Towards a mechanism-based approach for the prediction of nongenotoxic carcinogenic potential of agrochemicals.

Chemical substances are subjected to assessment of genotoxic and carcinogenic effects before being marketed to protect man and the environment from health risks. For agrochemicals, the long-term rodent carcinogenicity study is currently required from a regulatory perspective. Although it is the current mainstay for the detection of nongenotoxic carcinogens, carcinogenicity studies are shown to have prominent weaknesses and are subject to ethical and scientific debate. A transition toward a mechanism-based weight-of-evidence approach is considered a requirement to enhance the prediction of carcinogenic potential for environmental (agro)chemicals. The resulting approach should make optimal use of innovative (computational) tools and be less animal demanding. To identify the various mode of actions (MOAs) underlying the nongenotoxic carcinogenic potential of agrochemicals, we conducted an extensive analysis of 411 unique agrochemicals that have been evaluated for carcinogenicity by the United States Environmental Protection Agency (US EPA) and the European Chemicals Agency (ECHA). About one-third of these substances could be categorized as nongenotoxic carcinogens with an average of approximately two tumor types per substance, observed in a variety of organs. For two-third of the tumor cases, an underlying MOA (network) could be identified. This analysis demonstrates that a limited set of MOA (networks) is underlying nongenotoxic carcinogenicity of agrochemicals, illustrating that the transition toward a MOA-driven approach appears manageable. Ultimately the approach should cover relevant MOAs and its associated key events; this will also facilitate the evaluation of the human relevance. This manuscript describes the results of the analysis while identifying knowledge gaps and necessities to achieve a mechanism-based weight-of-evidence approach.

A comprehensive view on mechanistic approaches for cancer risk assessment of non-genotoxic agrochemicals.

Currently the only methods for non-genotoxic carcinogenic hazard assessment accepted by most regulatory authorities are lifetime carcinogenicity studies. However, these involve the use of large numbers of animals and the relevance of their predictive power and results has been scientifically challenged. With increased availability of innovative test methods and enhanced understanding of carcinogenic processes, it is believed that tumour formation can now be better predicted using mechanistic information. A workshop organised by the European Partnership on Alternative Approaches to Animal Testing brought together experts to discuss an alternative, mechanism-based approach for cancer risk assessment of agrochemicals. Data from a toolbox of test methods for detecting modes of action (MOAs) underlying non-genotoxic carcinogenicity are combined with information from subchronic toxicity studies in a weight-of-evidence approach to identify carcinogenic potential of a test substance. The workshop included interactive sessions to discuss the approach using case studies. These showed that fine-tuning is needed, to build confidence in the proposed approach, to ensure scientific correctness, and to address different regulatory needs. This novel approach was considered realistic, and its regulatory acceptance and implementation can be facilitated in the coming years through continued dialogue between all stakeholders and building confidence in alternative approaches.

Is current risk assessment of non-genotoxic carcinogens protective?

Non-genotoxic carcinogens (NGTXCs) do not cause direct DNA damage but induce cancer via other mechanisms. In risk assessment of chemicals and pharmaceuticals, carcinogenic risks are determined using carcinogenicity studies in rodents. With the aim to reduce animal testing, REACH legislation states that carcinogenicity studies are only allowed when specific concerns are present; risk assessment of compounds that are potentially carcinogenic by a non-genotoxic mode of action is usually based on subchronic toxicity studies. Health-based guidance values (HBGVs) of NGTXCs may therefore be based on data from carcinogenicity or subchronic toxicity studies depending on the legal framework that applies. HBGVs are usually derived from No-Observed-Adverse-Effect-Levels (NOAELs). Here, we investigate whether current risk assessment of NGTXCs based on NOAELs is protective against cancer. To answer this question, we estimated Benchmark doses (BMDs) for carcinogenicity data of 44 known NGTXCs. These BMDs were compared to the NOAELs derived from the same carcinogenicity studies, as well as to the NOAELs derived from the associated subchronic studies. The results lead to two main conclusions. First, a NOAEL derived from a subchronic study is similar to a NOAEL based on cancer effects from a carcinogenicity study, supporting the current practice in REACH. Second, both the subchronic and cancer NOAELs are, on average, associated with a cancer risk of around 1% in rodents. This implies that for those chemicals that are potentially carcinogenic in humans, current risk assessment of NGTXCs may not be completely protective against cancer. Our results call for a broader discussion within the scientific community, followed by discussions among risk assessors, policy makers, and other stakeholders as to whether or not the potential cancer risk levels that appear to be associated with currently derived HBGVs of NGXTCs are acceptable.

Integrating in vitro data and physiologically based kinetic (PBK) modelling to assess the in vivo potential developmental toxicity of a series of phenols.

Toxicity outcomes derived in vitro do not always reflect in vivo toxicity values, which was previously observed for a series of phenols tested in the embryonic stem cell test (EST). Translation of in vitro data to the in vivo situation is therefore an important, but still limiting step for the use of in vitro toxicity outcomes in the safety assessment of chemicals. The aim of the present study was to translate in vitro embryotoxicity data for a series of phenols to in vivo developmental toxic potency values for the rat by physiologically based kinetic (PBK) modelling-based reverse dosimetry. To this purpose, PBK models were developed for each of the phenols. The models were parameterised with in vitro-derived values defining metabolism and transport of the compounds across the intestinal and placental barrier and with in silico predictions and data from the literature. Using PBK-based reverse dosimetry, in vitro concentration-response curves from the EST were translated into in vivo dose-response curves from which points of departure (PoDs) were derived. The predicted PoDs differed less than 3.6-fold from PoDs derived from in vivo toxicity data for the phenols available in the literature. Moreover, the in vitro PBK-based reverse dosimetry approach could overcome the large disparity that was observed previously between the in vitro and the in vivo relative potency of the series of phenols. In conclusion, this study shows another proof-of-principle that the in vitro PBK approach is a promising strategy for non-animal-based safety assessment of chemicals.

The Isolated Chicken Eye test to replace the Draize test in rabbits.

In 1944, Draize et al., published a paper entitled "Methods for the study of irritation and toxicity of substances applied topically to the skin and mucous membranes". The Organization for Economic Co-operation and Development published their first guideline on eye irritation in 1981, using rabbits. In the early eighties the development of alternative non-animal tests to replace the Draize eye test started. The first attempts to validate alternative tests for eye irritation were considered to be relatively simple by comparing in vitro and in vivo irritation index scores. In the early nineteen-eighties, we introduced the use of isolated eyes as an alternative test for the Draize eye irritation test. What was expected to be a process of several years, however, turned out to be a decades spanning process still not fully completed. For a large part, this can be attributed to the nature of the in vivo test in rabbits, which is more complicated and compromised than originally believed. This paper describes, most chronologically, the development, performance, validation and application of the Isolated Eye Test and, in broader perspective, the international validation and acceptance of this alternative test by regulatory authorities and agencies.

An integrative test strategy for cancer hazard identification.

Assessment of genotoxic and carcinogenic potential is considered one of the basic requirements when evaluating possible human health risks associated with exposure to chemicals. Test strategies currently in place focus primarily on identifying genotoxic potential due to the strong association between the accumulation of genetic damage and cancer. Using genotoxicity assays to predict carcinogenic potential has the significant drawback that risks from non-genotoxic carcinogens remain largely undetected unless carcinogenicity studies are performed. Furthermore, test systems already developed to reduce animal use are not easily accepted and implemented by either industries or regulators. This manuscript reviews the test methods for cancer hazard identification that have been adopted by the regulatory authorities, and discusses the most promising alternative methods that have been developed to date. Based on these findings, a generally applicable tiered test strategy is proposed that can be considered capable of detecting both genotoxic as well as non-genotoxic carcinogens and will improve understanding of the underlying mode of action. Finally, strengths and weaknesses of this new integrative test strategy for cancer hazard identification are presented.

Prediction of carcinogenic potential of chemicals using repeated-dose (13-week) toxicity data.

Sub-chronic toxicity studies of 163 non-genotoxic chemicals were evaluated in order to predict the tumour outcome of 24-month rat carcinogenicity studies obtained from the EFSA and ToxRef databases. Hundred eleven of the 148 chemicals that did not induce putative preneoplastic lesions in the sub-chronic study also did not induce tumours in the carcinogenicity study (True Negatives). Cellular hypertrophy appeared to be an unreliable predictor of carcinogenicity. The negative predictivity, the measure of the compounds evaluated that did not show any putative preneoplastic lesion in de sub-chronic studies and were negative in the carcinogenicity studies, was 75%, whereas the sensitivity, a measure of the sub-chronic study to predict a positive carcinogenicity outcome was only 5%. The specificity, the accuracy of the sub-chronic study to correctly identify non-carcinogens was 90%. When the chemicals which induced tumours generally considered not relevant for humans (33 out of 37 False Negatives) are classified as True Negatives, the negative predictivity amounts to 97%. Overall, the results of this retrospective study support the concept that chemicals showing no histopathological risk factors for neoplasia in a sub-chronic study in rats may be considered non-carcinogenic and do not require further testing in a carcinogenicity study.

Predicting individual responses to pravastatin using a physiologically based kinetic model for plasma cholesterol concentrations.

We used a previously developed physiologically based kinetic (PBK) model to analyze the effect of individual variations in metabolism and transport of cholesterol on pravastatin response. The PBK model is based on kinetic expressions for 21 reactions that interconnect eight different body cholesterol pools including plasma HDL and non-HDL cholesterol. A pravastatin pharmacokinetic model was constructed and the simulated hepatic pravastatin concentration was used to modulate the reaction rate constant of hepatic free cholesterol synthesis in the PBK model. The integrated model was then used to predict plasma cholesterol concentrations as a function of pravastatin dose. Predicted versus observed values at 40 mg/d pravastatin were 15 versus 22 % reduction of total plasma cholesterol, and 10 versus 5.6 % increase of HDL cholesterol. A population of 7,609 virtual subjects was generated using a Monte Carlo approach, and the response to a 40 mg/d pravastatin dose was simulated for each subject. Linear regression analysis of the pravastatin response in this virtual population showed that hepatic and peripheral cholesterol synthesis had the largest regression coefficients for the non-HDL-C response. However, the modeling also showed that these processes alone did not suffice to predict non-HDL-C response to pravastatin, contradicting the hypothesis that people with high cholesterol synthesis rates are good statin responders. In conclusion, we have developed a PBK model that is able to accurately describe the effect of pravastatin treatment on plasma cholesterol concentrations and can be used to provide insight in the mechanisms behind individual variation in statin response.

Risk assessment of feed components of botanical origin - Approaches taken in the European Union.

In view of a continuous trend in replacing synthetic feed additives and especially flavouring compounds by botanical preparations, different aspects of the safety evaluations of plants and plant-derived preparations and components in feed are discussed. This includes risk assessment approaches developed by the European Food Safety Authority (EFSA) for phytotoxins regarding unintentional exposure of target animals and of consumers to animal derived food via carry-over from feed. Relevant regulatory frameworks for feed additives and feed contaminants in the European Union are summarised and the essentials of existing guidelines used in the safety evaluation of botanicals and their preparations and components in feed are outlined. The examples presented illustrate how the safety of the botanicals, their preparations and components present in feed is assessed. An outlook on possible future developments in risk assessment by applying new in vitro and in silico methodologies is given.

Safety of a feed additive consisting of endo 1,4 ß-d-mannanase produced by Thermothelomyces thermophilus DSM 33149 (Natupulse® TS/TS L) for chickens and turkeys for fattening, minor poultry species for fattening and ornamental birds (BASF SE).

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 of a feed additive consisting of endo-1,4-ß-d-mannanase produced by Thermothelomyces thermophilus DSM 33149, intended for use as a zootechnical additive (functional group: digestibility enhancers) for chickens for fattening, turkeys for fattening, minor poultry species for fattening and ornamental birds. The safety and efficacy of the additive have been already assessed previously; however, the FEEDAP Panel could not conclude on the safety of the additive for the target species, consumers and the users due to lack of reliable data on the potential genotoxicity of the additive. In the present assessment, the applicant submitted a new in vitro mammalian cell micronucleus test. After the assessment of the data newly submitted, the FEEDAP Panel concluded that the use of the feed additive in animal nutrition under the conditions of use proposed is of no concern for target species and consumer safety. The additive is not irritant to the eyes or skin. Owing to the proteinaceous nature of the active substance, the additive should be considered a respiratory sensitiser. The Panel cannot conclude on the potential of the additive to be a skin sensitiser.

Assessment of the feed additive consisting of Lentilactobacillus buchneri (formerly Lactobacillus buchneri) DSM 22501 for all animal species for the renewal of its authorisation (Chr. Hansen A/S).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the assessment of the application for renewal of the authorisation of the additive consisting of Lentilactobacillus buchneri DSM 22501 as a technological feed additive to improve ensiling of fresh material for all animal species. The applicant has provided evidence that the additive currently on the market complies with the existing conditions of authorisation. There is no new evidence that would lead the FEEDAP Panel to reconsider its previous conclusions. Thus, the Panel concludes that the additive remains safe for all animal species, consumer and the environment under the authorised conditions of use. Regarding user safety, the additive is not irritant to skin and eye, but owing to its proteinaceous nature it should be considered a respiratory sensitiser. No conclusions could be drawn on the skin sensitisation potential of the additive. There is no need for assessing the efficacy of the additive in the context of the renewal of the authorisation.

Safety of feed additives consisting of microcrystalline cellulose and carboxymethyl cellulose for all animal species (International Cellulosics Association).

Following a request from the European Commission, the EFSA Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) was asked to deliver a scientific opinion on the safety of microcrystalline cellulose and carboxymethyl cellulose as technological feed additives for all animal species. In its previous opinions on the safety and efficacy of the products, the FEEDAP Panel could not conclude on proper identification and characterisation as required for a feed additive. The occurrence of potential toxic impurities could also not be assessed. Based on the new data provided, the feed additives microcrystalline cellulose and carboxymethyl cellulose were properly identified and characterised and were shown to meet the specifications set for their use as food additives. Therefore, the conclusions of the safety reached in the previous opinions for microcrystalline cellulose and carboxymethyl cellulose meeting the food additive specifications apply to the microcrystalline cellulose and carboxymethyl cellulose under assessment as feed additives. The additives are considered safe for all animal species, the consumer and the environment. In the absence of data, the FEEDAP Panel is not in the position to conclude on the safety for the user.

Efficacy of a feed additive consisting of carvacrol (Nimicoat®) for weaned piglets (Techna France Nutrition).

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 efficacy of a feed additive consisting of carvacrol (Nimicoat®) as a zootechnical feed additive for weaned piglets at the recommended use level of 250 mg/kg complete feed. In a previous assessment, three efficacy trials and one tolerance-efficacy trial were assessed. Only one of the efficacy trials was considered to support the efficacy at the recommended use level. The applicant provided amendments to two previously submitted studies and a new trial. The amendments to the previously submitted studies did not change the conclusions from the previous assessment. The new efficacy study showed a significant improvement of the zootechnical parameters. Two studies showed positive and significant effects on the performance of the weaned piglets when the additive was administered at 250 mg/kg feed. Due to the lack of sufficient data, the FEEDAP Panel is not in the position to conclude on the efficacy of the additive for the target species.

Assessment of the feed additive consisting of Bacillus velezensisATCC PTA-6737 (PB6) for turkeys for fattening and turkeys reared for breeding for the renewal of its authorisation and the modification of the conditions of the authorisation for other growing poultry species (Kemin Europe N.V).

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 Bacillus velezensis ATCC PTA-6737 as a zootechnical additive (functional group: gut-flora stabiliser) in the context of the renewal of the authorisation for turkeys for fattening and turkeys reared for breeding. The applicant is also requesting to modify the target species in the current authorisations to 'all growing poultry', the increase of the recommended use level in chickens for fattening, chickens reared for laying and minor poultry species except minor poultry for laying from 1 × 107 to 1 × 108 CFU/kg complete feed and the compatibility of the additive with halofuginone. The applicant provided evidence that the additive currently in the market complies with the conditions of the authorisation. There was no new evidence that would lead to reconsider previous conclusions. Therefore, the FEEDAP Panel concluded that the additive remains safe for all poultry species for fattening and reared for laying/breeding, the consumers and the environment under the current authorised conditions of use. The additive is not irritant to the skin and eyes, but it should be considered a respiratory sensitiser. The Panel could not conclude on the skin sensitisation potential of the additive. The Panel concluded that the additive has a potential to be efficacious as a zootechnical additive for poultry for fattening and reared for laying/breeding under the proposed conditions of use.

Safety and efficacy of a feed additive consisting of Enterococcus lactis NCIMB 11181 (Lactiferm®) for chickens for fattening or reared for laying, other poultry species for fattening or reared for laying, and ornamental birds (Chr. Hansen A/S).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of a feed additive consisting of Enterococcus lactis NCIMB 11181 (Lactiferm®) as a zootechnical additive (gut flora stabiliser) for chickens for fattening, chickens reared for laying, other poultry species for fattening or reared for laying, and ornamental birds. The additive is available in two formulations: Lactiferm WS200 and Lactiferm Basic 50. The FEEDAP Panel concluded that the use of the additive is safe for chickens for fattening or reared for laying, other poultry species for fattening or reared for laying, and ornamental birds. The Panel also concluded that the use of the feed additive is safe for consumers, and the environment. Lactiferm WS200 is not irritant to skin or eyes. Owing to the proteinaceous nature of the active agent, both formulations of the additive are considered respiratory sensitisers. It was not possible, however, to conclude on the irritancy potential for skin and eyes of the Lactiferm Basic 50 formulation or on the potential of both formulations of the additive to cause skin sensitisation. The efficacy studies submitted did not allow to draw a conclusion on the efficacy of the additive for the target species. Lactiferm® is considered compatible with the coccidiostats monensin sodium and decoquinate.

Safety and efficacy of a feed additive consisting of Bacillus velezensis ATCC PTA-6737 (PB6) for the renewal of the authorisations in weaned piglets, weaned minor porcine species and sows and the extension of use to all Suidae (Kemin Europe N.V).

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 Bacillus velezensis ATCC PTA-6737 as a zootechnical additive (functional group: gut flora stabilisers) in regard to the renewal of the authorisation for weaned piglets, weaned minor porcine species, sows and minor reproductive Suidae species, and its extension of use for all Suidae. The applicant provided evidence that the additive currently in the market complies with the conditions of the authorisation. The Panel concluded that there is no new evidence that would lead it to reconsider the previous conclusions; the additive is safe for the target species, consumers and the environment under the authorised conditions of use. This conclusion also applies to the target species/categories for which a request for an extension of use is made. The Panel concluded that B. velezensis ATCC PTA-6737 is not irritant to skin or eyes but should be considered a respiratory sensitiser due to its proteinaceous nature. No conclusions could be drawn on the skin sensitisation potential of the additive. The Panel concluded that the additive has the potential to be efficacious in all growing Suidae (suckling, weaned and fattening Suidae) at the minimum inclusion level of 1 × 107 CFU/kg of complete feed and in sows and minor reproductive Suidae species at 1 × 108 CFU/kg complete feed.

Consumer safety of feed additives containing selenium.

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety for the consumer of products from animals fed diets with feed additives containing selenium as an active substance. Based on the limited data set available and the several uncertainties, the FEEDAP Panel concluded that the use of organic selenium at the currently maximum authorised use level of 0.2 mg supplemented selenium from organic sources/kg complete feed (within a maximum of 0.5 mg total selenium/kg complete feed) leads to an exceedance of the UL for all the population categories (except elderly and very elderly), suggesting a concern for consumer safety. It was not possible to conclude on the safety of the currently maximum use level of 0.5 mg total selenium/kg complete feed for all consumer categories. Additional data from studies specifically designed to measure deposition of selenium in tissues and products from animal origin resulting from the use of the different sources of selenium would be required to perform a proper risk assessment.

Efficacy of a feed additive consisting of Saccharomyces cerevisiae DBVPG 48 SF (BioCell®) for ruminants (Mazzoleni S.p.A.).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the safety and efficacy of Saccharomyces cerevisiae DBVPG 48 SF (BioCell®) as a zootechnical feed additive for horses, pigs and ruminants. In a previous opinion, the Panel on Additives and Products or Substances used in Animal Feed (FEEDAP) concluded that the additive has the potential to be efficacious at the proposed conditions of use for horses, dairy ruminants and all pigs. However, the Panel was not in the position to conclude on the efficacy of BioCell® for calves, and, consequently, for other ruminants for fattening or rearing. The applicant provided three additional efficacy trials in veal calves to support the efficacy of BioCell® for ruminants for fattening or rearing. The three studies showed positive effects of the supplementation with the additive at 1.7 × 109 colony forming unit (CFU)/kg complete feed on the performance of veal calves. Considering the previously submitted studies in dairy cows and the new submitted trials, the FEEDAP Panel concluded that the additive has the potential to be efficacious for all ruminants at the proposed condition of use: 4.0 × 108 CFU/kg complete feed for dairy ruminants and 4.0 × 109 CFU/kg complete feed for ruminants for fattening and rearing.

Efficacy of the feed additive consisting of Saccharomyces cerevisiae CNCM I-4407 (Actisaf® Sc47) for cattle for fattening (Lesaffre International).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the efficacy of Saccharomyces cerevisiae CNCM I-4407 (Actisaf® Sc47) as a zootechnical feed additive (functional group: gut flora stabiliser) in cattle for fattening. The additive is already authorised for use in feed for dairy cows, calves for rearing, lambs for fattening, dairy goats, dairy sheep and dairy buffaloes. In a previous opinion, the EFSA Scientific Panel on Additives and Products or Substances used in Animal Feed (FEEDAP Panel) concluded that Actisaf® Sc47 was safe for cattle for fattening, the consumers and the environment. Additionally, the Panel considered that Actisaf® Sc47 is not a skin irritant, and no conclusions could be drawn on the additive's eye irritancy and dermal sensitisation potential. Due to the lack of adequate data, the Panel could not conclude on the efficacy of the additive in cattle for fattening at the proposed conditions of use. In the current application, the applicant submitted three trials to support the efficacy in cattle for fattening. However, two of them were not considered for the assessment. The other trial showed an improved zootechnical performance of the animals at the proposed use level of 4 × 109 CFU/kg complete feed. Considering the additive is authorised in dairy cows and calves for rearing and the requirements of the current Guidance on the assessment of the efficacy of feed additives, no further demonstration of efficacy is necessary to extrapolate the conclusions previously reached to all ruminants. The significant positive effect shown in one trial in cattle for fattening supports the above extrapolation. Therefore, the FEEDAP Panel concludes that Actisaf® Sc47 is efficacious as a zootechnical additive for cattle for fattening at the proposed conditions of use.

Assessment of the feed additive consisting of Pediococcus pentosaceus DSM 14021 for all animal species for the renewal of its authorisation (Chr. Hansen A/S).

Following a request from the European Commission, EFSA was asked to deliver a scientific opinion on the assessment of the application for renewal of Pediococcus pentosaceus DSM 14021, a technological additive for all animal species. The applicant has provided evidence that the additive currently on the market complies with the existing conditions of authorisation. The Panel concluded that the additive remains safe for all animal species, consumers and the environment under the authorised conditions of use. Regarding user safety, the Panel considers that any exposure through skin and respiratory tract is considered a risk. The Panel cannot conclude on the eye irritation potential of the additive due to the lack of data. There is no need for assessing the efficacy of the additive in the context of the renewal of the authorisation.