Hazard identification by methods of animal-based toxicology

Assessing Optimal Cell Counts in Sperm Shape Abnormality Assays in Rodents

Rodents have been the preferred models for the evaluation of the toxicity of pollutants and drugs and their genotoxic effects, including sperm shape abnormalities. The scientific literature is dominated by studies conducted with model animals in laboratory conditions, but a generally accepted and standardized protocol addressing the optimal number of sperm cells to count is still lacking. In this study, we reviewed the literature regarding the number of counted sperm cells in such assessments, published from 1969 to 2023. To infer the number of counts providing the best cost/benefit regarding the robustness of the assay results, a new dataset involving the analysis of two populations of wild rodents was produced. We evaluated the frequency of sperm shape abnormalities in a total of 50 wild brown rats (Rattus norvegicus) captured in two port cities, aiming to detect the impact of differential sperm cell counts in the obtained results. During necropsy, the fresh epididymis tail of adult male rats was excised, and sperm cells were fixated in slides. For each animal, a total of 300, 500, 1000, and 2000 cells were sequentially counted, and head abnormalities were registered. Counting 300 sperm cells failed to detect significant differences between groups and 500 counts resulted in marginally significant differences. Only when 1000 or 2000 sperm cells were counted, significant differences emerged between groups. We propose that studies addressing sperm shape abnormalities should standardize counts to an optimal value of 1000 cells per animal, warranting robust statistical results while providing the best compromise concerning labor time.

Assessing dietary exposure risk to neonicotinoid residues among preschool children in regions of Taiwan

Neonicotinoids (NEOs) are a class of pesticides widely used worldwide. This study analyzed post-cooking residues of NEO pesticides and assessed their potential health risks for preschool children (0-6 years old) by conducting a total diet study (TDS). It involved food sampling, preparation, analysis of pesticide residues, estimation of food consumption data, and assessment of food safety risks. Food sampling was conducted between March and June 2015. A total of 128 food samples were obtained from 4 parts of Taiwan. After the food had been prepared, the 128 samples were aggregated into 32 composite food items and the NEO residues analyzed. Acetamiprid had the highest detection rate of the NEO residues (59.4%), and the concentrations ranged from not detected to 80.5 μg/kg. The estimated daily intake (EDI) of NEO residues among preschool children was found to be lower than the adjusted acceptable daily intake (ADI) even for highly exposed groups. The results showed that NEO pesticides were primarily detected in preserved fruits, cherry tomato, rape, bell fruit, and baby bok choy. The main health risk posed by detected NEO residues at high consumption rates for preschool children was attributed to acetamiprid (34.20 %ADI) and imidacloprid (23.69 %ADI), respectively. Therefore, this research implicates that the present level of NEO residues in the diets for preschool children in Taiwan does not exceed 100 %ADI.

A systematic literature review of fenugreek seed toxicity by using ToxRTool: evidence from preclinical and clinical studies

Fenugreek (Trigonella foenum graecum) seed extract is a bioactive ingredient of many food supplements. Hence, there is a need for systematic assessment of the quality of published toxicological studies for its use in human health, hazard consideration, and risk assessment. The aim of the present investigation was to determine the reliability of published toxicological studies of fenugreek seed by using ToxRTool (Toxicological data reliability assessment tool). A comprehensive systematic literature search was conducted in PubMed, EMBASE, Cochrane Library, CPCI-S, ICTRP, Ovid, and Google Scholar till October 2018. Each identified study was evaluated for its quality using the ToxRTool with outcomes such as combined score, weighted score, and reliability category by three independent raters. Correlations of various criteria groups with the combined score were evaluated by Pearson correlation and Kendall rank correlation coefficient. Inter-rater consistency was measured by Cronbach's alpha coefficient. The database searches initially yielded 436 results, of which 391 (89.67%) studies were “not assignable”. The remaining 45 studies were included for quantitative analysis by ToxRTool. Based on the weighted score, 17 in-vivo, and 3 in-vitro studies were determined to be “Reliable Without Restriction” which were conducted according to international guidelines such as GLP. These studies have a significant difference (p < 0.05) for the combined and weighted score as compared to non-GLP studies. Remaining 28 in-vivo and 2 in-vitro studies were determined to be “Not Reliable.” The GLP studies conducted with “identified study material” have a significant difference (p < 0.0001) between combined and weighted score as compared to studies which used “non-identified study material”. For criteria group of ToxRTool I, III and V, the Pearson correlation with the combined score was found to be 0.875, 0.734 and 0.905, respectively and Kendall rank correlation coefficient was found to be 0.764, 0.551 and 0.752, respectively. Cronbach's alpha coefficient for combined score and weighted score were 0.920 and 0.887, respectively. In conclusion, the ToxRTool was found useful to identify seventeen toxicity studies of fenugreek seeds as “Reliable without Restrictions”. These studies showed a broad margin of safety for the standardized extract of fenugreek seeds and can form a basis for toxicological risk assessment with reasonable certainty.

Spheroid-3D and Monolayer-2D Intestinal Electrochemical Biosensor for Toxicity/Viability Testing: Applications in Drug Screening, Food Safety, and Environmental Pollutant Analysis

The rise of three-dimensional cell culture systems that provide in vivo-like environments for pharmaco-toxicological models has prompted the need for simple and robust viability assays suitable for complex cell architectural structures. This study addresses that challenge with the development of an in vitro enzyme based electrochemical sensor for viability/cytotoxicity assessment of two-dimensional (2D) monolayer and three-dimensional (3D) spheroid culture formats. The biosensor measures the cell viability/toxicity via electrochemical monitoring of the enzymatic activity of nonspecific esterases of viable cells, through the hydrolysis of 1-naphthyl acetate to 1-naphthol. The proposed sensor demonstrated strong correlation ( r = 0.979) with viable cell numbers. Furthermore, the model intestinal toxicants diclofenac (DFC, pharmaceutical), okadaic acid (OA, food-safety), and mancozeb (MZB, environmental) were used for the functional evaluation of the proposed sensor using 2D and 3D culture formats. Sensor performance showed high consistency with conventional cell viability/cytotoxicity assays (MTT/CFDA-AM) for all toxicants, with the sensor IC₅₀ values matching the relevant viability LC₅₀ values at the 95% confidence interval range for 2D (DCF: 1.19-1.26 mM, MZB: 10.28-14.18 μM, OA: 40.91-77.13 nM) and 3D culture formats (DCF: 1.02-4.78 mM, MZB: 11.26-15.16 μM, OA: 162.09-179.67 nM). The presented results demonstrate the feasibility of the proposed sensor as a robust endpoint screening tool for both 2D and 3D cytotoxicity assessment.

Red meat and colon cancer: A review of mechanistic evidence for heme in the context of risk assessment methodology

On October 26, 2015, IARC published a summary of their findings regarding the association of cancer with consumption of red meat or processed meat (IARC 2015; The Lancet Oncology 2015). The Working Group concluded that there is limited evidence in human beings for carcinogenicity from the consumption of red meat and inadequate evidence in experimental animals for the carcinogenicity of consumption of red meat. Nevertheless, the working group concluded that there is strong mechanistic evidence by which ingestion of red meat can be linked to human colorectal cancer and assigned red meat to Group 2A "probably carcinogenic to humans". The Working Group cited supporting mechanistic evidence for multiple meat components, including those formed from meat processing, such as N-nitroso compounds (NOC) and heterocyclic aromatic amines, and the endogenous compound, heme iron. The mechanism of action for each of these components is different and so it is critical to evaluate the evidence for each component separately. Consequently, this review critically examined studies that investigated mechanistic evidence associated with heme iron to assess the weight of the evidence associating exposure to red meat with colorectal cancer. The evidence from in vitro studies utilized conditions that are not necessarily relevant for a normal dietary intake and thus do not provide sufficient evidence that heme exposure from typical red meat consumption would increase the risk of colon cancer. Animal studies utilized models that tested promotion of preneoplastic conditions utilizing diets low in calcium, high in fat combined with exaggerations of heme exposure that in many instances represented intakes that were orders of magnitude above normal dietary consumption of red meat. Finally, clinical evidence suggests that the type of NOC found after ingestion of red meat in humans consists mainly of nitrosyl iron and nitrosothiols, products that have profoundly different chemistries from certain N-nitroso species which have been shown to be tumorigenic through the formation of DNA adducts. In conclusion, the methodologies employed in current studies of heme have not provided sufficient documentation that the mechanisms studied would contribute to an increased risk of promotion of preneoplasia or colon cancer at usual dietary intakes of red meat in the context of a normal diet.

Safety Assessment of Food and Feed from GM Crops in Europe: Evaluating EFSA's Alternative Framework for the Rat 90-day Feeding Study

Regulatory-compliant rodent subchronic feeding studies are compulsory regardless of a hypothesis to test, according to recent EU legislation for the safety assessment of whole food/feed produced from genetically modified (GM) crops containing a single genetic transformation event (European Union Commission Implementing Regulation No. 503/2013). The Implementing Regulation refers to guidelines set forth by the European Food Safety Authority (EFSA) for the design, conduct, and analysis of rodent subchronic feeding studies. The set of EFSA recommendations was rigorously applied to a 90-day feeding study in Sprague-Dawley rats. After study completion, the appropriateness and applicability of these recommendations were assessed using a battery of statistical analysis approaches including both retrospective and prospective statistical power analyses as well as variance-covariance decomposition. In the interest of animal welfare considerations, alternative experimental designs were investigated and evaluated in the context of informing the health risk assessment of food/feed from GM crops.

Human BJ Fibroblasts is an Alternative to Mouse BALB/c 3T3 Cells in In Vitro Neutral Red Uptake Assay

The OECD GD 129 BALB/c 3T3 neutral red uptake (NRU) assay is a standardized test method for estimating starting dose for an acute oral systemic toxicity test in rodents. Mouse BALB/c 3T3 fibroblasts are the most commonly used cells in the NRU assay. We have previously transferred and validated BALB/c 3T3 NRU assay in our GLP laboratory. Subsequently, in order to obtain more human-relevant cytotoxicity data, we performed an intralaboratory validation using human BJ fibroblasts in the NRU assay instead of mouse BALB/c 3T3 fibroblasts. Here, we present comparative cytotoxicity data of 26 different test chemicals (pharmaceuticals, industrial chemicals, pesticides and food additives) produced with both BALB/c 3T3 NRU and BJ NRU assays.

An integrated approach to the safety assessment of food additives in early life

During the development of international standards by the Codex Alimentarius Commission, infant foods and their constituent ingredients are subject to rigorous risk analysis and are strictly regulated by many authorities. Various jurisdictions have approved only a limited number of additives specifically with regard to infant foods to fulfill specific technical requirements of quality. As part of the approval process, a rigorous safety assessment is essential to confirm that the use of additives does not pose any health risk for the consumer. An acceptable daily intake (ADI) may be derived from the toxicological databases. However, the ADI may not be applicable to infants because of the possible developmental sensitivities and potentially high exposure scenarios, leading to possible lower margins of safety than would often be determined for adult populations. There is interest in defining better food safety assessment approaches for pre-weaned infants aged less than 12–16 weeks. To confirm safe use in infants, we reviewed the suitability of the existing safety databases of six additives with historical uses in infant nutrition products. To determine further toxicity testing strategies, it is necessary to understand whether the chemical used in the additives is identical to endogenous physiological metabolites and/or whether immature organs of infants are targets of toxicity. Combined with an in-depth review of the existing relevant toxicological and nutritional studies, this integrated approach will facilitate decision-making. We propose a decision tree as a tool within this approach to help guide appropriate data requirements and identify data gaps. In cases of reasonable uncertainty, studies of targeted juvenile should be considered to investigate the safe use levels in food products.

A Guidance Manual for the Toxicity Assessment of Traditional Herbal Medicines

Herbal remedies have been used for thousands of years in worldwide traditional medicines for their potential health benefits. Although they are generally presumed safe unless a significant risk has been identified in humans, increasing number of case reports notify acute or chronic intoxications resulting from their use. This study aims to produce a scientific guide for the evaluation of traditional herbal medicines (THMs) in terms of their toxicity risks based on the published regulatory documents. For this purpose recommended in vitro and in vivo toxicity tests on medicinal products for human use issued by the international regulatory bodies are overviewed and they are then adopted to be used for the toxicity assessment of THMs. Accordingly, based on compilation of these issued regulations, the following tests are recommended for the toxicity assessment of THMs; in vitro cytotoxicity, genotoxicity, acute and repeated dose toxicity, carcinogenicity, reproductive and developmental toxicity, local tolerance tests, toxicokinetic studies, and additional toxicity tests including safety pharmacology, immunotoxicity and antigenicity, endocrine system toxicity, gastro-intestinal toxicity, renal and hepatotoxicity, and drug interaction studies. This study describes and discusses the applicability of these tests for the risk assessment in THMs.

Risk ranking priority of carcinogenic and/or genotoxic environmental contaminants in food in Belgium

This paper focuses on the risks of environmental carcinogenic and/or genotoxic contaminants in food. It describes, for each contaminant studied, the carcinogenicity and genotoxicity, the toxicological reference values, the exposure and the risk characterisation. The compounds studied were classified into 3 categories based on a risk assessment. Effects others than carcinogenicity and/or genotoxicity (e.g. endocrine disruption activity) were also taken into account for the classification. Given the low margin of exposure values for arsenic and lead, these two compounds are classified as priority 1 (high concern) for food safety and as a first priority to take actions to reduce exposure. Cadmium, methylmercury, dioxins and dioxin-like polychlorinated biphenyls (PCB), non-dioxin-like PCB and toxaphene are classified as priority 2 (medium concern). Polybrominated biphenyls, chlordane, heptachlor, dichlorodiphenyltrichloroethane (DDT) and metabolites, hexachlorobenzene, hexachlorocyclohexane (lindane included), polychlorophenols and their salts are classified as priority 3 (low concern).

Critical consideration of the multiplicity of experimental and organismic determinants of pyrethroid neurotoxicity: a proof of concept

Pyrethroids (PYR) are pesticides with high insecticidal activity that may disrupt neuronal excitability in target and nontarget species. The accumulated evidence consistently showed that this neurophysiologic action is followed by alterations in motor, sensorimotor, neuromuscular, and thermoregulatory responses. Nevertheless, there are some equivocal results regarding the potency of PYR in lab animals. The estimation of potency is an important step in pesticide chemical risk assessment. In order to identify the variables influencing neurobehavioral findings across PYR studies, evidence on experimental and organismic determinants of acute PYR-induced neurotoxicity was reviewed in rodents. A comprehensive analysis of these studies was conducted focusing on test material and dosing conditions, testing conditions, animal models, and other determinants such as testing room temperature. Variations in the severity of the neurotoxicity, under lab-controlled conditions, was explained based upon factors including influence of animal species and age, test material features such as chemical structure and stereochemistry, and dosing conditions such as vehicle, route of exposure, and dose volume. If not controlled, the interplay of these factors may lead to large variance in potency estimation. This review examined the scope of acute toxicological data required to determine the safety of pesticide products, and factors and covariates that need to be controlled in order to ensure that predictivity and precaution are balanced in a risk assessment process within a reasonable time-frame, using acute PYR-induced neurotoxicity in rodents as an exemplar.

Critical appraisal of the assessment of benefits and risks for foods, 'BRAFO Consensus Working Group'

BRAFO, Benefit-Risk Analysis for Foods, was a European Commission project funded within Framework Six as a Specific Support Action and coordinated by ILSI Europe. BRAFO developed a tiered methodology for assessing the benefits and risks of foods and food components, utilising a quantitative, common scale for health assessment in higher tiers. This manuscript reports on the implications of the experience gained during the development of the project for the further improvement of benefit-risk assessment methodology. It was concluded that the methodology proposed is applicable to a range of situations and that it does help in optimising resource utilisation through early identification of those benefit-risk questions where benefit clearly outweighs risk or vice versa. However, higher tier assessments are complex and demanding of time and resources, emphasising the need for prioritisation. Areas identified as requiring further development to improve the utility of benefit-risk assessment include health weights for different populations and endpoints where they do not currently exist, extrapolation of effects from studies in animals to humans, use of in vitro data in benefit-risk assessments, and biomarkers of early effect and how these would be used in a quantitative assessment.

Embryo and fetal toxicity of Mentha x villosa essential oil in Wistar rats

CONTEXT

Mentha x villosa Hudson (Lamiaceae) is an aromatic herb employed as a food spice. In folk medicine, it leaves are used as a tranquilizer and anti-hypertensive, even by pregnant women.

OBJECTIVE

There are no reports about its effects in gestation and exposed fetuses, the aim of this study.

MATERIALS AND METHODS

At gestation day (GD) 01, 24 rats were divided in four groups: one control and three experimental groups (n = 6/group). The experimental groups received, by gavage, from GD06 to GD16, 10, 25 or 50 µg/kg/day of Mentha x villosa essential oil. The control group received the vehicle (Tween 80 and distilled water--2%). The parameters of body weight gain, water and food intake were recorded. At GD20 the females were euthanized. Half of the fetuses from each litter were directed for the study of visceral malformations and the remaining fetuses for the study of skeletal malformations.

RESULTS

The statistical analyses revealed absence of alterations in body weight gain, water and food intake, litter weight, fetuses number and weight, reabsorptions and implantations. The treatment revealed absence of visceral and skeletal malformations. The visceral analysis revealed mild hemorrhagic points at brain, but more numerous at kidney, liver and blood vessels near heart, in some fetuses from some experimental litters.

CONCLUSION

The essential oil was not able to promote impairment to the pregnant rats and to gestation. Even occurring lack of malformations, fetotoxicity was revealed by mild hemorrhagic points at liver, kidney, brain and blood vessels of some exposed fetuses.

Review of current and "omics" methods for assessing the toxicity (genotoxicity, teratogenicity and nephrotoxicity) of herbal medicines and mushrooms

ETHNOPHARMACOLOGICAL RELEVANCE

The increasing use of traditional herbal medicines around the world requires more scientific evidence for their putative harmlessness. To this end, a plethora of methods exist, more or less satisfying. In this post-genome era, recent reviews are however scarce, not only on the use of new "omics" methods (transcriptomics, proteomics, metabonomics) for genotoxicity, teratogenicity, and nephrotoxicity assessment, but also on conventional ones.

METHODS

The present work aims (i) to review conventional methods used to assess genotoxicity, teratogenicity and nephrotoxicity of medicinal plants and mushrooms; (ii) to report recent progress in the use of "omics" technologies in this field; (iii) to underline advantages and limitations of promising methods; and lastly (iv) to suggest ways whereby the genotoxicity, teratogenicity, and nephrotoxicity assessment of traditional herbal medicines could be more predictive.

RESULTS

Literature and safety reports show that structural alerts, in silico and classical in vitro and in vivo predictive methods are often used. The current trend to develop "omics" technologies to assess genotoxicity, teratogenicity and nephrotoxicity is promising but most often relies on methods that are still not standardized and validated.

CONCLUSION

Hence, it is critical that toxicologists in industry, regulatory agencies and academic institutions develop a consensus, based on rigorous methods, about the reliability and interpretation of endpoints. It will also be important to regulate the integration of conventional methods for toxicity assessments with new "omics" technologies.

State of the art in benefit-risk analysis: food and nutrition

Benefit-risk assessment in food and nutrition is relatively new. It weighs the beneficial and adverse effects that a food (component) may have, in order to facilitate more informed management decisions regarding public health issues. It is rooted in the recognition that good food and nutrition can improve health and that some risk may be acceptable if benefit is expected to outweigh it. This paper presents an overview of current concepts and practices in benefit-risk analysis for food and nutrition. It aims to facilitate scientists and policy makers in performing, interpreting and evaluating benefit-risk assessments. Historically, the assessments of risks and benefits have been separate processes. Risk assessment is mainly addressed by toxicology, as demanded by regulation. It traditionally assumes that a maximum safe dose can be determined from experimental studies (usually in animals) and that applying appropriate uncertainty factors then defines the 'safe' intake for human populations. There is a minor role for other research traditions in risk assessment, such as epidemiology, which quantifies associations between determinants and health effects in humans. These effects can be both adverse and beneficial. Benefit assessment is newly developing in regulatory terms, but has been the subject of research for a long time within nutrition and epidemiology. The exact scope is yet to be defined. Reductions in risk can be termed benefits, but also states rising above 'the average health' are explored as benefits. In nutrition, current interest is in 'optimal' intake; from a population perspective, but also from a more individualised perspective. In current approaches to combine benefit and risk assessment, benefit assessment mirrors the traditional risk assessment paradigm of hazard identification, hazard characterization, exposure assessment and risk characterization. Benefit-risk comparison can be qualitative and quantitative. In a quantitative comparison, benefits and risks are expressed in a common currency, for which the input may be deterministic or (increasingly more) probabilistic. A tiered approach is advocated, as this allows for transparency, an early stop in the analysis and interim interaction with the decision-maker. A general problem in the disciplines underlying benefit-risk assessment is that good dose-response data, i.e. at relevant intake levels and suitable for the target population, are scarce. It is concluded that, provided it is clearly explained, benefit-risk assessment is a valuable approach to systematically show current knowledge and its gaps and to transparently provide the best possible science-based answer to complicated questions with a large potential impact on public health.

Safety of botanical ingredients in personal care products/cosmetics

The key issue of the safety assessment of botanical ingredients in personal care products (PCP) is the phytochemical characterisation of the plant source, data on contamination, adulteration and hazardous residues. The comparative approach used in the safety assessment of GM-plants may be applied to novel botanical PCP ingredients. Comparator(s) are the parent plant or varieties of the same species. Chemical grouping includes definition of chemical groups suitable for a read-across approach; it allows the estimation of toxicological endpoints on the basis of data from related substances (congeneric groups) with physical/chemical properties producing similar toxicities. The Threshold of Toxicological Concern (TTC) and Dermal Sensitisation Threshold (DST) are tools for the assessment of trace substances or minor ingredients. The evaluation of skin penetration of substances present in human food is unnecessary, whereas mixtures may be assessed on the basis of physical/chemical properties of individual substances. Adverse dermal effects of botanicals include irritation, sensitisation, phototoxicity and immediate-type allergy. The experience from dietary supplements or herbal medicines showed that being natural is not equivalent to being safe. Pragmatic approaches for quality and safety standards of botanical ingredients are needed; consumer safety should be the first objective of conventional and botanical PCP ingredients.

Comparing in vivo, in vitro and in silico methods and integrated strategies for chemical assessment: problems and prospects

The RAINBOW workshop addressed the background for the integration of in vivo, in vitro and computer-based (in silico) methods, to facilitate the study of the toxic properties of chemicals. On the basis of these discussions, we prepared the present paper, outlining the strengths, weaknesses, opportunities and threats of each approach, both alone and integrated into a single testing strategy. The current scheme for evaluation of chemicals needs to be reshaped, in the face of the much larger numbers of chemicals which need to be examined and the availability of a diversified set of tools.

Safety assessment of personal care products/cosmetics and their ingredients

We attempt to review the safety assessment of personal care products (PCP) and ingredients that are representative and pose complex safety issues. PCP are generally applied to human skin and mainly produce local exposure, although skin penetration or use in the oral cavity, on the face, lips, eyes and mucosa may also produce human systemic exposure. In the EU, US and Japan, the safety of PCP is regulated under cosmetic and/or drug regulations. Oxidative hair dyes contain arylamines, the most chemically reactive ingredients of PCP. Although arylamines have an allergic potential, taking into account the high number of consumers exposed, the incidence and prevalence of hair dye allergy appears to be low and stable. A recent (2001) epidemiology study suggested an association of oxidative hair dye use and increased bladder cancer risk in consumers, although this was not confirmed by subsequent or previous epidemiologic investigations. The results of genetic toxicity, carcinogenicity and reproductive toxicity studies suggest that modern hair dyes and their ingredients pose no genotoxic, carcinogenic or reproductive risk. Recent reports suggest that arylamines contained in oxidative hair dyes are N-acetylated in human or mammalian skin resulting in systemic exposure to traces of detoxified, i.e. non-genotoxic, metabolites, whereas human hepatocytes were unable to transform hair dye arylamines to potentially carcinogenic metabolites. An expert panel of the International Agency on Research of Cancer (IARC) concluded that there is no evidence for a causal association of hair dye exposure with an elevated cancer risk in consumers. Ultraviolet filters have important benefits by protecting the consumer against adverse effects of UV radiation; these substances undergo a stringent safety evaluation under current international regulations prior to their marketing. Concerns were also raised about the safety of solid nanoparticles in PCP, mainly TiO(2) and ZnO in sunscreens. However, current evidence suggests that these particles are non-toxic, do not penetrate into or through normal or compromised human skin and, therefore, pose no risk to human health. The increasing use of natural plant ingredients in personal care products raised new safety issues that require novel approaches to their safety evaluation similar to those of plant-derived food ingredients. For example, the Threshold of Toxicological Concern (TTC) is a promising tool to assess the safety of substances present at trace levels as well as minor ingredients of plant-derived substances. The potential human systemic exposure to PCP ingredients is increasingly estimated on the basis of in vitro skin penetration data. However, new evidence suggests that the in vitro test may overestimate human systemic exposure to PCP ingredients due to the absence of metabolism in cadaver skin or misclassification of skin residues that, in vivo, remain in the stratum corneum or hair follicle openings, i.e. outside the living skin. Overall, today's safety assessment of PCP and their ingredients is not only based on science, but also on their respective regulatory status as well as other issues, such as the ethics of animal testing. Nevertheless, the record shows that today's PCP are safe and offer multiple benefits to quality of life and health of the consumer. In the interest of all stakeholders, consumers, regulatory bodies and producers, there is an urgent need for an international harmonization on the status and safety requirements of these products and their ingredients.

High dose selection in general toxicity studies for drug development: A pharmaceutical industry perspective

The choice of an appropriate high dose for nonclinical toxicology studies continues to generate significant discussion and debate. Typically, use of the term "high dose" reflects a consideration of a Maximum Tolerated Dose (MTD) or a Maximum Feasible Dose (MFD), inexact terms applied to the design of nonclinical studies conducted to support human clinical trials for experimental new drugs. A pharmaceutical industry perspective on appropriate considerations for high doses in nonclinical studies is provided herein, however, the basic principles applied to the design of toxicology studies translate across the areas of Regulatory, Academic, and Industrial toxicology. Dose selection approaches for nonclinical studies of safety assessment for pharmaceuticals should consider the need to demonstrate the full range of the dose-response continuum (e.g., NOAEL through a toxic dose), however, should also take into account relevance to human therapeutic doses and incorporate clinical indication- and phase-specific considerations.

Toxicological profiling of chemical and environmental samples using panels of test organisms and optical oxygen respirometry

A simple and versatile methodology for high throughput toxicological assessment of chemical and environmental samples is presented. It uses panels of test organisms ranging from prokaryotic (E. coli, V. fischeri) and eukaryotic (Jurkat) cells to invertebrate (Artemia salina) and vertebrate (Danio rerio) organisms, to analyze alterations in their oxygen consumption by optical oxygen respirometry. All the assays are carried out in a convenient microtiter plate format using commercial reagents (phosphorescent oxygen probe, microplates) and detection on a standard fluorescent plate reader. Simple experimental set-up and mix-and-measure procedure allow parallel assessment of up to 96 samples (or assay points) in 2 h, easy generation of dose- and time-dependent responses, and EC(50) values. The methodology was demonstrated with several different classes of chemicals including heavy metal ions, PAHs, pesticides, their mixtures, and also validated with complex environmental samples such as wastewater from a wastewater treatment plant. It has been shown to provide high sensitivity, sample throughput and information content, flexibility and general robustness. It allows ranking and profiling of samples, compares favorably with alternative methods such as MicroTox and mortality tests with animal models, and is well suited for large-scale monitoring programs such as CWA and WFD.

Is a quantitative risk assessment of air quality in underground parking garages possible?

Little information is available about the health risks associated with time spent in underground parking garages. The objective of this study was to determine whether it is possible to quantify the health risks associated with these garages without epidemiologic data on the subject. We followed the standard procedure for health risk assessment. We searched the literature for pollutant concentrations in the air samples of underground parking garages, the hazards associated with their inhalation, and their toxicological reference values. Conditions of occupational and user exposure were estimated by scenarios and taken into account to discuss toxicological reference values by modifying (with Haber's law) the adjustment factors for exposure frequency and duration. Risk quantification was possible for 39 pollutants. Acute exposures to CO and NO2 exceed toxicological reference values, as does chronic exposure to benzene for threshold effects. The risk of a carcinogenic effect associated with benzene may be greater than 10(-5). Excess exposure to air pollution indicators (PM and NO2) is also elevated, judging by the WHO Air Quality Guidelines, and also when comparing to levels with reported effects in epidemiologic studies. The risk associated with underground parking garages can be evaluated only in part. The information available is nonetheless sufficient to justify actions to reduce exposure.

PRACTICAL IMPLICATIONS

The risks associated with exposure in underground parking garages cannot be thoroughly evaluated because of inadequate knowledge of exposures and of the toxicity of pollutants. The available knowledge is nonetheless sufficient to advise that risk management measures should be taken to reduce both acute and chronic exposures.

On the incorporation of chemical-specific information in risk assessment

This paper describes the evolution of chemical risk assessment from its early dependence on generic default approaches to the current situation in which mechanistic and biokinetic data are routinely incorporated to support a more chemical-specific approach. Two methodologies that have played an important role in this evolution are described: mode-of-action evaluation and physiologically based biokinetic (PBBK) modelling. When used together, these techniques greatly increase the opportunity for the incorporation of biokinetic and mechanistic data in risk assessment. The resulting risk assessment approaches are more appropriately tailored to the specific chemical and are more likely to provide an accurate assessment of the potential hazards associated with human exposures. The appropriate application of PBBK models in risk assessment demands well-formulated statements about the chemical mode of action. It is this requirement for an explicit, mechanistic hypothesis that gives biologically motivated models their power, but at the same time serves as the greatest impediment to the acceptance of a chemical-specific risk assessment approach by regulators. The chief impediment to the regulatory acceptance and application of PBBK models in risk assessment is concern about uncertainties associated with their use. To some extent such concerns can be addressed by the development of generally accepted approaches for model evaluation and quantitative uncertainty analysis. In order to assure the protection of public health while limiting the economic and social consequences of over-regulation, greater dialogue between researchers and regulators is crucially needed to foster an increased use of emerging scientific information and innovative methods in chemical risk assessments.

Safety assessment of food products from r-DNA animals

Recombinant-DNA (transgenic) animals intended for food production are approaching the market. Among them, recombinant-DNA fishes constitute the most advanced case. As a result, intergovernmental organizations are working on guidelines which would eventually become international standards for national food safety assessments of these products. This article reviews the emerging elements for the food safety assessment of products derived from recombinant-DNA animals. These elements will become highly relevant both for researchers and regulators interested in developing or analyzing recombinant-DNA animals intended to be used in the commercial elaboration of food products. It also provides references to science-based tools that can be used to support food safety assessments. Finally, it proposes recommendations for the further development of biosafety assessment methodologies in this area.

Cassava starch fermentation wastewater: Characterization and preliminary toxicological studies

Cassava starch fermentation wastewater is an industrial residue composed mainly of lactic acid bacteria with predominance of the genera Lactobacillus, and organic acids. To evaluate the safety of this residue for possible production of probiotic beverages, acute in mice and sub-chronic (28-day repeated dose) toxicity studies in rats were carried. The administration of a single dose of 5 g/kg/body weight did not produce mortality in mice. Rats treated with water containing 0 (control), 25%, 50%, and 100% of the residue for 28 days, did not present alterations in behaviour or in food and water consumption. There were no treatment-related changes of toxicological significance in the relative weight of the organs neither in the haematological nor in the biochemical parameters. Histopathologic alterations observed in the small intestine did not seem to be associated with the treatment.

Human variability in hepatic and renal elimination: implications for risk assessment

Hepatic metabolism and renal excretion constitute the main routes of xenobiotic elimination in humans. Improving human risk assessment for threshold contaminants requires the incorporation of quantitative data related to their elimination (toxicokinetics) and potential toxic effects (toxicodynamics). This type of data provides a scientific basis to replace the standard uncertainty factor (UF = 10) allowing for the consideration of human variability in toxicokinetics and toxicodynamics. This review focuses on recent research efforts aiming to incorporate human variability in hepatic and renal elimination (toxicokinetics) into the risk assessment process. A therapeutic drug database was developed to quantify pathway-related variability in human phase I and phase II hepatic metabolism as well as renal excretion in subgroups of the population (healthy adults, neonates and the elderly), using data on compounds cleared primarily through each route (> 60% dose). For each subgroup of the population and elimination route, pathway-related UFs were then derived to cover 95-99% of each subgroup. Overall, the default toxicokinetic UFs would not cover neonates, the elderly for most elimination routes and any subgroup of the population for compounds metabolized via polymorphic isozymes (such as CYP2C19 and CYP2D6). These pathway-related UFs allow the incorporation of in vivo metabolism and toxicokinetic data in the risk assessment process and provide a flexible intermediate option between the default UF and chemical-specific adjustment factors (CSAFs) derived from physiologically based pharmacokinetic models. Implications of human variability in hepatic metabolism and renal excretion for chemical risk assessment are discussed.

Approaches to the risk assessment of genotoxic carcinogens in food: A critical appraisal

The present paper examines the particular difficulties presented by low levels of food-borne DNA-reactive genotoxic carcinogens, some of which may be difficult to eliminate completely from the diet, and proposes a structured approach for the evaluation of such compounds. While the ALARA approach is widely applicable to all substances in food that are both carcinogenic and genotoxic, it does not take carcinogenic potency into account and, therefore, does not permit prioritisation based on potential risk or concern. In the absence of carcinogenicity dose-response data, an assessment based on comparison with an appropriate threshold of toxicological concern may be possible. When carcinogenicity data from animal bioassays are available, a useful analysis is achieved by the calculation of margins of exposure (MOEs), which can be used to compare animal potency data with human exposure scenarios. Two reference points on the dose-response relationship that can be used for MOE calculation were examined; the T25 value, which is derived from linear extrapolation, and the BMDL10, which is derived from mathematical modelling of the dose-response data. The above approaches were applied to selected food-borne genotoxic carcinogens. The proposed approach is applicable to all substances in food that are DNA-reactive genotoxic carcinogens and enables the formulation of appropriate semi-quantitative advice to risk managers.

Understanding and applying regulatory guidance on the nonclinical development of biotechnology-derived pharmaceuticals

Biotechnology-derived pharmaceuticals are a well established and growing part of the therapeutic armamentarium. Beginning with recombinant versions of products such as insulin that were previously manufactured by extraction from animal and human sources, licensed biotechnology drugs and those in development now span an ever-increasing range of product types and therapeutic categories. As a consequence of this diversity, both general and product class-specific scientific guidelines have been developed on a regional (e.g. EU/US) or international (e.g. ICH - International Conference on Harmonization) basis. The current portfolio of nonclinical guidelines, particularly ICH S6, emphasizes flexibility and adaptability to the specific circumstances of the individual biotechnology product and its intended indication, taking into account factors not generally applicable to small-molecule drugs, such as pharmacodynamic responsiveness of safety and efficacy models, species specificity, and antibody formation. Guidelines developed principally with small-molecule drugs in mind may, nevertheless, have some applicability to biotechnology drugs on issues such as safety pharmacology, as well as on regulatory, procedural and dossier submission requirements. Scientific guidelines, such as those providing nonclinical guidance, are just one, albeit important, component of an increasingly complex legal/scientific environment in drug development.

Risk Assessment of Endocrine Disrupters: The Role of Toxicological Studies

Endocrine disrupters (ED) represent a good challenge for experimental toxicology. In order to deal with several critical points relevant to risk assessment: (a) ED may induce long-term effects upon exposure in susceptible developmental phases, including postnatal life up to puberty; thus, efforts are required to refine testing strategies, for example, by supporting the two-generation rodent study with a comprehensive in vitro/in vivo screening battery; (b) due to the regulatory role of endocrine homeostasis, mechanisms of endocrine disruption may impact on immune, neurobehavioral, and reproductive development, as well as on susceptibility to cancer; (c) the potential multiple exposure to ED with common targets through diet and/or living environment calls for the development of models to understand mechanisms of interactions and effects of mixtures; and (d) last but not least, ED may interact with a number of factors related to differential vulnerability of individuals or population subgroups, including the intake of nutrients or bioactive food components. Besides reducing the chance for noxious chemicals to enter our life, toxicological research on mechanisms may also lead to the definition of possible biomarkers of exposure, effect, and susceptibility that may be further exploited in human health surveillance.

Statistical evaluation of chronic toxicity data on aquatic organisms for the hazard identification: the chemicals toxicity distribution approach

Presently, in the Globally Harmonised System of Classification and Labelling of Chemicals the classification of substances for long-term effects to aquatic life is based on acute toxicity in combination with degradation and/or bioaccumulation potential. Recently an OECD Working Group was created to develop the classification scheme to accommodate chronic toxicity data related to aquatic organisms for assigning a chronic hazard category. This study focuses on a new approach for setting chronic toxicity cut-off values based on Chemicals Toxicity Distributions (CTDs). A CTD is obtained through statistical fitting of the data used by regulatory bodies for setting hazard-based classifications. The CTDs were made using the lowest aquatic NOEC value of each chemical. A review of different toxicological sources reporting acute aquatic toxicities was carried out. Initially, the data were arranged according to the specific source and distributions for key taxonomic groups (i.e. fishes, crustaceans and algae) were evaluated separately. In most cases, no significant departures from normality were observed. Thereafter, a compiled database containing >900 values was developed and the CTDs were constructed for each taxonomic group. Significant deviation from normality (P < 0.05) was observed in the fishes and crustaceans' CTDs. However, this deviation was apparently produced by the presence of only seven values with NOECs <1 x 10(-5) mg l(-1), while high correlation between the data and the normal scores (r-values>or= 0.989) indicated that the data were samples from normal distributions. From these observations, potential cut-off values would allow quantitative estimations of the percentage of chemicals falling into each specific category. This approach results in a simple classification hazard scheme where most chemicals are covered in one of the categories, allowing a clear distribution of the chemicals among three categories for chronic toxicity.

An overview of evidence for a causal relationship between dietary availability of choline during development and cognitive function in offspring

This review is part of a series intended for non-specialists that will provide an overview of evidence for causal relationships between micronutrient deficiencies and brain function. Here, we review 34 studies in rodents linking the availability of choline during gestation and perinatal development to neurological function or performance of offspring in cognitive and behavioral tests. Experimental designs, major results, and statistical criteria are summarized in Tables 1-4. Based on our reading of the literature, the evidence suggests that choline supplementation during development results in improved performance of offspring in cognitive or behavioral tests, and in changes in a variety of neurological functional indicators: (1) enhanced performance was observed, particularly on more difficult tasks; (2) increases (choline supplementation) or decreases (choline deficiency) were observed in electrophysiological responsiveness and size of neurons in offspring; and (3) supplementation resulted in some protection against adverse effects of several neurotoxic agents (including alcohol) in offspring. Discussion topics include methodological issues, such as the importance of independent replication, causal criteria, and uncertainties in interpreting test results.

Risk assessment of chemicals potentially affecting male fertility

Male reproductive toxicity involves a broad range of targets and mechanisms such as direct effects on the seminiferous epithelium and/or on Leydig and Sertoli cells supporting spermatogenesis, epididymal sperm maturation as well as endocrine disruption. Direct effects on spermatogenesis may be adequately revealed through both reproduction and repeated-dose toxicity studies; however, more research is needed on early markers of effect and on long-term sequelae of short-term exposures. Endocrine-related mechanisms are particularly relevant to subtle, but persistent effects on reproductive development due to altered early programming; the two-generation study is the test of choice, whereas targeted studies on the prepubertal phase are also desirable. Studies using in vitro methods as well as toxicogenomics are increasing; although gaps exist and much validation work is needed, in perspective, such approaches may be important in order to select compound, understand mechanisms, as well identify biomarkers of potential use also in human studies.

The refinement of uncertainty/safety factors in risk assessment by the incorporation of data on toxicokinetic variability in humans

The derivation of safe levels of exposure in humans for compounds that are assumed to cause threshold toxicity has relied on the application of a 100-fold uncertainty factor to a measure for the threshold, such as the no observed adverse effect level (NOAEL) or the benchmark dose (BMD). This 100-fold safety factor consists of the product of two 10-fold factors allowing for human variability and interspecies differences. The International Programme on Chemical Safety has suggested the subdivision of these 10-fold factors to allow for variability in toxicokinetics and toxicodynamics. This subdivision allows the replacement of the default uncertainty factors with a chemical-specific adjustment factor (CSAF) when suitable data are available. This short review describes potential options to refine safety factors used in risk assessment, with particular emphasis on pathway-related uncertainty factors associated with variability in kinetics. These pathway-related factors were derived from a database that quantified interspecies differences and human variability in phase I metabolism, phase II metabolism, and renal excretion. This approach allows metabolism and pharmacokinetic data in healthy adults and subgroups of the population to be incorporated in the risk-assessment process and constitutes an intermediate approach between simple default factors and chemical-specific adjustment factors.

Human exposure and internal dose assessments of acrylamide in food

This review provides a framework contributing to the risk assessment of acrylamide in food. It is based on the outcome of the ILSI Europe FOSIE process, a risk assessment framework for chemicals in foods and adds to the overall framework by focusing especially on exposure assessment and internal dose assessment of acrylamide in food. Since the finding that acrylamide is formed in food during heat processing and preparation of food, much effort has been (and still is being) put into understanding its mechanism of formation, on developing analytical methods and determination of levels in food, and on evaluation of its toxicity and potential toxicity and potential human health consequences. Although several exposure estimations have been proposed, a systematic review of key information relevant to exposure assessment is currently lacking. The European and North American branches of the International Life Sciences Institute, ILSI, discussed critical aspects of exposure assessment, parameters influencing the outcome of exposure assessment and summarised data relevant to the acrylamide exposure assessment to aid the risk characterisation process. This paper reviews the data on acrylamide levels in food including its formation and analytical methods, the determination of human consumption patterns, dietary intake of the general population, estimation of maximum intake levels and identification of groups of potentially high intakes. Possible options and consequences of mitigation efforts to reduce exposure are discussed. Furthermore the association of intake levels with biomarkers of exposure and internal dose, considering aspects of bioavailability, is reviewed, and a physiologically-based toxicokinetic (PBTK) model is described that provides a good description of the kinetics of acrylamide in the rat. Each of the sections concludes with a summary of remaining gaps and uncertainties.

Risk-benefit analysis of micronutrients

Traditionally, different approaches have been used to determine the recommended dietary allowances for micronutrients, above which there is a low risk of deficiency, and safe upper levels, below which there is a negligible risk of toxicity. The advice given to risk managers has been in the form of point estimates, such as the recommended dietary allowance (RDA) and the tolerable upper level (UL). In future, the gap between the two intake-response curves may become narrower, as more sensitive indicators of deficiency and toxicity are used, and as health benefits above the recommended daily allowance are taken into account. This paper reviews the traditional approaches and proposes a novel approach to compare beneficial and adverse effects across intake levels. This model can provide advice for risk managers in a form that will allow the risk of deficiency or the risk of not experiencing the benefit to be weighed against the risk of toxicity. The model extends the approach used to estimate recommended dietary allowances to make it applicable to both beneficial and adverse effects and to extend the intake-incidence data to provide a range of estimates that can be considered by the risk manager. The data-requirements of the model are the incidence of a response at one or more levels of intake, and a suitable coefficient of variation to represent the person-to-person variations within the human population. A coefficient of variation of 10% or 15% has been used for established recommended dietary allowances and a value of 15% is proposed as default for considerations of benefit. A coefficient of variation of 45% is proposed as default for considerations of toxicity, based on analyses of human variability in the fate and effects of therapeutic drugs. Using this approach risk managers, working closely with risk assessors, will be able to define ranges of intake based on a balance between the risks of deficiency (or lack of benefit) and toxicity.