing polycyclic aromatic hydrocarbons (PANHs or azaarenes) are compounds structurally similar to PAHs (carbon substituted by a nitrogen) reported to occur at low levels in food. Although limited, literature may suggest possible higher toxicity than for PAHs. Using a battery of in vitro assays, the toxicological properties of uncharacterized PANHs of increasing ring number were compared to those of characterized structural PAH analogues. The parameters measured covered key events relevant to the AOP developed for Benzo(a)pyrene: AhR activation, mutagenicity and DNA-damage with and without metabolic activation and endocrine receptors activation/inhibition. There was a strong correlation between the chemical structure and the biological activities of the compounds. AhR activation was the most sensitive parameter with a direct correlation between potency and ring number. The most potent genotoxic chemicals were found amongst the ones with the highest number of ring, and under metabolic activation. Such an approach allowed designing sub-groups based on biological properties in addition to structural similarities. Within a sub-group, toxicological data of tested chemicals may be used to characterize hazard of biologically similar but toxicologically uncharacterized substances. This indicates that in addition to structural properties, in vitro biological data may be useful to conduct read-across.

Assessment of silver nanoparticles decorated starch and commercial zinc nanoparticles with respect to their genotoxicity on onion.

High throughput production of silver nanoparticles (AgNPs) having controlled size appropriate for industrial purposes were achieved via using facile and ecofriendly chemical reduction method. Native rice starch was used as reductant for silver ions (Ag+) to silver atoms (Ag0), as well as stabilizing for the obtainable AgNPs. Two different concentrations; 2000 ppm and 4000 ppm were successfully prepared and coded as AgNPs-2000 and AgNPs-4000 respectively. The attained AgNPs were characterized via ultra-visible (UV-vis) spectra, Transmission Electron Microscope (TEM), Energy dispersive X-ray (EDX), Particle size analyzer, polydispersity index (PDI) and zeta potential (ζ-potential). The average particle size of AgNPs (2000 ppm) was 8 nm with PDI = 0.01 which affirm the monodispersity and homogeneity of the produced AgNPs. Meanwhile, the size majority for the as prepared AgNPs (4000 ppm) was 24 nm with PDI = 0.021. Based on the aforementioned data, AgNPs prepared with a high concentration (4000 ppm) compared with the commercialized ZnNPs were used for the genotoxicity study on onion. Root-tips was used for cytogenetic studies using onion (Allium cepa L.) which are excellent materials for cytological and genotoxicity studies. Genotoxicity results explored that, by using AgNPs ≥40 ppm, the abnormalities disturbed chromosomes were observed and detected, that reflects the genotoxicity effect of these nanoparticles at this dose. In addition, the commercial available ZnNPs with the recommended dose (2 g/L) displayed also severe genotoxicity on A. cepa L. root meristem cells.

In vitro genotoxicity assessment of an oxidized dextrin-based hydrogel for biomedical applications.

Hydrogels are three-dimensional, crosslinked networks of hydrophilic polymers swollen with a large amount of water or biological fluids, without dissolving. Dextrin, a low-molecular-weight carbohydrate composed by glucose residues, has been used to develop an injectable hydrogel for biomedical applications. Dextrin was first oxidized to introduce aldehyde groups, which then reticulate with adipic acid dihydrazide, forming the dextrin-based hydrogel (HG). The HG and its components were tested for cyto- and genotoxicity according to the International Standard ISO 10993-3 on the biological evaluation of medical devices. To assess genotoxicity, a battery of in vitro genotoxicity tests employing both eukaryotic and prokaryotic models was performed: comet assay, cytokinesis-block micronucleus assay and Ames test. Our data revealed that the HG (IC50  = 2.8 mg/mL) and oxidized dextrin by itself (IC50  = 1.2 mg/mL) caused a concentration-dependent decrease in cellular viability of human lymphoblastoid TK6 cells after 24 hours of exposure to the test agents. However, these concentrations are unlikely to be reached in vivo. In addition, no significant increase in the DNA and chromosomal damage of TK6 cells exposed to non-cytotoxic concentrations of the HG and its isolated components was detected. Furthermore, neither the HG nor its metabolites exerted a mutagenic effect in different of Salmonella typhimurium strains and in an Escherichia coli mix. Our data demonstrated the genocompatibility of the HG (up to 3.5 mg/mL) for biomedical applications. To our best acknowledge, this is the first report with a detailed genotoxicity assessment of an aldehyde-modified polysaccharide/adipic acid dihydrazide hydrogel.

A decision tree-based integrated testing strategy for tailor-made carcinogenicity evaluation of test substances using genotoxicity test results and chemical spaces.

Genotoxicity evaluation has been widely used to estimate the carcinogenicity of test substances during safety evaluation. However, the latest strategies using genotoxicity tests give more weight to sensitivity; therefore, their accuracy has been very low. For precise carcinogenicity evaluation, we attempted to establish an integrated testing strategy for the tailor-made carcinogenicity evaluation of test materials, considering the relationships among genotoxicity test results (Ames, in vitro mammalian genotoxicity and in vivo micronucleus), carcinogenicity test results and chemical properties (molecular weight, logKow and 179 organic functional groups). By analyzing the toxicological information and chemical properties of 230 chemicals, including 184 carcinogens in the Carcinogenicity Genotoxicity eXperience database, a decision tree for carcinogenicity evaluation was optimised statistically. A decision forest model was generated using a machine-learning method-random forest-which comprises thousands of decision trees. As a result, balanced accuracies in cross-validation of the optimised decision tree and decision forest model, considering chemical space (71.5% and 75.5%, respectively), were higher than balanced accuracy of an example regulatory decision tree (54.1%). Moreover, the statistical optimisation of tree-based models revealed significant organic functional groups that would cause false prediction in standard genotoxicity tests and non-genotoxic carcinogenicity (e.g., organic amide and thioamide, saturated heterocyclic fragment and aryl halide). In vitro genotoxicity tests were the most important parameters in all models, even when in silico parameters were integrated. Although external validation is required, the findings of the integrated testing strategies established herein will contribute to precise carcinogenicity evaluation and to determine new mechanistic hypotheses of carcinogenicity.

3-NOP: Mutagenicity and genotoxicity assessment.

3-NOP (3-nitroxy-propanol) is a new development compound which reduces methane emission from ruminating animals. For registration purposes with emphasis on EU and North America data requirements, mutagenic and genotoxic potential was assessed following OECD protocols and respective guidance documents. 3-NOP mutagenicity and genotoxicity testing raised no flags with regard to these endpoints. In silico assessment of 3-NOP and its major plasma metabolite NOPA (3-nitroxy-propionic acid) were predicted negative with regard to the bacterial reverse mutation (Ames) test. Ames test, mouse lymphoma assay, in vitro micronucleus test, and the oral in vivo micronucleus test using rat bone marrow were all negative. Exposure of the rat bone marrow was verified by the presence of 3-NOP and its metabolites NOPA and HPA (3-hydroxy-propionic acid) a naturally occurring substance in mammals) in plasma following oral dosing. It is therefore concluded that 3-NOP and its metabolites pose no mutagenic and genotoxic potential.

Use of the index of ideality of correlation to improve predictive potential for biochemical endpoints.

The CORAL software is a tool to build up quantitative structure-property/activity relationships (QSPRs/QSARs). The project of updated version of the CORAL software is discussed in terms of practical applications for building up various models. The updating is the possibility to improve the predictive potential of models using the so-called Index of Ideality of Correlation (IIC) as a criterion of the predictive potential for QSPR/QSAR models. Efficacy of the IIC is examined with three examples of building up QSARs: (i) models for anticancer activity; (ii) models for mutagenicity; and (iii) models for toxicity of psychotropic drugs. The validation of these models has been carried out with several splits into the training, invisible training, calibration, and validation sets. The ability of IIC to be an indicator of predictive potential of QSAR models is confirmed. The updated version of the CORAL software (CORALSEA-2017, http://www.insilico.eu/coral ) is available on the Internet.

Managing emerging mutagenicity risks: Late stage mutagenic impurity control within the atovaquone second generation synthesis.

The mutagenic-impurity control strategy for a second generation manufacturing route to the non-mutagenic antipneumocystic agent atovaquone (2-((1R,4R)-4-(4-chlorophenyl)cyclohexyl)-3-hydroxynaphthalene-1,4-dione) 1 is described. Preliminary assessment highlighted multiple materials of concern which were largely discharged either through returning a negative bacterial mutagenicity assay or through confidence that the impurity would be purged during the downstream processing from when it was first introduced. Additional genotoxicity testing highlighted two materials of concern where initial assessment suggested that testing for these impurities at trace levels within the drug substance would be required. Following a thorough review of process purging detail, spiking and purging experimentation, and an understanding of the process parameters to which they were exposed an ICH M7 Option 4 approach could be justified for their control. The development of two 1H NMR spectroscopy methods for measurement of these impurities is also described as well as a proposed summary table for describing the underlying rationale for ICH M7 control rationales to regulators. This manuscript demonstrates that process purging of potential mutagenic impurities can be realised even when they are introduced in the later stages of a process and highlights the importance of scientific understanding rather than relying on a stage-counting approach.

Mathematical structural descriptors and mutagenicity assessment: a study with congeneric and diverse datasets$.

Quantitative bioactivity and toxicity assessment of chemical compounds plays a central role in drug discovery as it saves a substantial amount of resources. To this end, high-performance computing has enabled researchers and practitioners to leverage hundreds, or even thousands, of computed molecular descriptors for the activity prediction of candidate compounds. In this paper, we evaluate the utility of two large groups of chemical descriptors by such predictive modelling, as well as chemical structure discovery, through empirical analysis. We use a suite of commercially available and in-house software to calculate molecular descriptors for two sets of chemical mutagens - a homogeneous set of 95 amines, and a diverse set of 508 chemicals. Using calculated descriptors, we model the mutagenic activity of these compounds using a number of methods from the statistics and machine-learning literature, and use robust principal component analysis to investigate the low-dimensional subspaces that characterize these chemicals. Our results suggest that combining different sets of descriptors is likely to result in a better predictive model - but that depends on the compounds being modelled and the modelling technique being used.

Initial hazard assessment of 4-benzylphenol, a structural analog of bisphenol F: Genotoxicity tests in vitro and a 28-day repeated-dose toxicity study in rats.

4-Benzylphenol (CAS No. 101-53-1), a structural analog of bisphenol F, has estrogenic activity in vitro and in vivo, as is the case with bisphenol F. 4-Benzylphenol is used in plastics and during organic synthesis. Since its safety is largely unknown, we conducted toxicity tests as part of screening risk assessment in an existing chemical safety survey program. Based on results of the Ames test and the chromosomal aberration test using Chinese hamster lung cells (OECD TG 471 and 473), 4-benzylphenol was determined to be non-genotoxic in vitro. In a 28-day repeated-dose toxicity study, Crl:CD (SD) rats were administrated 4-benzylphenol by gavage at 0, 30, 150, or 750 mg/kg/day (OECD TG 407). Consequently, body weight was lower in males at 750 mg/kg/day. In the liver, relative organ weights were increased in both sexes at 750 mg/kg/day, and centrilobular hepatocellular hypertrophy was observed in males at 150 and 750 mg/kg/day. In the forestomach, hyperkeratosis and hyperplasia of squamous cells were observed in males at 150 and 750 mg/kg/day, and in females at 750 mg/kg/day. Based on these results, we identified the NOAEL for 4-benzylphenol as 30 mg/kg/day, with a hazard assessment value (D-value) of 0.05 mg/kg/day corresponding to hazard class 3.

Dioxin-like compounds bioavailability and genotoxicity assessment in the Gulf of Follonica, Tuscany (Northern Tyrrhenian Sea).

The Gulf of Follonica (Italy) is impacted by the chemical pollution from ancient mining activity and present industrial processes. This study was aimed to determine the bioavailability of dioxin-like compounds (DLCs) in coastal marine environment and to assess the genotoxic potential of waste waters entering the sea from an industrial canal. Moderately high levels of DCLs compounds (∑ PCDDs + PCDFs 2.18­29.00 pg/g dry wt) were detected in Mytilus galloprovincialis transplanted near the waste waters canal and their corresponding Toxic Equivalents (TEQs) calculated. In situ exposed mussels did not show any genotoxic effect (by Comet and Micronucleus assay). Otherwise, laboratory exposure to canal waters exhibited a reduced genomic template stability (by RAPD-PCR assay) but not DNA or chromosomal damage. Our data reveal the need to focus on the levels and distribution of DLCs in edible species from the study area considering their potential transfer to humans through the consumption of sea food.