Update of the risk assessment of inorganic arsenic in food.

The European Commission asked EFSA to update its 2009 risk assessment on arsenic in food carrying out a hazard assessment of inorganic arsenic (iAs) and using the revised exposure assessment issued by EFSA in 2021. Epidemiological studies show that the chronic intake of iAs via diet and/or drinking water is associated with increased risk of several adverse outcomes including cancers of the skin, bladder and lung. The CONTAM Panel used the benchmark dose lower confidence limit based on a benchmark response (BMR) of 5% (relative increase of the background incidence after adjustment for confounders, BMDL05) of 0.06 µg iAs/kg bw per day obtained from a study on skin cancer as a Reference Point (RP). Inorganic As is a genotoxic carcinogen with additional epigenetic effects and the CONTAM Panel applied a margin of exposure (MOE) approach for the risk characterisation. In adults, the MOEs are low (range between 2 and 0.4 for mean consumers and between 0.9 and 0.2 at the 95th percentile exposure, respectively) and as such raise a health concern despite the uncertainties.

Update of the risk assessment of mineral oil hydrocarbons in food.

Mineral oil hydrocarbons (MOH) are composed of saturated hydrocarbons (MOSH) and aromatic hydrocarbons (MOAH). Due to the complexity of the MOH composition, their complete chemical characterisation is not possible. MOSH accumulation is observed in various tissues, with species-specific differences. Formation of liver epithelioid lipogranulomas and inflammation, as well as increased liver and spleen weights, are observed in Fischer 344 (F344) rats, but not in Sprague-Dawley (SD) rats. These effects are related to specific accumulation of wax components in the liver of F344 rats, which is not observed in SD rats or humans. The CONTAM Panel concluded that F344 rats are not an appropriate model for effects of MOSH with wax components. A NOAEL of 236 mg/kg body weight (bw) per day, corresponding to the highest tested dose in F344 rats of a white mineral oil product virtually free of wax components, was selected as relevant reference point (RP). The highest dietary exposure to MOSH was estimated for the young population, with lower bound-upper bound (LB-UB) means and 95th percentiles of 0.085-0.126 and 0.157-0.212 mg/kg bw per day, respectively. Considering a margin of exposure approach, the Panel concluded that the present dietary exposure to MOSH does not raise concern for human health for all age classes. Genotoxicity and carcinogenicity are associated with MOAH with three or more aromatic rings. For this subfraction, a surrogate RP of 0.49 mg/kg bw per day, calculated from data on eight polycyclic aromatic hydrocarbons, was considered. The highest dietary exposure to MOAH was also in the young population, with LB-UB mean and 95th percentile estimations of 0.003-0.031 and 0.011-0.059 mg/kg bw per day, respectively. Based on two scenarios on three or more ring MOAH contents in the diet and lacking toxicological information on effects of 1 and 2 ring MOAH, a possible concern for human health was raised.

Risk assessment of N-nitrosamines in food.

EFSA was asked for a scientific opinion on the risks to public health related to the presence of N-nitrosamines (N-NAs) in food. The risk assessment was confined to those 10 carcinogenic N-NAs occurring in food (TCNAs), i.e. NDMA, NMEA, NDEA, NDPA, NDBA, NMA, NSAR, NMOR, NPIP and NPYR. N-NAs are genotoxic and induce liver tumours in rodents. The in vivo data available to derive potency factors are limited, and therefore, equal potency of TCNAs was assumed. The lower confidence limit of the benchmark dose at 10% (BMDL10) was 10 µg/kg body weight (bw) per day, derived from the incidence of rat liver tumours (benign and malignant) induced by NDEA and used in a margin of exposure (MOE) approach. Analytical results on the occurrence of N-NAs were extracted from the EFSA occurrence database (n = 2,817) and the literature (n = 4,003). Occurrence data were available for five food categories across TCNAs. Dietary exposure was assessed for two scenarios, excluding (scenario 1) and including (scenario 2) cooked unprocessed meat and fish. TCNAs exposure ranged from 0 to 208.9 ng/kg bw per day across surveys, age groups and scenarios. 'Meat and meat products' is the main food category contributing to TCNA exposure. MOEs ranged from 3,337 to 48 at the P95 exposure excluding some infant surveys with P95 exposure equal to zero. Two major uncertainties were (i) the high number of left censored data and (ii) the lack of data on important food categories. The CONTAM Panel concluded that the MOE for TCNAs at the P95 exposure is highly likely (98-100% certain) to be less than 10,000 for all age groups, which raises a health concern.

Decontamination process for dioxins and dioxin-like PCBs from fish oil and vegetable oils and fats by a physical process with activated carbon.

Following a request from the European Commission, the EFSA Panel on Contaminants in the Food Chain (CONTAM) assessed a decontamination process of fish oils and vegetable oils and fats to reduce the concentrations of dioxins (polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, abbreviated together as PCDD/Fs) and dioxin-like polychlorinated biphenyls (DL-PCBs) by adsorption to activated carbon. All feed decontamination processes must comply with the acceptability criteria specified in the Commission Regulation (EU) 2015/786. Data provided by the feed food business operator (FBO) were assessed for the efficacy of the process and to demonstrate that the process did not adversely affect the characteristics and properties of the product. The limited information provided, in particular on the analysis of the samples before and after decontamination, did not allow the CONTAM Panel to conclude whether or not the proposed decontamination process is effective in reducing PCDD/Fs and DL-PCBs in the fish- and vegetable oils and fats. Although there is no evidence from the data provided that the decontamination process leads to detrimental changes in the nutritional composition of the fish- and vegetable oils, it is possible that the process could deplete some beneficial constituents (e.g. vitamins). Taken together, it was not possible for the CONTAM Panel to conclude that the decontamination process as proposed by the FBO is compliant with the acceptability criteria provided for in Commission Regulation (EU) 2015/786 of 19 May 2015.

Update of the risk assessment of nickel in food and drinking water.

The European Commission asked EFSA to update its previous Opinion on nickel in food and drinking water, taking into account new occurrence data, the updated benchmark dose (BMD) Guidance and newly available scientific information. More than 47,000 analytical results on the occurrence of nickel were used for calculating chronic and acute dietary exposure. An increased incidence of post-implantation loss in rats was identified as the critical effect for the risk characterisation of chronic oral exposure and a BMDL 10 of 1.3 mg Ni/kg body weight (bw) per day was selected as the reference point for the establishment of a tolerable daily intake (TDI) of 13 µg/kg bw. Eczematous flare-up reactions in the skin elicited in nickel-sensitised humans, a condition known as systemic contact dermatitis, was identified as the critical effect for the risk characterisation of acute oral exposure. A BMDL could not be derived, and therefore, the lowest-observed-adverse-effect-level of 4.3 µg Ni/kg bw was selected as the reference point. The margin of exposure (MOE) approach was applied and an MOE of 30 or higher was considered as being indicative of a low health concern. The mean lower bound (LB)/upper bound (UB) chronic dietary exposure was below or at the level of the TDI. The 95th percentile LB/UB chronic dietary exposure was below the TDI in adolescents and in all adult age groups, but generally exceeded the TDI in toddlers and in other children, as well as in infants in some surveys. This may raise a health concern in these young age groups. The MOE values for the mean UB acute dietary exposure and for the 95th percentile UB raises a health concern for nickel-sensitised individuals. The MOE values for an acute scenario regarding consumption of a glass of water on an empty stomach do not raise a health concern.

Risk assessment of aflatoxins in food.

EFSA was asked to deliver a scientific opinion on the risks to public health related to the presence of aflatoxins in food. The risk assessment was confined to aflatoxin B1 (AFB1), AFB2, AFG1, AFG2 and AFM1. More than 200,000 analytical results on the occurrence of aflatoxins were used in the evaluation. Grains and grain-based products made the largest contribution to the mean chronic dietary exposure to AFB1 in all age classes, while 'liquid milk' and 'fermented milk products' were the main contributors to the AFM1 mean exposure. Aflatoxins are genotoxic and AFB1 can cause hepatocellular carcinomas (HCCs) in humans. The CONTAM Panel selected a benchmark dose lower confidence limit (BMDL) for a benchmark response of 10% of 0.4 µg/kg body weight (bw) per day for the incidence of HCC in male rats following AFB1 exposure to be used in a margin of exposure (MOE) approach. The calculation of a BMDL from the human data was not appropriate; instead, the cancer potencies estimated by the Joint FAO/WHO Expert Committee on Food Additives in 2016 were used. For AFM1, a potency factor of 0.1 relative to AFB1 was used. For AFG1, AFB2 and AFG2, the in vivo data are not sufficient to derive potency factors and equal potency to AFB1 was assumed as in previous assessments. MOE values for AFB1 exposure ranged from 5,000 to 29 and for AFM1 from 100,000 to 508. The calculated MOEs are below 10,000 for AFB1 and also for AFM1 where some surveys, particularly for the younger age groups, have an MOE below 10,000. This raises a health concern. The estimated cancer risks in humans following exposure to AFB1 and AFM1 are in-line with the conclusion drawn from the MOEs. The conclusions also apply to the combined exposure to all five aflatoxins.

Risk assessment of ochratoxin A in food.

The European Commission asked EFSA to update their 2006 opinion on ochratoxin A (OTA) in food. OTA is produced by fungi of the genus Aspergillus and Penicillium and found as a contaminant in various foods. OTA causes kidney toxicity in different animal species and kidney tumours in rodents. OTA is genotoxic both in vitro and in vivo; however, the mechanisms of genotoxicity are unclear. Direct and indirect genotoxic and non-genotoxic modes of action might each contribute to tumour formation. Since recent studies have raised uncertainty regarding the mode of action for kidney carcinogenicity, it is inappropriate to establish a health-based guidance value (HBGV) and a margin of exposure (MOE) approach was applied. For the characterisation of non-neoplastic effects, a BMDL 10 of 4.73 µg/kg body weight (bw) per day was calculated from kidney lesions observed in pigs. For characterisation of neoplastic effects, a BMDL 10 of 14.5 µg/kg bw per day was calculated from kidney tumours seen in rats. The estimation of chronic dietary exposure resulted in mean and 95th percentile levels ranging from 0.6 to 17.8 and from 2.4 to 51.7 ng/kg bw per day, respectively. Median OTA exposures in breastfed infants ranged from 1.7 to 2.6 ng/kg bw per day, 95th percentile exposures from 5.6 to 8.5 ng/kg bw per day in average/high breast milk consuming infants, respectively. Comparison of exposures with the BMDL 10 based on the non-neoplastic endpoint resulted in MOEs of more than 200 in most consumer groups, indicating a low health concern with the exception of MOEs for high consumers in the younger age groups, indicating a possible health concern. When compared with the BMDL 10 based on the neoplastic endpoint, MOEs were lower than 10,000 for almost all exposure scenarios, including breastfed infants. This would indicate a possible health concern if genotoxicity is direct. Uncertainty in this assessment is high and risk may be overestimated.

Editor's Highlight: Differential Effects of Exposure to Single Versus a Mixture of Endocrine-Disrupting Chemicals on Steroidogenesis Pathway in Mouse Testes.

Endocrine-disrupting chemicals (EDCs) generate reproductive dysfunctions affecting the biosynthesis of steroid hormones and genes of the steroidogenic pathway. EDCs effects are mainly reported as a result of exposure to single compounds. However, humans are environmentally exposed to a mixture of EDCs. Herein, we assess chronic exposure to single alkylphenols and phthalates versus a mixture in mouse testes histology and steroidogenesis. Pregnant mice were exposed through drinking water to: 0.3 mg/kg-body weight (BW)/d of each phthalate (bis (2-ethylhexyl) phthalate, dibutyl phthalate, benzyl butyl phthalate), 0.05 mg/kg-BW/d of each alkylphenol (4-nonylphenol, 4-tert-octylphenol), or their mixture, covering from 0.5 postcoital day to weaning, continuing in the male offspring each exposure until adulthood (60-days old). Body and relative testis weight were increased in mixture-exposed mice along with histological alterations. Intratesticular testosterone (T) changed only in mice exposed to DBP, whereas estradiol (E2) levels were altered in all groups (except benzyl butyl phthalate). mRNA levels of genes encoding hormones of the steroid pathway (Cyp11a1, Hsd3b1, Cyp17a1, and Cyp19a1), cholesterol transporters (Star), and transcriptional factors (Sp1) showed that mice exposed to single or mixed compounds had alterations in at least 2 transcripts. However, none of the different types of exposure induced changes in all transcripts. In addition, changes at the mRNA or protein levels with single compounds were not always the same as those with a mixture. In conclusion, the effects of a chronic exposure to a mixture of EDCs on the expression of genes and proteins of the steroidogenic pathway and hormonal status were different from those exposed to single EDC.

Chronic low-dose exposure to a mixture of environmental endocrine disruptors induces microRNAs/isomiRs deregulation in mouse concomitant with intratesticular estradiol reduction.

Humans are environmentally exposed not only to single endocrine-disrupting chemicals (EDCs) but to mixtures that affect their reproductive health. In reproductive tissues, microRNAs (miRNAs) are emerging as key targets of EDCs. Here, we analysed changes in the testis "miRNome" (and their biogenesis mechanism) in chronically exposed adult mice to a cocktail of five EDCs containing 0.3 mg/kg-body weight (BW)/day of each phthalate (DEHP, DBP, BBP) and 0.05 mg/kg-BW/day of each alkylphenol (NP, OP), from conception to adulthood. The testis "miRNome" was characterised using next-generation sequencing (NGS). Expression levels of genes involved in miRNA biogenesis were measured by RT-qPCR, as well as several physiological and cytological parameters. We found two up-regulated, and eight down-regulated miRNAs and thirty-six differentially expressed isomiRs along with an over-expression of Drosha, Adar and Zcchc11. A significant decrease of intratesticular estradiol but not testosterone was detected. Functional analysis showed altered spermatogenesis, germ cell apoptosis and negative correlation of miR-18a-5p with Nr1h2 involved in the deregulation of the steroidogenesis pathway. Here, we present the first association between miRNA/isomiRs deregulation, their mechanisms of biogenesis and histopathological and hormonal alterations in testes of adult mice exposed to a mixture of low-dose EDCs, which can play a role in male infertility.

Endocrine disruptors, gene deregulation and male germ cell tumors.

Endocrine disruptors (EDs) belong to a large group of compounds, usually present as environmental pollutants, which can alter the homeostasis of living organisms by modifying hormonal balance and changing the normal patterns of gene regulation during development and cell differentiation. Hence, the development of male gonads and their functionality may be affected by exposure to specific EDs or their mixtures. The molecular mechanisms of action of these reprotoxicants leading to pathologies of the reproductive system such as testicular cancer, are complex and not well characterized. It is likely, however, that these compounds alter the interaction between the mechanisms of gene regulation and functional gene networks in windows of risk, mainly during embryonic development. Moreover, such changes could be transmitted through generations by epigenetic mechanisms. There are examples of the action of EDs on the expression of mRNAs, small non-coding RNAs and epigenetic marks in the developing testis associated with cellular and molecular alterations found in germ cell tumors. In the present review, we will discuss various aspects of genetic, transcriptomic and epigenetic changes related to testicular development, exposure to EDs and the occurrence of germ cell tumors.

Reprogramming of microRNAs by adenosine-to-inosine editing and the selective elimination of edited microRNA precursors in mouse oocytes and preimplantation embryos.

Adenosine deaminases-acting-on-RNA (ADAR) proteins induce adenosine-to-inosine editing in double-stranded RNA molecules. This editing generates RNA diversity at the post-transcriptional level, and it has been implicated in the control of cell differentiation and development. The editing of microRNA (miRNA) precursors, along with Tudor-SN (Snd1) activity, could lead to the elimination of selected miRNAs and reprogram miRNA activity. Here, we report the dynamics of adenosine-to-inosine editing in miRNA precursors and their selected elimination during mouse preimplantation development. Adar1p110 and Snd1 were found to be strongly but differentially expressed in oocytes and zygotes with respect to later pre-implantation stages. When the biogenesis of miR-151 was assessed, the majority of miR-151 precursors was edited and subsequently eliminated during early development. Deep sequencing of this and other miRNAs confirmed that, in general, edited precursors were selectively eliminated at early post-zygotic stages. Moreover, in oocytes and throughout the zygote-to-blastocyst stages, Tudor-SN accumulated in newly discovered aggregates termed 'T bodies'. These results provide new insight into how editing and Tudor-SN-mediated elimination of miRNA precursors is regulated during early development.

Gene silencing by RNAi in mouse Sertoli cells.

BACKGROUND: RNA interference (RNAi) is a valuable tool in the investigation of gene function. The purpose of this study was to examine the availability, target cell types and efficiency of RNAi in the mouse seminiferous epithelium. METHODS: The experimental model was based on transgenic mice expressing EGFP (enhanced green fluorescent protein). RNAi was induced by in vivo transfection of plasmid vectors encoding for short hairpin RNAs (shRNAs) targeting EGFP. shRNAs were transfected in vivo by microinjection into the seminiferous tubules via the rete testis followed by square wave electroporation. As a transfection reporter, expression of red fluorescent protein (HcRed 1) was used. Cell types, the efficiency of both transfections and RNAi were all evaluated. RESULTS: Sertoli cells were the main transfected cells. A reduction of about 40% in the level of EGFP protein was detected in cells successfully transfected both in vivo and in vitro. However, the efficiency of in vivo transfection was low. CONCLUSION: In adult seminiferous epithelial cells, in vivo post-transcriptional gene silencing mediated by RNAi via shRNA is efficient in Sertoli cells. Similar levels of RNAi were detected both in vivo and in vitro. This also indicates that Sertoli cells have the necessary silencing machinery to repress the expression of endogenous genes via RNAi.

Deregulation of gene expression in fetal oocytes exposed to doxorubicin.

Doxorubicin is an effective anticancer drug but its use is limited due to its adverse side effects such as infertility and cardiomyopathy. Some possible mechanisms of the action of doxorubicin have been postulated, but the initial gene deregulation response has not been investigated. Fetal life stages are critical periods in mammalian oogenesis. This study analyzes gene expression alterations in mouse fetal oocytes exposed in vitro to this anticancer agent. cDNA libraries were generated from isolated fetal oocytes and differential screenings performed with cDNAs from in vitro doxorubicin-treated and -untreated oocytes. Differentially expressed genes were assessed by real-time RT-PCR to quantify the extent of their transcriptional control in doxorubicin-exposed oocytes. The results show that doxorubicin alters the expression of genes involved in the mitochondrial respiratory chain, intracellular transport and cell differentiation. Finally, the up-regulation of a differentially expressed gene (metaxin) mediated by its promoter was evaluated in a functional assay. When treated with doxorubicin, somatic cells transfected with a genetic construct including the promoter of metaxin and a reporter gene showed increases in expression similar to those observed in fetal oocytes. This demonstrates the direct effect of agent on the regulation of a specific gene.

Ran GTPase expression during early development of the mouse embryo.

Ran is a small GTP-binding protein involved in several essential roles for cell viability. This observation implies Ran might be ubiquitously expressed during development. However, Ran shows a differentiated expression pattern that is restricted to specific tissues from embryo to adult. At early embryonic stages of mouse development we found persistent Ran expression in proliferating neural tissue, neural crest derived dorsal root ganglions and sensory pits. We also showed an accumulation of Ran transcripts in main embryonic haematopoietic tissues: blood islands first and then hepatic bud. In advanced stages of development Ran is also expressed in other tissues showing a high cell turnover.