Toxicological Risk Assessment Research Articles

Sorption and dissolution of bare and coated silver nanoparticles in soil suspensions—Influence of soil and particle characteristics

The increasing use of silver nanoparticles (AgNPs) in consumer products triggers the need for investigations that improve the understanding of their chemical transformations upon environmental entry. Such knowledge provides crucial information for toxicological studies and risk assessments. Interactions with the soil compartment need to be explored as there are evident risks of the dispersion of both AgNPs and of released Ag ions/complexes present in wastewater-treated sludge that is distributed onto agricultural land. The dissolution and fractionation in solution of bare (AgNP-bare, noncoated) and coated AgNPs (AgNP-coat, stabilized with two nonionic surfactants, polyoxyethylene glycerol trioleate and Tween 20) were investigated after 4 and 48 h in suspensions of one sandy and one clayey soil of different pHs (3.3, 5.2). Parallel experiments were performed with soil suspensions spiked with easily soluble AgNO3. Silver in the water phase was separated in a dissolved fraction (mainly Ag ions/complexes) and a particle fraction (mainly AgNP/agglomerates/Ag adsorbed on organic matter) by means of ultracentrifugation. Bare AgNPs were nonstable and dissolved to a significantly larger extent in the sandy soil mixture compared to coated AgNPs. The concentration of dissolved Ag (ions/complexes) in the water phase was similar in the case of bare AgNPs and AgNO3 (at pH 3 and 5.2) after 24 h in sandy soil, which implies a high degree of dissolution of bare AgNPs (50–100%). In contrast, approximately 50% of the coated AgNPs remained in the water phase after 48 h of equilibration in the sandy soil at pH 5.2. The clayey soil had a significantly higher sorption capacity of Ag compared with the sandy soil, as Ag in the case of coated AgNPs was only detected in the water phase of pH 5.2 (<1 % of added Ag). Ultracentrifugation was proven more efficient compared with microfiltration to separate the dissolved Ag fraction (ions/complexes) and the particle fraction (AgNPs/agglomerates) of the water phase. This fractionation is not a measure of any potential toxicity.

Chemical Synonyms, Molecular Structure and Toxicological Risk Assessment of Synthetic Textile Dyes: A Critical Review

Textile industry has been considered for years to be one of the major sources of worldwide pollution problems. Huge amount of wastewater is generated at different stages of textile manufacturing. These waste products are mostly released in the environment without prior consideration. In Fact, they are highly contaminated with lot of chemicals including dyes. For this reason, the investigation of the effects of those compounds over the environment and human health has become a great interest. This review outlines the chemical synonyms, molecular structure and the toxicological effects of 85 textile dyes. The potential fate and effect of those substances on aquatic, human health and ecosystem are discussed in this article.

Concentrations of phthalates in bottled water under common storage conditions: Do they pose a health risk to children?

Of recent concern is the migration of phthalates from plastic products such as Polyethylene Terephthalate (PET) bottles into the water contain. These concerns should be addressed, especially considering the steady growth of the consumption of bottled water and the toxicological effects of phthalates. In this regard, special attention should be paid to children's consumption because of their particular susceptibility to the effects of phthalates.The aim of this study was to determine the concentrations of phthalates, including dibutyl phthalate (DBP), butyl benzyl phthalate (BBP) and bis(2-ethylhexyl) phthalate (DEHP), in bottled water and to estimate the health risk of endocrine disrupting chemicals due to water intake in children for the first time.Migration of phthalates was investigated in PET-bottled water under various storage conditions using gas chromatography–mass spectroscopy. A phthalate exposure assessment was performed to characterize their risk to the children's health via a calculated hazard quotient (HQ).It seems that increase in the temperature and the duration of storage affect phthalate migration, but the level of DEHP in bottled water was always very low and does not exceed 26.83% of the U.S. EPA maximum concentration limit (MCL). In particular, phthalate migration was not substantial at low temperatures (<25°C) and freezing conditions and the most abundant phthalate (DEHP) was not more than 10.6% MCL.The estimated child intake ranged from 0.01μg/kg/day for BBP to 0.24μg/kg/day for DEHP. Estimated phthalate intakes are generally in the safe range and exposure decreased with increasing age. Toxicological risk assessment of the maximum concentrations measured revealed a maximum HQ of 0.012 in the worst condition. Furthermore, a negligible carcinogenic risk of 6.5×10−7 for DEHP was observed. Consequently, risk evaluation showed that bottled water is safe for consumption by children.

Spectroscopic and chromatographic quantification of an antioxidant-stabilized ultrahigh-molecular-weight polyethylene.

The oxidative stability of various antioxidant-containing ultrahigh-molecular-weight polyethylene (UHMWPE) formulations has been widely reported. Depending on which specific antioxidant is used, the process by which it is incorporated into UHMWPE, and the amount of the antioxidant incorporated, there could be substantial differences in the material and toxicological properties of the UHMWPE formulation. Pentaerythritol tetrakis (3-[3,5-di tertiary butyl-4-hydroxyphenyl] propionate) (PBHP) has been extensively used as an efficient antioxidant in various applications. However, it has not thus far been used to stabilize UHMWPE in orthopaedic implants. It is therefore important to characterize and verify the concentration and homogeneity of distribution of PBHP in the composition, the chemical consequence of exposure of the antioxidant to gamma irradiation, and to assess the toxicological risk of use by the identification and quantification of leachables before the use of PBHP-containing UHMWPE in implantable devices. (1) Can the concentration and uniformity of distribution of the antioxidant PBHP in UHMWPE powder and in the consolidated, preirradiated formulation be verified? (2) Can the leachable compounds in the gamma radiation crosslinked PBHP/UHMWPE formulation be identified and quantified? PBHP in GUR 1020 UHMWPE was quantified by Fourier transform infrared (FTIR) and ultraviolet-visible (UV-Vis) spectroscopy. The chemical byproducts generated by gamma irradiation of PBHP were identified using gas chromatography in conjunction with mass spectrometry followed by a second-stage mass spectrometry (GC-MS/MS). When GC-MS/MS was coupled with Stir Bar Sorptive extraction, leachable components in the UHMWPE formulation were identified and quantified. The percent concentration of PBHP in UHMWPE powder was confirmed by UV-Vis spectroscopy and the concentration and uniform distribution of PBHP in UHMWPE after consolidation and before radiation crosslinking was verified through FTIR spectroscopy. GC-MS/MS analysis enabled the identification and quantification of 16 gamma irradiation byproducts of PBHP. These 16 compounds were verified as potentially leachable compounds in PBHP-stabilized UHMWPE and were found to be well below the safety threshold concern of 150 ng/device in orthopaedic knee inserts made from PBHP-stabilized UHMWPE. Spectroscopic analysis has been successfully used to demonstrate the ability to reliably quantify the amount as well as the distribution of PBHP in UHMWPE in orthopaedic bearings. State-of-the-art chemical extraction and analytical techniques have enabled the identification of the gamma radiation-induced byproducts of PBHP and the quantification of these components as leachables from the PBHP-stabilized UHMWPE formulation. Antioxidant-stabilized UHMWPE materials being considered for orthopaedic bearings must be fully characterized for composition before use because it is apparent that exposure to high doses of gamma radiation would cause the formation of new chemical entities. It is important to verify the identities and quantities of chemical species that could leach out of implanted devices in the long term to enable their toxicological risk assessment.

Mass poisoning events

Mass poisoning events are rare and different in some respects from other mass casualties, especially with regard to diagnosis and triage. Based on the description of important historical events and experiences of poison control centers, an overview is provided for different types of mass poisoning events as well as guidelines for specific medical management. The review is based on a literature search and case reports notified to the Giftinformationszentrum-Nord Poisons Center. Toxicological risk assessment is based on identification of all relevant agents, evaluation of their toxic hazards (toxicity), and evaluation of the exposure (dose and pathway) for all persons exposed. This risk assessment constitutes the basis of medical diagnosis and management. In cases of suspicion of poisoning or poisonings caused by illegal drugs, risk assessment may be difficult due to the lack of important data needed for risk assessment. Mass poisonings caused by ethanol or contaminated food are well understood, with therapy being mainly symptomatic. However, in rare poisonings by other agents, a specific antidote treatment may be important. Thus, adequate antidote supplies must be available for these events. As hardly any medical professional has personal practical knowledge of mass poisoning casualties, such events are unique experiences. Thorough preparation and intensive cooperation with poison control centers and-if applicable-public health authorities may be important for best practice event management.

Characterization of Alternaria strains from Argentinean blueberry, tomato, walnut and wheat

Alternaria species have the ability to produce a variety of secondary metabolite, which plays important roles in food safety. Argentina is the second largest exporter of fresh and processed food products to Europe, however, few studies on Alternaria mycotoxins and other bioactive secondary metabolites have been carried out on Argentinean cereals, fruit and vegetables. Knowing the full chemical potential and the distribution of Alternaria spp. on crops, it is necessary to establish a toxicological risk assessment for food products for human consumption. In the present study, 87 Alternaria strains from different substrates (tomato, wheat, blueberries and walnuts) were characterized according to morphology and metabolite production. Aggressive dereplication (accurate mass, isotopic patterns and lists of all described compounds from Alternaria) was used for high-throughput evaluation of the chemical potential. Four strains belonged to the Alternaria infectoria sp.-grp., 6 to the Alternaria arborescens sp.-grp., 6 showed a sporulation pattern similar to that of “M” according to Simmons, 1 to that of Alternaria vaccinii, and the remaining 70 constituted a diverse group belonging to morphological groups “G” and “H”. The cluster analysis yielded 16 almost identical dendrograms and grouped the Alternaria strains into four clusters and 11 singletons and outlier groups. The chemical analysis showed that AOH and AME were the most common metabolites produced, followed by TEN, ALXs and TeA. The A. infectoria sp.-grp. had no metabolites in common with the rest of the strains. Several secondary metabolites isolated from large-spored Alternaria species or other fungal genera were detected, such as dehydrocurvularin, pyrenochaetic acid and alternarienonic acid. The strains isolated from tomato produced lower amounts of metabolites than strains from blueberries, walnut and wheat, although individual strains from tomato produced the highest amount of some metabolites. The A. infectoria sp.-grp. was unique to cereals, whereas strains classified as belonging to the A. arborescens sp.-grp or having sporulation pattern “M” were only isolated from tomatoes. Otherwise, no clear association between substrate and identity could be found. The analyses in the study show that at least 75% of the Argentinean strains are able to produce potential mycotoxins.

In Vitro Cell Culture Models of Hepatic Steatosis.

The liver is the systemic hub of lipid metabolism. The excessive accumulation of lipids in hepatocytes, steatosis, is a major clinical concern, whose progressive forms lead to end-stage liver disease. Currently, animal studies are the gold standard in toxicological risk assessment. Fueled by an integration of modern omics technologies, in silico models and in vitro system optimization, a new paradigm in the basis for toxicological risk assessment is emerging away from the use of animals. In recent years, in vitro assays have been developed for the early screening of the steatogenic potential of compounds. The present chapter describes an assay for the intracellular detection of lipids, a high-content screen for the distinction between steatosis and phospholipidosis, a multiparametric high-content screen for steatogenic potential and a liver X receptor reporter cell line.

In Vitro Characterization for Human Serum Albumin Binding Sorafenib, A Multi Kinase Inhibitor: Spectroscopic Study

The affinity between sorafenib and human serum albumin (HSA) was investigated by molecular modeling techniques and spectroscopic methods. The results of fluorescence spectroscopy, three-dimensional (3D) fluorescence, Fourier transform infrared (FTIR) and circular dichroism (CD) spectroscopy suggest that sorafenib has a strong ability to quench the intrinsic fluorescence of HSA. The binding affinity (K A) and the number of binding sites (n) between sorafenib and HSA at 305 K were estimated as 2.64 × 104 L·mol−1 and 1, respectively. The apparent distance between the Trp214 and sorafenib is 4.41 nm. Additionally, the binding of sorafenib induced conformational changes of disulfide bridges of HSA with decrease of the α-helix content. The resonance light scattering (RLS) spectra showed that the dimension of the individual HSA molecules are larger after interaction with sorafenib. These studies provide more information on the potential pharmaceutical effects and toxicological risk assessment of sorafenib.

IWGT report on quantitative approaches to genotoxicity risk assessment II. Use of point-of-departure (PoD) metrics in defining acceptable exposure limits and assessing human risk

This is the second of two reports from the International Workshops on Genotoxicity Testing (IWGT) Working Group on Quantitative Approaches to Genetic Toxicology Risk Assessment (the QWG). The first report summarized the discussions and recommendations of the QWG related to the need for quantitative dose–response analysis of genetic toxicology data, the existence and appropriate evaluation of threshold responses, and methods to analyze exposure-response relationships and derive points of departure (PoDs) from which acceptable exposure levels could be determined. This report summarizes the QWG discussions and recommendations regarding appropriate approaches to evaluate exposure-related risks of genotoxic damage, including extrapolation below identified PoDs and across test systems and species. Recommendations include the selection of appropriate genetic endpoints and target tissues, uncertainty factors and extrapolation methods to be considered, the importance and use of information on mode of action, toxicokinetics, metabolism, and exposure biomarkers when using quantitative exposure-response data to determine acceptable exposure levels in human populations or to assess the risk associated with known or anticipated exposures. The empirical relationship between genetic damage (mutation and chromosomal aberration) and cancer in animal models was also examined. It was concluded that there is a general correlation between cancer induction and mutagenic and/or clastogenic damage for agents thought to act via a genotoxic mechanism, but that the correlation is limited due to an inadequate number of cases in which mutation and cancer can be compared at a sufficient number of doses in the same target tissues of the same species and strain exposed under directly comparable routes and experimental protocols.

IWGT report on quantitative approaches to genotoxicity risk assessment I. Methods and metrics for defining exposure–response relationships and points of departure (PoDs)

This report summarizes the discussion, conclusions, and points of consensus of the IWGT Working Group on Quantitative Approaches to Genetic Toxicology Risk Assessment (QWG) based on a meeting in Foz do Iguaçu, Brazil October 31–November 2, 2013. Topics addressed included (1) the need for quantitative dose–response analysis, (2) methods to analyze exposure–response relationships & derive point of departure (PoD) metrics, (3) points of departure (PoD) and mechanistic threshold considerations, (4) approaches to define exposure-related risks, (5) empirical relationships between genetic damage (mutation) and cancer, and (6) extrapolations across test systems and species. This report discusses the first three of these topics and a companion report discusses the latter three. The working group critically examined methods for determining point of departure metrics (PoDs) that could be used to estimate low-dose risk of genetic damage and from which extrapolation to acceptable exposure levels could be made using appropriate mode of action information and uncertainty factors. These included benchmark doses (BMDs) derived from fitting families of exponential models, the No Observed Genotoxic Effect Level (NOGEL), and “threshold” or breakpoint dose (BPD) levels derived from bilinear models when mechanistic data supported this approach. The QWG recognizes that scientific evidence suggests that thresholds below which genotoxic effects do not occur likely exist for both DNA-reactive and DNA-nonreactive substances, but notes that small increments of the spontaneous level cannot be unequivocally excluded either by experimental measurement or by mathematical modeling. Therefore, rather than debating the theoretical possibility of such low-dose effects, emphasis should be placed on determination of PoDs from which acceptable exposure levels can be determined by extrapolation using available mechanistic information and appropriate uncertainty factors. This approach places the focus on minimization of the genotoxic risk, which protects against the risk of the development of diseases resulting from the genetic damage. Based on analysis of the strengths and weaknesses of each method, the QWG concluded that the order of preference of PoD metrics is the statistical lower bound on the BMD>the NOGEL>a statistical lower bound on the BPD. A companion report discusses the use of these metrics in genotoxicity risk assessment, including scaling and uncertainty factors to be considered when extrapolating below the PoD and/or across test systems and to the human.

Towards a strategic approaches in alternative tests for pesticide safety.

Pesticides have provided significant benefits including plant disease control and increased crop yields since people developed and utilized them. However, pesticide use is associated with many adverse effects, which necessitate precise toxicological tests and risk assessment. Most of these methods are based on animal studies, but considerations of animal welfare and ethics require the development of alternative methods for the evaluation of pesticide toxicity. Although the usage of laboratory animals is inevitable in scientific evaluation and alternative approaches have limitations in the whole coverage, continuous effort is necessary to minimize animal use and to develop reliable alternative tests for pesticide evaluation. This review discusses alternative approaches for pesticide toxicity tests and hazard evaluation that have been used in peer-reviewed reports and could be applied in future studies based on the critical animal research principles of reduction, replacement, and refinement.

Forensic issues in the analysis of trace nitrofuran veterinary residues in food of animal origin

Over the past twelve years hundreds of official analyses for nitrofuran antibiotic residues in farmed shrimp and prawns have led to product recalls, border rejections, and de-listed suppliers. Positive-release testing regimes have been instigated at huge economic cost. There have been repeated occasions when new scientific information or policy clarification has led to enforcement decisions being seen in a new light and current practice continues to evolve. There remain discrepancies between results found pre-harvest and pre-export in some countries, and results from Border Inspection Posts' analyses when consignments arrive at their destination, despite international harmonisation of test methods and quality criteria. Forensic issues around enforcement decisions following laboratory results for non-compliant consignments containing nitrofurans are summarised herein, including those that have been referred for technical appeal to the UK Government Chemist. Current best practice is collated and specific recommendations and suggestions made for the decision-making process in food safety enforcement. We recommend an approach to semicarbazide analysis from core flesh, removal of ice glaze prior to analysis and that measurement uncertainty is subtracted from the mean result to yield a ‘not less than’ figure used for reporting purposes ‘beyond reasonable doubt’. Research is needed to fill knowledge gaps with regard to sample homogeneity and sampling protocols for nitrofurans in food of animal origin. Sampling should be standardised, as has been established for mycotoxin controls and a modern toxicology risk assessment of nitrofurans and their metabolites in food appears to be warranted.

Health risk assessment of exposure to TriCresyl Phosphates (TCPs) in aircraft: A commentary

Possible exposure to TriCresyl Phosphates (TCPs) has led to concerns among airline crew members. One isomer, Tri-ortho-Cresyl Phosphate (ToCP) is known to be neurotoxic and exposure to ToCP via contaminated cabin air has been suggested to be associated with the alleged Aerotoxic syndrome. The symptoms associated with Aerotoxic syndrome are diverse, including headaches, loss of balance, numbness and neurobehavioral abnormalities such as emotional instability, depression and cognitive dysfunction. Other ortho-isomers are toxic as well, but the non-ortho isomers are regarded as less toxic.In a collaborative effort to increase insight into the possible association between exposure to TCPs via contaminated cabin air and Aerotoxic syndrome, we performed an exposure- and toxicological risk assessment. Measurements in KLM 737 aircraft have demonstrated the presence of non-ortho isomers in low concentrations, though ToCP and other ortho-isomers could not be detected. Based on this exposure assessment, we established a toxicological risk model that also takes into account human differences in bioactivation and detoxification to derive a hazard quotient. From this model it appears unlikely that the health effects and alleged Aerotoxic syndrome are due to exposure to ToCP. Alternative explanations for the reported symptoms are discussed, but evaluation of the current findings in light of the criteria for occupational disease leads to the conclusion that the Aerotoxic Syndrome cannot be regarded as such. Additional research is thus required to unravel the underlying causes for the reported health complaints.

Harnessing mathematical models and uncertainty in toxicological risk assessments

Harnessing mathematical models and uncertainty in toxicological risk assessments

Risk assessment approach for e-cigarette flavours

INTRODUCTION Flavours are an important aspect of the e-cigarette sensory experience. The e-cigarette aerosol is generated by a heating coil vapourising the e-liquid. The vapourisation temperature has been estimated to reach up to 350oC [1], higher coil temperatures have been reported in the absence of e-liquid [2]. Our toxicological risk assessment approach to flavours considers both the flavour itself and the identification, measurement and risk assessment of any potential thermal breakdown and/or reaction products.

Assuring safety without animal testing concept (ASAT). Integration of human disease data with in vitro data to improve toxicology testing

According to the Assuring Safety Without Animal Testing (ASAT) principle, risk assessment may ultimately become possible without the use of animals (Fentem et al., (2004). Altern. Lab. Anim. 32, 617-623). The ASAT concept takes human disease mechanisms as starting point and tries to define if activation of these mechanisms by chemical exposure in in vitro models can be used for toxicological risk assessment. The goal of the present research was to study if integration of public data, from human diseases and in vitro toxicology, is possible at the data level. Two human diseases, associated with chemical exposure, were included: human hepatocellular carcinoma and allergic contact dermatitis (ACD). Data were retrieved from expert knowledge and different online sources (e.g. GEO, ArrayExpress) and a Knowledge Base for storage and modelling of the data was established. Using the Knowledge Base for ACD, it was possible to discern sensitizing from non-sensitizing compounds, as defined by enrichment of clinically defined disease gene sets in in vitro genomics datasets. In addition, the strongest sensitizers most profoundly activated these gene sets. During the presentation, the Knowledge Base will be shown. In addition, the ongoing incorporation of (reverse) kinetic modelling to judge the relevance of in vitro concentrations, in relation to realistic in vivo exposure scenarios, will be illustrated. Finally, the expansion towards the development of data models for other disease areas (cholestasis) will be discussed.

Impact of structural and metabolic variations on the toxicity and carcinogenicity of hydroxy- and alkoxy-substituted allyl- and propenylbenzenes.

The metabolic fate of a compound is determined by numerous factors including its chemical structure. Although the metabolic options for a variety of functional groups are well understood and can often provide a rationale for the comparison of toxicity based on structural analogy, at times quite minor structural variations may have major consequences for metabolic outcomes and toxicity. In this perspective, the effects of structural variations on metabolic outcomes is detailed for a group of related hydroxy- and alkoxy-substituted allyl- and propenylbenzenes. These classes of compounds are naturally occurring constituents of a variety of botanical-based food items. The classes vary from one another by the presence or absence of alkylation of their para-hydroxyl substituents and/or the position of the double bond in the alkyl side chain. We provide an overview of how these subtle structural variations alter the metabolism of these important food-borne compounds, ultimately influencing their toxicity, particularly their DNA reactivity and carcinogenic potential. The data reveal that detailed knowledge of the consequences of subtle structural variations for metabolism is essential for adequate comparison of structurally related chemicals. Taken together, it is concluded that predictions in toxicological risk assessment should not be performed on the basis of structural analogy only but should include an analogy of metabolic pathways across compounds and species.

Evidence from pharmacology and pathophysiology suggests that chemicals with dissimilar mechanisms of action could be of bigger concern in the toxicological risk assessment of chemical mixtures than chemicals with a similar mechanism of action

Mathematical models have been developed for the toxicological risk assessment of chemical mixtures. However, exposure data as well as single chemical toxicological data are required for these models. When addressing this data need, it could be attractive to focus on chemicals with similar mechanisms of action, similar modes of action or with common target organs. In the European Union, efforts are currently being made to subgroup chemicals according to this need. However, it remains to be determined whether this is the best strategy to obtain data for risk assessment. In conditions such as cancer or HIV, it is generally recognised that pharmacological combination therapy targeting different mechanisms of action is more effective than a strategy where only one mechanism is targeted. Moreover, in diseases such as acute myocardial infarction and congestive heart failure, several organ systems concomitantly contribute to the pathophysiology, suggesting that a grouping based on common target organs may also be inefficient. A better option may be to prioritise chemicals on the basis of potency and risk of exposure. In conclusion, there are arguments to suggest that we should concomitantly consider all targets that a chemical can affect in the human body and not merely a subset.

The long and winding road of progress in the use of in vitro data for risk assessment purposes: From "carnation test" to integrated testing strategies.

This paper introduces the special issue on quantitative in vitro-in vivo extrapolations (QIVIVE). It highlights important issues in the development of in vitro toxicology towards its implementation in toxicological risk assessment.

Toward better research practice—Shortcomings decreasing the significance of epidemiological studies in the toxicological field

Neurobehavioral studies do not always gain the impact they should have, neither in the scientific nor in the regulatory field of neurotoxicology. Among others, shortcomings and inconsistencies across epidemiological studies may contribute to this situation. Examples were compiled to increase awareness of obstacles for conclusions. Meta-analyses were exploited since they sometimes allow the detection of deficits that are not obvious from individual studies.Exposure assessment, performance measures, and confounding were scrutinized among 98 primary studies included in meta-analyses on mercury, solvents, manganese and pesticides.Inconsistent and hardly comparable markers of exposure were found; figures, units or sampling periods were not always provided. The contribution of test materials to differences in test outcomes across studies could sometimes not be evaluated due to the insufficient description of the employed tests. Hypotheses for the selection of performance variables often remained undisclosed. Matching procedures prevailed with respect to the confounder age; the comparability of groups with respect to intelligence and gender remained more elusive. 8% and 16% of the studies did not even mention confounding from intelligence and gender, respectively. Only one third of the studies provided adjusted means for group comparisons; the proportion was slightly larger for studies published 2000–2010. While 50% of the studies considered confounders for their dose–response assessment, only 29% reported results for the total of test variables.The outlined deficits impede, among others, the assessment of exposure–effect relationships and confounding across studies; thereby they limit the use of the studies for toxicological risk assessment and future prevention. Some shortcomings also impede a deeper insight into the mechanisms of toxicity: tests like the Digit Symbol show that something is affected, but not what is affected. Thorough description of measures employed is among the first consequences from the data. The consideration of mechanistic insights from research on animals and neurobiology may further help to increase the significance of epidemiological studies.