Search for the optimal genotoxicity assay for routine testing of chemicals: Sensitivity and specificity of conventional and new test systems

Many conventional in vitro tests that are currently widely used for routine screening of chemicals have a sensitivity/specificity in the range between 60 % and 80 % for the detection of carcinogens. Most procedures were developed 30-40 years ago. In the last decades several assays became available which are based on the use of metabolically competent cell lines, improvement of the cultivation conditions and development of new endpoints. Validation studies indicate that some of these models may be more reliable for the detection of genotoxicants (i.e. many of them have sensitivity and specificity values between 80 % and 95 %). Therefore, they could replace conventional tests in the future. The bone marrow micronucleus (MN) assay with rodents is at present the most widely used in vivo test. The majority of studies indicate that it detects only 5-6 out of 10 carcinogens while experiments with transgenic rodents and comet assays seem to have a higher predictive value and detect genotoxic carcinogens that are negative in MN experiments. Alternatives to rodent experiments could be MN experiments with hen eggs or their replacement by combinations of new in vitro tests. Examples for promising candidates are ToxTracker, TGx-DDI, multiplex flow cytometry, γH2AX experiments, measurement of p53 activation and MN experiments with metabolically competent human derived liver cells. However, the realization of multicentric collaborative validation studies is mandatory to identify the most reliable tests.

Comparison of the in vivo genotoxicity of electronic and conventional cigarettes aerosols after subacute, subchronic and chronic exposures

Tobacco smoking is classified as a human carcinogen. A wide variety of new products, in particular electronic cigarettes (e-cigs), have recently appeared on the market as an alternative to smoking. Although the in vitro toxicity of e-cigs is relatively well known, there is currently a lack of data on their long-term health effects. In this context, the aim of our study was to compare, on a mouse model and using a nose-only exposure system, the in vivo genotoxic and mutagenic potential of e-cig aerosols tested at two power settings (18 W and 30 W) and conventional cigarette (3R4F) smoke. The standard comet assay, micronucleus test and Pig-a gene mutation assay were performed after subacute (4 days), subchronic (3 months) and chronic (6 months) exposure. The generation of oxidative stress was also assessed by measuring the 8-hydroxy-2'-deoxyguanosine and by using the hOGG1-modified comet assay. Our results show that only the high-power e-cig and the 3R4F cigarette induced oxidative DNA damage in the lung and the liver of exposed mice. In return, no significant increase in chromosomal aberrations or gene mutations were noted whatever the type of product. This study demonstrates that e-cigs, at high-power setting, should be considered, contrary to popular belief, as hazardous products in terms of genotoxicity in mouse model.

In Silico Methods for Chromosome Damage

Due to the link with serious adverse health effects, genotoxicity is an important toxicological endpoint in each regulatory setting with respect to human health, including for pharmaceuticals. To this extent, a compound potential to induce gene mutations as well as chromosome damage needs to be addressed. For chromosome damage, i.e., the induction of structural or numerical chromosome aberrations, several in vitro and in vivo test methods are available. In order to rapidly collect toxicological data without the need for test material, several in silico tools for chromosome damage have been developed over the last years. In this chapter, a battery of freely available in silico chromosome damage prediction tools for chromosome damage is applied on a dataset of pharmaceuticals. Examples of the different outcomes obtained with the in silico battery are provided and briefly discussed. Furthermore, results for coumarin are presented in more detail as a case study. Overall, it can be concluded that although they are in general less developed than those for mutagenicity, in silico tools for chromosome damage can provide valuable information, especially when combined in a battery.

Safety and efficacy of a feed additive consisting of an aqueous extract of Citrus limon (L.) Osbeck (lemon extract) for use in all animal species (Nor-Feed SAS)

Following a request from the European Commission, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety and efficacy of an aqueous extract of Citrus limon (L.) Osbeck (lemon extract) when used as a sensory additive in feed for all animal species. The FEEDAP Panel concluded that the additive under assessment is safe for all animal species up to the maximum proposed use levels of 1,000 mg/kg complete feed and 250 mg/kg water for drinking. No concerns for consumers were identified following the use of lemon extract up to the highest safe level in feed. The additive should be considered a skin and eye irritant, and a potential corrosive. The use of the extract in animal feed under the proposed conditions was not expected to pose a risk for the environment. Lemon extract was recognised to flavour food. Since its function in feed would be essentially the same as that in food, no further demonstration of efficacy was considered necessary.

Prediction of Micronucleus Assay Outcome Using In Vivo Activity Data and Molecular Structure Features

In vivo micronucleus assay is the widely used genotoxic test to determine the extent of chromosomal aberrations caused by the chemicals in human beings, which plays a significant role in the drug discovery paradigm. To reduce the uncertainties of the in vivo experiments and the expenses, we intended to develop novel machine learning-based tools to predict the toxicity of the compounds with high precision. A total of 372 compounds with known toxicity information were retrieved from the PubChem Bioassay database and literature. The fingerprints and descriptors of the compounds were generated using PaDEL and ChemSAR, respectively, for the analysis. The performance of the models was assessed using the three tires of evaluation strategies such as fivefold, tenfold, and validation by external dataset. Further, structural alerts causing genotoxicity of the compounds were identified using SARpy method. Of note, fingerprint-based random forest model built in our analysis is able to demonstrate the highest accuracy of about 0.97 during tenfold cross-validation. In essence, our study highlights that structural alerts such as chlorocyclohexane and trimethylamine are likely to be the leading cause of toxicity in humans. Indeed, we believe that random forest model generated in this study is appropriate for reduction of test animals and should be considered in the future for the good practice of animal welfare.

Towards prevention of ischemia-reperfusion kidney injury: Pre-clinical evaluation of 6-chromanol derivatives and the lead compound SUL-138✰

Acute kidney injury (AKI) is a global healthcare burden attributable to high mortality and staggering costs of dialysis. The underlying causes of AKI include hypothermia and rewarming (H/R), ischemia/reperfusion (I/R), mitochondrial dysfunction and reactive oxygen species production. Inspired by the mechanisms conferring organ protection in hibernating hamster, 6-chromanol derived compounds were developed to address the need of effective prevention and treatment of AKI. Here we report on the pre-clinical screening of 6-chromanol leads that confer protection during I/R to select compounds with favorable profiles for clinical testing in AKI. A library of 6-chromanols (n = 63) was screened in silico for pharmacochemical properties and druggability. Selected compounds (n = 15) were screened for the potency to protect HEK293 cells from H/R cell death and subjected to a panel of in vitro safety assays. Based on these parameters, SUL-138 was selected as the lead compound and was found to safeguard kidney function and decrease renal injury after I/R in rats. The compound was without cardiovascular or respiratory effects in vivo. SUL-138 pharmacokinetics of control animals (mouse, rat) and those undergoing I/R (rat) was identical, showing a two-phase elimination profile with terminal half-life of about 8 h. Collectively, our phenotype-based screening approach led to the identification of 3 candidates for pre-clinical studies (5%, 3/64). SUL-138 emerged from this small-scale library of 6-chromanols as a novel prophylactic for AKI. The presented efficacy and safety data provide a basis for future development and clinical testing. SECTION ASSIGNMENTS: : Drug discovery and translational medicine, renal, metabolism SIGNIFICANCE STATEMENT: : Based on in silico druggability parameters, a 63 compound 6-chromanol library was narrowed down to 15 compounds. These compounds were subjected to phenotypical screening of cell survival following hypothermia damage and hit compounds were identified. After subsequent assessment of in vivo efficacy, toxicity, pharmacokinetics, and cardiovascular and respiratory safety, SUL-138 emerged as a lead compound that prevented kidney injury after ischemia/reperfusion and demonstrated a favorable pharmacokinetic profile unaffected by renal ischemia.

Hazard assessment using an in-silico toxicity assessment of the transformation products of boscalid, pyraclostrobin, fenbuconazole and glyphosate generated by exposure to an advanced oxidative process

Agricultural pesticide use is ongoing and consumer concern regarding the safety of pesticide residues on produce has generated interest in techniques that can safely reduce residues post-harvest. Recently an advanced oxidative process has shown promise in substantial residue reduction on the surface of produce. Given the potential for oxidative transformation of pesticides to generate transformation products with greater toxicity than the parent residue, take for example the oxon products of the organophosphorus insecticides, it is important to consider what transformation products are generated by pesticide exposure to an oxidative process and their potential toxicity. In this study, previously published transformation products of boscalid, pyraclostrobin, fenbuconazole and glyphosate were identified after exposure to 3% hydrogen peroxide, UV-C irradiation or their combination in an advanced oxidative process on glass, their oral toxicity, carcinogenicity and developmental toxicity were identified in-silico and an initial tier hazard assessment was conducted. Of the 87 total structures that were searched for, 53 were detected by UPLC-QTOF-MS and identified by mass spectra: 15, 13, 22 and 3 structures for boscalid, pyraclostrobin, fenbuconazole and glyphosate respectively, including the parent residues. Oral toxicity of the transformation products of pyraclostrobin and glyphosate was similar to or lower than the parent residue. Several transformation products of boscalid and fenbuconazole were estimated to be significantly more orally toxic than their parent residues. While the majority of the transformation products of boscalid, pyraclostrobin and fenbuconazole were predicted to be carcinogenic there were 11 that were consistently identified to have carcinogenic potential by several assessments. 29 of the 53 molecules were predicted to be probable developmental toxicants. An initial tier hazard assessment was conducted for Cramer rules classification and mutagenicity using the threshold of toxicological concern approach and predicted rat oral LD50. Two exposure scenarios were considered, one highly protective considering each transformation product to be at the highest maximum residue limit (MRL) for the pesticide and whole produce consumption at the highest consumption rate from the USEPA Exposures Handbook, the other considering only apple consumption with the relevant MRL. As indicated by the hazard assessment, several transformation products of boscalid, pyraclostrobin and fenbuconazole should be strongly considered for further testing, either by quantifying their production or in-vivo and in-vitro toxicity tests due to their predicted toxicity and associated hazard.

New in silico models to predict in vitro micronucleus induction as marker of genotoxicity

The evaluation of genotoxicity is a fundamental part of the safety assessment of chemicals due to the relevance of the potential health effects of genotoxicants. Among the testing methods available, the in vitro micronucleus assay with mammalian cells is one of the most used and required by regulations targeting several industrial sectors such as the cosmetic industry and food-related sectors. As an alternative to the testing methods, in recent years, lots in silico methods were developed to predict the genotoxicity of chemicals, including models for the Ames mutagenicity test, the in vitro chromosomal aberrations and the in vivo micronucleus assay. We developed several in silico models for the prediction of genotoxicity as reflected by the in vitro micronucleus assay. The resulting models include both statistical and knowledge-based models. The most promising model is the one based on fragments extracted with the SARpy platform. More than 100 structural alerts were extracted, including also fragments associated with the non-genotoxic activity. The model is characterized by high accuracy and the lowest false negative rate, making this tool suitable for chemical screening according to the regulators' needs. The SARpy model will be implemented on the VEGA platform (https://www.vegahub.eu) and will be freely available.

Re-evaluation of l(+)-tartaric acid (E 334), sodium tartrates (E 335), potassium tartrates (E 336), potassium sodium tartrate (E 337) and calcium tartrate (E 354) as food additives

The EFSA Panel on Food Additives and Flavourings (FAF) provides a scientific opinion on tartaric acid-tartrates (E 334-337, 354) when used as food additives. The Scientific Committee for Food (SCF) in 1990 established an acceptable daily intake (ADI) of 30 mg/kg body weight (bw) per day, for l(+)-tartaric acid and its potassium and sodium salts. The metabolism of l(+)-tartaric acid and its potassium sodium salt was shown to be species dependent, with a greater absorption in rats than in humans. No toxic effects, including nephrotoxicity, were observed in toxicological studies in which the l(+)-form was tested. There was no indication for a genotoxic potential of tartaric acid and its sodium and potassium salts. In a chronic study in rats, no indication for carcinogenicity of monosodium l(+)-tartrate was reported at the highest dose tested (3,100 mg/kg bw per day). The available studies for maternal or developmental toxicity did not report any relevant effects; no studies for reproductive toxicity were available; however, no effects on reproductive organs were observed in the chronic toxicity study. The Panel concluded that the data on systemic availability were robust enough to derive a chemical-specific uncertainty factor instead of the usual default uncertainty factor of 100. A total uncertainty factor of 10 was derived by applying a total interspecies uncertainty factor of 1 instead of 10, based on data showing lower internal exposure in humans compared to rats. The Panel established a group ADI for l(+)-tartaric acid-tartrates (E 334-337 and E 354) of 240 mg/kg bw per day, expressed as tartaric acid, by applying the total uncertainty factor of 10 to the reference point of 3,100 mg sodium tartrate/kg bw per day, approximately to 2,440 mg tartaric acid/kg bw per day. The exposure estimates for the different population groups for the refined non-brand-loyal exposure scenario did not exceed the group ADI of 240 mg/kg bw per day, expressed as tartaric acid. Some recommendations were made by the Panel.

Re-evaluation of acetic acid, lactic acid, citric acid, tartaric acid, mono- and diacetyltartaric acid, mixed acetic and tartaric acid esters of mono- and diglycerides of fatty acids (E 472a-f) as food additives

The Panel on Food Additives and Flavourings (FAF) provided a scientific opinion re-evaluating the safety of acetic acid, lactic acid, citric acid, tartaric acid, mono- and diacetyltartaric acids, mixed acetic and tartaric acid esters of mono- and diglycerides of fatty acids (E 472a-f) as food additives. All substances had been previously evaluated by the Scientific Committee for Food (SCF) and by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Hydrolysis of E472a,b,c,e was demonstrated in various experimental systems, although the available data on absorption, distribution, metabolism, excretion (ADME) were limited. The Panel assumed that E472a-f are extensively hydrolysed in the GI tract and/or (pre-)systemically after absorption into their individual hydrolysis products which are all normal dietary constituents and are metabolised or excreted intact. No adverse effects relevant for humans have been identified from the toxicological database available for E472a-f. The Panel considered that there is no need for a numerical acceptable daily intake (ADI) for E 472a,b,c. The Panel also considered that only l(+)-tartaric acid has to be used in the manufacturing process of E472d,e,f. The Panel established ADIs for E 472d,e,f based on the group ADI of 240 mg/kg body weight (bw) per day, expressed as tartaric acid, for l(+)-tartaric acid-tartrates (E334-337, 354) and considering the total amount of l(+)-tartaric acid in each food additive. Exposure estimates were calculated for all food additives individually, except for E 472e and f, using maximum level, refined exposure and food supplements consumers only scenarios. Considering the exposure estimates, there is no safety concern at their reported uses and use levels. In addition, exposure to tartaric acid released from the use of E 472d,e,f was calculated. The Panel also proposed a number of recommendations.

Development of improved QSAR models for predicting the outcome of the in vivo micronucleus genetic toxicity assay

All drugs entering clinical trials are expected to undergo a series of in vitro and in vivo genotoxicity tests as outlined in the International Council on Harmonization (ICH) S2 (R1) guidance. Among the standard battery of genotoxicity tests used for pharmaceuticals, the in vivo micronucleus assay, which measures the frequency of micronucleated cells mostly from blood or bone marrow, is recommended for detecting clastogens and aneugens. (Quantitative) structure-activity relationship [(Q)SAR] models may be used as early screening tools by pharmaceutical companies to assess genetic toxicity risk during drug candidate selection. Models can also provide decision support information during regulatory review as part of the weight-of-evidence when experimental data are insufficient. In the present study, two commercial (Q)SAR platforms were used to construct in vivo micronucleus models from a recently enhanced in-house database of non-proprietary study findings in mice. Cross-validated performance statistics for the new models showed sensitivity of up to 74% and negative predictivity of up to 86%. In addition, the models demonstrated cross-validated specificity of up to 77% and coverage of up to 94%. These new models will provide more reliable predictions and offer an investigational approach for drug safety assessment with regards to identifying potentially genotoxic compounds.

In silico prediction of chromosome damage: comparison of three (Q)SAR models

Two major endpoints for genotoxicity tests are gene mutation and chromosome damage (CD), which includes clastogenicity and aneugenicity detected by chromosomal aberration (CA) test or micronucleus (MN) test. Many in silico prediction systems for bacterial mutagenicity (i.e. Ames test results) have been developed and marketed. They show good performance for prediction of Ames mutagenicity. On the other hand, it seems that in silico prediction of CD does not progress as much as Ames prediction. Reasons for this include different mechanisms and detection methods, many false positives and conflicting test results. However, some (quantitative) structure-activity relationship ((Q)SAR) models (e.g. Derek Nexus [Derek], ADMEWorks [AWorks] and CASE Ultra [MCase]) can predict CA test results. Therefore, performances of the three (Q)SAR models were compared using the expanded Carcinogenicity Genotoxicity eXperience (CGX) dataset for understanding current situations and future development. The constructed dataset contained 440 chemicals (325 carcinogens and 115 non-carcinogens). Sensitivity, specificity, accuracy or applicability of each model were 56.0, 86.9, 68.6 or 89.1% in Derek, 67.7, 61.5, 65.2 or 99.3% in AWorks, and 91.0, 64.9, 80.5 or 97.7% in MCase, respectively. The performances (sensitivity and accuracy) of MCase were higher than those of Derek or AWorks. Analysis of predictivity of (Q)SAR models of certain chemical classes revealed no remarkable differences among the models. The tendency of positive prediction by (Q)SAR models was observed in alkylating agents, aromatic amines or amides, aromatic nitro compounds, epoxides, halides and N-nitro or N-nitroso compounds. In an additional investigation, high sensitivity but low specificity was noted in in vivo MN prediction by MCase. Refinement of test data to be used for in silico system (e.g. consideration of cytotoxicity or re-evaluation of conflicting test results) will be needed to improve performance of CD prediction.

Overview of available toxicity data for calystegines

Calystegines are polyhydroxylated nortropane alkaloids that have been found in various solanaceous foods, in particular in potatoes and aubergines. The biological activity and potential toxicity of calystegines are associated with their capacity to inhibit glycosidases and block carbohydrate metabolism inducing lysosomal storage toxicity. The present report summarises the retrieved information on the possible toxicity of calystegines. Only few in vivo short‐term toxicological studies in rodents on individual calystegines or mixtures of calystegines were retrieved. Overall, these studies are insufficient to conclude on the possible chronic toxicity effects of calystegines in humans, in particular considering the short duration of the studies and potential lower sensitivity of rats and mice to glycosidase inhibitors, compared to other species such as goats and guinea pigs. Several studies and case reports were retrieved on the toxic effects induced in livestock or experimental animals following consumption or administration of plants containing calystegines. However, the concurrent presence of other alkaloids, in particular swainsonine, did not allow using these studies to draw conclusions on the toxicity of calystegines. Since no experimental data on genotoxicity of calystegines were retrieved, in silico predicting models were applied to identify possible alert for genotoxicity of five calystegines recently detected in food. In most of the cases, the outcome of the computational predictions indicated no alerts for genotoxicity; however, the low reliability of the results prevents a firm conclusion on the genotoxic potential of the substances. Overall, the available data do not allow drawing conclusions on the possible toxic effects of calystegines in humans or in livestock, and more data in relevant experimental models would be necessary to characterise the toxic profile of this group of substances.

Re-evaluation of carrageenan (E 407) and processed Eucheuma seaweed (E 407a) as food additives

The present opinion deals with the re-evaluation of the safety of food-grade carrageenan (E 407) and processes Eucheuma seaweed (E 407a) used as food additives. Because of the structural similarities, the Panel concluded that processed Eucheuma seaweed can be included in the evaluation of food-grade carrageenan. Poligeenan (average molecular weight 10-20 kDa) has not been authorised as a food additive and is not used in any food applications. In its evaluation of carrageenan (E 407) and processed Eucheuma seaweed (E 407a), the Panel noted that the ADME database was sufficient to conclude that carrageenan was not absorbed intact; in a subchronic toxicity study performed with carrageenan almost complying with the EU specification for E 407 in rats, the no-observed-adverse-effect level (NOAEL) was 3,400-3,900 mg/kg body weight (bw) per day, the highest dose tested; no adverse effects have been detected in chronic toxicity studies with carrageenan in rats up to 7,500 mg/kg bw per day, the highest dose tested; there was no concern with respect to the carcinogenicity of carrageenan; carrageenan and processed Eucheuma seaweed did not raise a concern with respect to genotoxicity; the NOAEL of sodium and calcium carrageenan for prenatal developmental dietary toxicity studies were the highest dose tested; the safety of processed Eucheuma seaweed was sufficiently covered by the toxicological evaluation of carrageenan; data were adequate for a refined exposure assessment for 41 out of 79 food categories. However, the Panel noted uncertainties as regards the chemistry, the exposure assessment and biological and toxicological data. Overall, taking into account the lack of adequate data to address these uncertainties, the Panel concluded that the existing group acceptable daily intake (ADI) for carrageenan (E 407) and processed Eucheuma seaweed (E 407a) of 75 mg/kg bw per day should be considered temporary, while the database should be improved within 5 years after publication of this opinion.

In silico prediction of chemical genotoxicity using machine learning methods and structural alerts

Genotoxicity tests can detect compounds that have an adverse effect on the process of heredity. The in vivo micronucleus assay, a genotoxicity test method, has been widely used to evaluate the presence and extent of chromosomal damage in human beings. Due to the high cost and laboriousness of experimental tests, computational approaches for predicting genotoxicity based on chemical structures and properties are recognized as an alternative. In this study, a dataset containing 641 diverse chemicals was collected and the molecules were represented by both fingerprints and molecular descriptors. Then classification models were constructed by six machine learning methods, including the support vector machine (SVM), naïve Bayes (NB), k-nearest neighbor (kNN), C4.5 decision tree (DT), random forest (RF) and artificial neural network (ANN). The performance of the models was estimated by five-fold cross-validation and an external validation set. The top ten models showed excellent performance for the external validation with accuracies ranging from 0.846 to 0.938, among which models Pubchem_SVM and MACCS_RF showed a more reliable predictive ability. The applicability domain was also defined to distinguish favorable predictions from unfavorable ones. Finally, ten structural fragments which can be used to assess the genotoxicity potential of a chemical were identified by using information gain and structural fragment frequency analysis. Our models might be helpful for the initial screening of potential genotoxic compounds.

Re-evaluation of polyglycerol esters of fatty acids (E 475) as a food additive

The EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of polyglycerol esters of fatty acids (PEFA) (E 475) when used as a food additive. In 1978, the Scientific Committee on Food (SCF) endorsed an acceptable daily intake (ADI) of 25 mg/kg body weight (bw) per day previously established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA). Absorption of intact PEFA in the gastrointestinal tract was extremely low. PEFA was rapidly and almost fully hydrolysed to polyglycerols and fatty acids in the gastrointestinal tract. The safety of polyglycerols and specific fatty acids has recently been assessed and no adverse effects were identified in the available studies. No adverse effects of PEFA at any dose have been observed in short‐term, subchronic or chronic toxicity studies. A no observed adverse effect level (NOAEL) of 9,000 mg/kg bw per day was identified from subchronic studies and of 2,500 mg/kg bw per day from chronic studies, the highest doses tested. No genotoxic potential of PEFA was identified from the limited information available. The reproductive toxicity studies showed no adverse effects of PEFA but had major limitations. Clinical chemistry and urinalysis, from a clinical study with limited information, did not reveal any adverse effects in volunteers receiving up to 300 mg/kg bw per day for 3 weeks. The highest exposure to PEFA used as a food additive was 2.6 and 6.4 mg/kg bw per day in children at the mean and the 95th percentile, respectively, for the non‐brand loyal scenario. Considering all the above, the Panel concluded that the food additive PEFA (E 475) was not of safety concern at the reported uses and use levels and that there was no need for a numerical ADI. The Panel recommended some modifications of the EU specifications for E 475.

Re-evaluation of oxidised starch (E 1404), monostarch phosphate (E 1410), distarch phosphate (E 1412), phosphated distarch phosphate (E 1413), acetylated distarch phosphate (E 1414), acetylated starch (E 1420), acetylated distarch adipate (E 1422), hydroxypropyl starch (E 1440), hydroxypropyl distarch phosphate (E 1442), starch sodium octenyl succinate (E 1450), acetylated oxidised starch (E 1451) and starch aluminium octenyl succinate (E 1452) as food additives

Following a request from the European Commission, the EFSA Panel on Food Additives and Nutrient sources added to Food (ANS) was asked to deliver a scientific opinion on the re-evaluation of 12 modified starches (E 1404, E 1410, E 1412, E 1413, E 1414, E 1420, E 1422, E 1440, E 1442, E 1450, E 1451 and E 1452) authorised as food additives in the EU in accordance with Regulation (EC) No 1333/2008 and previously evaluated by JECFA and the SCF. Both committees allocated an acceptable daily intake (ADI) 'not specified'. In humans, modified starches are not absorbed intact but significantly hydrolysed by intestinal enzymes and then fermented by the intestinal microbiota. Using the read-across approach, the Panel considered that adequate data on short- and long-term toxicity and carcinogenicity, and reproductive toxicity are available. Based on in silico analyses, modified starches are considered not to be of genotoxic concern. No treatment-related effects relevant for human risk assessment were observed in rats fed very high levels of modified starches (up to 31,000 mg/kg body weight (bw) per day). Modified starches (e.g. E 1450) were well tolerated in humans up to a single dose of 25,000 mg/person. Following the conceptual framework for the risk assessment of certain food additives, the Panel concluded that there is no safety concern for the use of modified starches as food additives at the reported uses and use levels for the general population and that there is no need for a numerical ADI. The combined exposure to E 1404-E 1451 at the 95th percentile of the refined (brand-loyal) exposure assessment scenario for the general population was up to 3,053 mg/kg bw per day. Exposure to E 1452 for food supplement consumers only at the 95th percentile was up to 22.1 mg/kg bw per day.

Re-evaluation of xanthan gum (E 415) as a food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of xanthan gum (E 415) as food additive. Following the conceptual framework for the risk assessment of certain food additives re‐evaluated under Commission Regulation (EU) No 257/2010, the Panel considered that adequate exposure and toxicity data were available. Based on the reported use levels, a refined exposure of up to 64 mg/kg bw per day in children for the general population, 38 mg/kg bw per day for children consumers only of food supplements at the high level exposure and 115 mg/kg bw per day for infants consuming foods for special medical purposes and special formulae (FSMPs), were estimated. Xanthan gum (E 415) is unlikely to be absorbed intact and is expected to be fermented by intestinal microbiota. No adverse effects were reported at the highest doses tested in chronic and carcinogenicity studies and there is no concern with respect to the genotoxicity. Repeated oral intake by adults of xanthan gum up to 214 mg/kg bw per day for ten days was well tolerated, but some individuals experienced abdominal discomfort, an undesirable but not adverse effect. The Panel concluded that there is no need for a numerical ADI for xanthan gum (E 415), and that there is no safety concern for the general population at the refined exposure assessment of xanthan gum (E 415) as food additive. Considering the outcome of clinical studies and post‐marketing surveillance, the Panel concluded that there is no safety concern from the use of xanthan gum (E 415) in FSMPs for infants and young children at concentrations reported by the food industry. The current re‐evaluation of xanthan gum (E 415) as a food additive is not considered to be applicable for infants under the age of 12 weeks.

Re-evaluation of sorbitan monostearate (E 491), sorbitan tristearate (E 492), sorbitan monolaurate (E 493), sorbitan monooleate (E 494) and sorbitan monopalmitate (E 495) when used as food additives

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re-evaluating the safety of sorbitan monostearate (E 491), sorbitan tristearate (E 492), sorbitan monolaurate (E 493), sorbitan monooleate (E 494) and sorbitan monopalmitate (E 495) when used as food additives. The Scientific Committee on Food (SCF) allocated an acceptable daily intake (ADI) of 25 mg/kg body weight (bw) per day for E 491, E 492 and E 495 singly or in combination; and a separate group ADI for E 493 and E 494 singly or in combination of 5 mg/kg bw per day calculated as sorbitan monolaurate in 1974. The Panel noted that after oral administration sorbitan monostearate can be either hydrolysed to its fatty acid moiety and the corresponding anhydrides of sorbitol and excreted via urine or exhaled as CO 2 or excreted intact in the faeces. The Panel considered that sorbitan esters did not raise concern for genotoxicity. Based on the no observed adverse effect level (NOAEL) of 2,600 mg sorbitan monostearate/kg bw per day, taking into account the ratio between the molecular weight of sorbitan monostearate (430.62 g/mol) and sorbitan (164.16 g/mol), and applying an uncertainty factor of 100, the Panel derived a group ADI of 10 mg/kg bw per day expressed as sorbitan for sorbitan esters (E 491-495) singly or in combination. This group ADI of 10 mg sorbitan/kg bw per day is equivalent to 26 mg sorbitan monostearate/kg bw per day. The Panel concluded that the exposure at the mean and the 95th percentile level, using non-brand-loyal scenario, did not exceed the ADI in any of the population groups. The Panel on the request for an amendment of specifications regarding the removal of 'congealing range' concluded that it could be eventually replaced by another identification parameter such as melting point.

Re-evaluation of polyglycerol polyricinoleate (E 476) as a food additive

The Panel on Food Additives and Nutrient Sources added to Food (ANS) provides a scientific opinion re‐evaluating the safety of polyglycerol polyricinoleate (PGPR, E 476) used as a food additive. In 1978, the Scientific Committee for Food (SCF) established an acceptable daily intake (ADI) of 7.5 mg/kg body weight (bw) per day for PGPR. PGPR is hydrolysed in the gut resulting in the liberation of free polyglycerols, polyricinoleic acid and ricinoleic acid. Di‐ and triglycerol are absorbed and excreted unchanged in the urine; long‐chain polyglycerols show lower absorption and are mainly excreted unchanged in faeces. Acute oral toxicity of PGPR is low, and short‐term and subchronic studies indicate PGPR is tolerated at high doses without adverse effects. PGPR (E 476) is not of concern with regard to genotoxicity or carcinogenicity. The single reproductive toxicity study with PGPR was limited and was not an appropriate study for deriving a health‐based guidance value. Human studies with PGPR demonstrated that there is no indication of significant adverse effect. The Panel considered a 2‐year combined chronic toxicity/carcinogenicity study for determining a reference point and derived a no observed adverse effect level (NOAEL) for PGPR (E 476) of 2,500 mg/kg bw per day, the only dose tested. Therefore, the Panel concluded that the present data set give reason to revise the ADI of 7.5 mg/kg bw per day allocated by SCF to 25 mg/kg bw per day. Exposure estimates did not exceed the ADI of 25 mg/kg bw per day and a proposed extension of use would not result in an exposure exceeding this ADI. The Panel recommended modification of the EU specifications for PGPR (E 476).

In silico exploratory study using structure-activity relationship models and metabolic information for prediction of mutagenicity based on the Ames test and rodent micronucleus assay

The mutagenic potential of chemicals is a cause of growing concern, due to the possible impact on human health. In this paper we have developed a knowledge-based approach, combining information from structure-activity relationship (SAR) and metabolic triggers generated from the metabolic fate of chemicals in biological systems for prediction of mutagenicity in vitro based on the Ames test and in vivo based on the rodent micronucleus assay. In the first part of the work, a model was developed, which comprises newly generated SAR rules and a set of metabolic triggers. These SAR rules and metabolic triggers were further externally validated to predict mutagenicity in vitro, with metabolic triggers being used only to predict mutagenicity of chemicals, which were predicted unknown, by SARpy. Hence, this model has a higher accuracy than the SAR model, with an accuracy of 89% for the training set and 75% for the external validation set. Subsequently, the results of the second part of this work enlist a set of metabolic triggers for prediction of mutagenicity in vivo, based on the rodent micronucleus assay. Finally, the results of the third part enlist a list of metabolic triggers to find similarities and differences in the mutagenic response of chemicals in vitro and in vivo.

Evaluation of the mutagenicity of simple substituted quinoxalines in Salmonella typhimurium

Limited information is available on the genotoxicity of simple quinoxalines, distinct from the food related carcinogenic derivatives bearing an aromatic amino group. Isolated positive results, with no apparent structure-activity relationships, were reported in earlier studies on alkyl substituted quinoxalines, raising a safety concern in some regulatory authorities in view of the potential human exposure related to their use as food flavors. In order to elucidate the genotoxic hazard posed by simple quinoxalines, in this work a random set of mono- and bi-substituted methyl, chloro- and hydroxyl- quinoxalines have been tested in an OECD-compliant bacterial reversion test (TG 471). The results obtained do not highlight any genotoxic potential in the set of quinoxalines examined, and suggest that this may be a common trait for other simple substituted quinoxalines. Earlier published positive findings were not confirmed in this work, which call for a cautious approach in the use of literature data for regulatory purpose.

A Review on Mutagenicity Testing for Hazard Classification of Chemicals at Work: Focusing on in vivo Micronucleus Test for Allyl Chloride

Chemical mutagenicity is a major hazard that is important to workers' health. Despite the use of large amounts of allyl chloride, the available mutagenicity data for this chemical remains controversial. To clarify the mutagenicity of allyl chloride and because a micronucleus (MN) test had not yet been conducted, we screened for MN induction by using male ICR mice bone marrow cells. The test results indicated that this chemical is not mutagenic under the test conditions. In this paper, the regulatory test battery and several assay combinations used to determine the genotoxic potential of chemicals in the workplace have been described. Further application of these assays may prove useful in future development strategies of hazard evaluations of industrial chemicals. This study also should help to improve the testing of this chemical by commonly used mutagenicity testing methods and investigations on the underlying mechanisms and could be applicable for workers' health.

Progress in computational toxicology

INTRODUCTION

Computational methods have been widely applied to toxicology across pharmaceutical, consumer product and environmental fields over the past decade. Progress in computational toxicology is now reviewed.

METHODS

A literature review was performed on computational models for hepatotoxicity (e.g. for drug-induced liver injury (DILI)), cardiotoxicity, renal toxicity and genotoxicity. In addition various publications have been highlighted that use machine learning methods. Several computational toxicology model datasets from past publications were used to compare Bayesian and Support Vector Machine (SVM) learning methods.

RESULTS

The increasing amounts of data for defined toxicology endpoints have enabled machine learning models that have been increasingly used for predictions. It is shown that across many different models Bayesian and SVM perform similarly based on cross validation data.

DISCUSSION

Considerable progress has been made in computational toxicology in a decade in both model development and availability of larger scale or 'big data' models. The future efforts in toxicology data generation will likely provide us with hundreds of thousands of compounds that are readily accessible for machine learning models. These models will cover relevant chemistry space for pharmaceutical, consumer product and environmental applications.

Mutagenicity, carcinogenicity, and other end points

Aiming at understanding the structural and physical chemical basis of the biological activity of chemicals, the science of structure-activity relationships has seen dramatic progress in the last decades. Coarse-grain, qualitative approaches (e.g., the structural alerts), and fine-tuned quantitative structure-activity relationship models have been developed and used to predict the toxicological properties of untested chemicals. More recently, a number of approaches and concepts have been developed as support to, and corollary of, the structure-activity methods. These approaches (e.g., chemical relational databases, expert systems, software tools for manipulating the chemical information) have dramatically expanded the reach of the structure-activity work; at present, they are powerful and inescapable tools for computer chemists, toxicologists, and regulators. This chapter, after a general overview of traditional and well-known approaches, gives a detailed presentation of the latter more recent support tools freely available in the public domain.

Simulation of chemical metabolism for fate and hazard assessment. V. Mammalian hazard assessment

Animals and humans are exposed to a wide array of xenobiotics and have developed complex enzymatic mechanisms to detoxify these chemicals. Detoxification pathways involve a number of biotransformations, such as oxidation, reduction, hydrolysis and conjugation reactions. The intermediate substances created during the detoxification process can be extremely toxic compared with the original toxins, hence metabolism should be accounted for when hazard effects of chemicals are assessed. Alternatively, metabolic transformations could detoxify chemicals that are toxic as parents. The aim of the present paper is to describe specificity of eukaryotic metabolism and its simulation and incorporation in models for predicting skin sensitization, mutagenicity, chromosomal aberration, micronuclei formation and estrogen receptor binding affinity implemented in the TIMES software platform. The current progress in model refinement, data used to parameterize models, logic of simulating metabolism, applicability domain and interpretation of predictions are discussed. Examples illustrating the model predictions are also provided.

Toxicopathological effects of lambda-cyhalothrin in female rabbits (Oryctolagus cuniculus)

The aim of this study was to investigate effects of lambda-cyhalothrin (LCT) on clinical, hematological, biochemical and pathological alterations in rabbits (Oryctolagus cuniculus). New Zealand white female rabbits (n = 24) of 4-5 months age having 997.92 ± 32.83 g weight were divided into four equal groups. Group A (control) received normal saline intraperitoneally (ip). Animals in groups B, C and D were treated with LCT 1.0, 4.0 and 8.0 mg/kg bw ip. Each group received seven consecutive doses at an interval of 48 hours. Blood and serum samples were collected at an interval of 96 hours. Blood analysis revealed a significant (p < 0.05) decrease in red blood cell and white blood cell counts, hemoglobin concentration and lymphocytes, while mean corpuscular hemoglobin concentration, mean corpuscular volume, neutrophils, monocytes and eosinophils were increased. Serum biochemical analysis revealed significant (p < 0.05) decrease in serum total proteins and serum albumin, while an increase was seen in serum alanine aminotransferase and aspartate aminotransferase activities compared with the control group. Serum globulin values varied non-significantly in all treatment groups as compared to control group. A dose-dependent increase in the incidence of micronucleated polychromatic erythrocyte was observed. All gross and histopathological lesions observed in LCT-treated rabbits were dose-dependent. Liver of the treated rabbits exhibited extensive perihepatitis, hyperplasia of bile duct, necrosis, hemorrhages and congestion. In lungs, there were hemorrhages, thickened alveolar walls, congestion, emphysema, collapsed alveoli and accumulation of extensive inflammatory cells. Kidneys were congested and hemorrhagic whereas renal parenchyma and stroma were normal. Microscopically, heart showed congestion of blood vessels and nuclear pyknosis, myodegeneration. It was concluded from the study that LCT produced toxicopathological alterations in rabbits in a dose-dependent manner. On the basis of the results, it can be suggested that overdosing of LCT be avoided while treating animals for ectoparasites.