The Cumulative Risk Assessment of Hepatotoxic Chemicals: A Hepatic Histopathology Perspective

Critical appraisal of the expert knowledge elicitation (EKE) methodology to identify uncertainties in building cumulative assessment groups for craniofacial alterations

The European Food Safety Authority (EFSA) conducted a retrospective cumulative dietary risk assessment (CRA) on active substances (AS) and metabolites included in the plant protection products registered in Europe which could provoke craniofacial alterations. Two Cumulative Assessment groups (CAGs) were established: one for alterations due to abnormal skeletal development (CAG-DAC) and one for head soft tissue alterations and brain neural tube defects (CAG-DAH). The probability that each substance is correctly assigned to the specific CAGs (CAG-membership probability) was assessed using weight of evidence and expert knowledge elicitation (EKE) techniques conducted for the six substances identified as risk drivers in each CAG. Four out of the six substances allocated to the CAG-DAC or to the CAG-DAH presented a large interval of uncertainty, with probability of belonging to the attributed CAG between 10 % and 70 % or 33-90 %, which makes it difficult to determine if the substances truly belong to the CAG. In the present work the probability ranges of each risk driver were reassigned according to the approximate probability scale recommended in the EFSA guidance on uncertainty analysis. It is proposed that AS with a high probability are to be included in the CAG and those with a low probability removed from the CAG. For compounds with very large probability ranges, uncertainty assessments would have to be redone to reach narrower probability ranges. Finally, whenever recent decisions on reproduction toxicity classifications made by the European Chemical Agency (ECHA) are available, these should be used to conclude on CAG memberships.

Cumulative risk assessment of dietary exposure of the adult population in Serbia to pesticides that have chronic effects on the thyroid gland through fresh fruits and vegetables

In contrast to the traditional approach to risk assessment, which focuses on a single chemical, cumulative exposure and risk assessment considers the consequences of exposure to multiple chemical combinations. A cumulative risk assessment of dietary exposure of adult females and adult males to pesticides with chronic effects on the thyroid was conducted by estimation of the Total Margin of Exposure (MOET). Exposure to each active substance was estimated using a second-order Monte Carlo simulation. Input values for the simulation were based on over 2300 conventionally produced fruit and vegetable samples analysed from 2021 to 2023 and consumption data collected using the Food Frequency Questionnaire (FFQ) and 24h recall method. MOET values, for both populations assessed, did not exceed thresholds for regulatory consideration established by risk managers. Considering that MOETs values from consumption of fresh fruits and vegetables were relatively close to the threshold value, total exposure to the pesticides could likely reach risk-associated MOET levels, through the consumption of other food products that may be contaminated.

Basic concepts of mixture toxicity and relevance for risk evaluation and regulation

Exposure to multiple substances is a challenge for risk evaluation. Currently, there is an ongoing debate if generic "mixture assessment/allocation factors" (MAF) should be introduced to increase public health protection. Here, we explore concepts of mixture toxicity and the potential influence of mixture regulation concepts for human health protection. Based on this analysis, we provide recommendations for research and risk assessment. One of the concepts of mixture toxicity is additivity. Substances may act additively by affecting the same molecular mechanism within a common target cell, for example, dioxin-like substances. In a second concept, an "enhancer substance" may act by increasing the target site concentration and aggravating the adverse effect of a "driver substance". For both concepts, adequate risk management of individual substances can reliably prevent adverse effects to humans. Furthermore, we discuss the hypothesis that the large number of substances to which humans are exposed at very low and individually safe doses may interact to cause adverse effects. This commentary identifies knowledge gaps, such as the lack of a comprehensive overview of substances regulated under different silos, including food, environmentally and occupationally relevant substances, the absence of reliable human exposure data and the missing accessibility of ratios of current human exposure to threshold values, which are considered safe for individual substances. Moreover, a comprehensive overview of the molecular mechanisms and most susceptible target cells is required. We conclude that, currently, there is no scientific evidence supporting the need for a generic MAF. Rather, we recommend taking more specific measures, which focus on compounds with relatively small ratios between human exposure and doses, at which adverse effects can be expected.

Commentary: cumulative risk assessment of perfluoroalkyl carboxylic acids and perfluoralkyl sulfonic acids: what is the scientific support for deriving tolerable exposures by assembling 27 PFAS into 1 common assessment group?

This commentary proposes an approach to risk assessment of mixtures of per- and polyfluorinated alkyl substances (PFAS) as EFSA was tasked to derive a tolerable intake for a group of 27 PFAS. The 27 PFAS to be considered contain different functional groups and have widely variable physicochemical (PC) properties and toxicokinetics and thus should not treated as one group based on regulatory guidance for risk assessment of mixtures. The proposed approach to grouping is to split the 27 PFAS into two groups, perfluoroalkyl carboxylates and perfluoroalkyl sulfonates, and apply a relative potency factor approach (as proposed by RIVM) to obtain two separate group TDIs based on liver toxicity in rodents since liver toxicity is a sensitive response of rodents to PFAS. Short chain PFAS and other PFAS structures should not be included in the groups due to their low potency and rapid elimination. This approach is in better agreement with scientific and regulatory guidance for mixture risk assessment.

Beneficial effects of coconut oil (Cocos nucifera) on hematobiochemicl and histopathological markers in CCL4-intoxicated rabbits

The study was designed to investigate the effect of Coconut Oil on the levels of some liver and hematological parameters in carbon tetrachloride intoxicated rabbits. Also the antioxidant capacity of Coconut Oil for various concentrations was assessed on the basis of percent scavenging of (DPPH) free radical. Experimental animals were divided into five groups, eight rabbits in each group. These were: group A (Normal control), group B (Toxic control), group C (Standard control), group D (Treated with Coconut Oil 50 mL/kg body weight after CCl4 intoxication), group E (Treated with Coconut Oil 200 mL/kg body weight after CCl4 intoxication). The effects observed were compared with a standard hepatoprotective drug silymarine (50 mL/kg body weight). The Coconut Oil (200 mL/kg body weight) significantly (P<0.05) reduced the elevated serum levels of alanine transaminase (ALT), aspartate transaminase (AST) and alkaline phosphatase (ALP) when compared to a toxic control rabbits. The results of extract treated rabbits were similar to silymarine administered rabbits group. Treatment with Coconut Oil root and silymarine caused no significant changes in RBC, Platelets, (Hb), (MCH) concentration and (HCT) values. However, significant (P<0.05) increase was observed in the total WBC count. The present study suggested that Coconut Oil can be used as an herbal alternative (need further exploration i.e to detect its bioactive compound and its efficacy) for hepatoprotective activity.

Chemical Mixture Calculator - A novel tool for mixture risk assessment

Humans are continuously exposed to complex chemical mixtures from foods and the environment. Experimental models in vivo and in vitro have increased our knowledge on how we can predict mixture effects. To accommodate a need for tools for efficient mixture risk assessment across different chemical classes and exposure sources, we have developed fit-for-purpose criteria for grouping of chemicals and a web-based tool for mixture risk assessment. The Chemical Mixture Calculator (available at www.chemicalmixturecalculator.dk) can be used for mixture risk assessment or identification of main drivers of risk. The underlying database includes hazard and exposure estimates for more than 200 chemicals in foods and environment. We present a range of cumulative assessment groups for effects on haematological system, kidney, liver, nervous system, developmental and reproductive system, and thyroid. These cumulative assessment groups are useful for grouping of chemicals at several levels of refinement depending on the question addressed. We present a mixture risk assessment case for phthalates, evaluated with and without contributions from other chemicals with similar effects. This case study shows the usefulness of the tool as a starting point for mixture risk assessment by the risk assessor, and emphasizes that solid scientific insight regarding underlying assumptions and uncertainties is crucial for result interpretation.

A flow scheme for cumulative assessment of pesticides for adverse liver effects

The European Food Safety Authority (EFSA) is developing approaches to cumulative risk assessment by assigning pesticides to cumulative assessment groups (CAGs). For assignment to CAGs, EFSA relies on common toxic effects (CTEs) on the target system. The developed flow scheme for assignment to liver CAGs sequentially assesses the consistency of the CTE, its adversity, its potential to be secondary to other toxicities, its human relevance, and the relation of the NOAEL for the CTE to the overall NOAEL. If the responses to all questions are "yes", allocation to a CAG is supported; "no" stops the process.