Application of the margin of exposure (MoE) approach to substances in food that are genotoxic and carcinogenic: example: furan (CAS No. 110-00-9)

Risk Assessment of Polycyclic Aromatic Hydrocarbons and Heterocyclic Aromatic Amines in Processed Meat, Cooked Meat and Fish-Based Products Using the Margin of Exposure Approach

Background

The objective of this study is to assess the risk of exposure of polycyclic aromatic hydrocarbons (PAHs) and heterocyclic aromatic amines (HCAs) in meat and fish-based products marketed in Malaysia using the margin of exposure (MOE) approach.

Methods

Benchmark Dose (BMD) software was used to model the BMD at a lower end of a one-sided 95% confidence interval with a 10% incremental risk (BMDL10) of PAHs and HCAs from different target organ toxicities. The MOEs of PAHs and HCAs in meat and fish-based products were determined by utilising the calculated BMDL10 values and estimated daily intake of meat and fish-based products from published data.

Results

The calculated BMDL10 values of PAHs (i.e. benzo[a]pyrene [BaP] and fluoranthene [FA]) and HCAs (i.e. 2-amino-3,8,dimethylimidazo[4,5-f]quinoxaline [MeIQx] and 2-amino-1-methyl-6-phenylimidazo[4,5,6]pyridine [PhIP]) ranged from 19 mg/kg bw/day to 71,801 mg/kg bw/day. The MOE of BaP ranged from 41,895 to 71,801 and that of FA ranged from 19 to 1412. As for MeIQx and PhIP, their MOEs ranged from 6,322 to 7,652 and from 2,362 to 14,390, respectively.

Conclusion

The MOEs of FA, MeIQx and PhIP were lower than 10,000, indicating a high concern for human health and therefore demanding effective risk management actions.

Metabolomic Analysis of Phytochemical Compounds from Ethanolic Extract of Lime (Citrus aurantifolia) Peel and Its Anti-Cancer Effects against Human Hepatocellular Carcinoma Cells

Lime peels are food waste from lime product manufacturing. We previously developed and optimized a green extraction method for hesperidin-limonin-rich lime peel extract. This study aimed to identify the metabolomics profile of phytochemicals and the anti-cancer effects of ethanolic extract of lime (Citrus aurantifolia) peel against liver cancer cells PLC/PRF/5. The extract’s metabolomics profile was analyzed by using LC-qTOF/MS and GC-HRMS. The anti-cancer effects were studied by using MTT assay, Annexin-PI assay, and Transwell-invasion assay. Results show that the average IC50(s) of hesperidin, limonin, and the extract on cancer cells’ viability were 165.615, 188.073, and 503.004 µg/mL, respectively. At the IC50 levels, the extract induced more apoptosis than those of pure compounds when incubating for 24 and 48 h (p < 0.0001). A combination of limonin and hesperidin showed a synergistic effect on apoptosis induction (p < 0.001), but the effect of the combination was still less than that of the extract at 48 h. Furthermore, the extract significantly inhibited cancer cell invasion better than limonin but equal to hesperidin. At the IC50 level, the extract contains many folds lower amounts of hesperidin and limonin than the IC50 doses of the pure compounds. Besides limonin and hesperidin, there were another 60 and 22 compounds detected from the LCMS and GCMS analyses, respectively. Taken altogether, the superior effect of the ethanolic extract against liver cancer cells compared to pure compound likely results from the combinatorial effects of limonin, hesperidin, and other phytochemical components in the extract.

A comprehensive review of furan in foods: From dietary exposures and in vivo metabolism to mitigation measures

Furan is a thermal food processing contaminant that is ubiquitous in various food products such as coffee, canned and jarred foods, and cereals. A comprehensive summary of research progress on furan is presented in this review, including discussion of (i) formation pathways, (ii) occurrence and dietary exposures, (iii) analytical techniques, (iv) toxicities, (v) metabolism and metabolites, (vi) risk assessment, (vii) potential biomarkers, and (viii) mitigation measures. Dietary exposure to furan varies among different countries and age groups. Furan acts through various toxicological pathways mediated by its primary metabolite, cis-2-butene-1,4-dial (BDA). BDA can readily react with glutathione, amino acids, biogenic amines, or nucleotides to form corresponding metabolites, some of which have been proposed as potential biomarkers of exposure to furan. Present risk assessment of furan mainly employed the margin of exposure approach. Given the widespread occurrence of furan in foods and its harmful health effects, mitigating furan levels in foods or exploring potential dietary supplements to protect against furan toxicity is necessary for the benefit of food safety and public health.

Dietary exposure to acrylamide of university students in Ningxia of Northwest China and the effect on their neurobehavioral performance and oxidative stress in serum

This study aims to investigate dietary exposure to acrylamide (AA) and also make an assessment of its effect on the neurobehavioral performance and oxidative stress in the serum of university students in Ningxia. The place primarily consists of arid, dry desert, and wheat-based foods are the staple food there. A total of 803 university students in Ningxia participated in this cross-sectional study. Diet intake of AA was estimated with FFQ. The AA risk was calculated as margin of exposure (MOE) values. NCTB questionnaires were used to assess neurobehavioral performance. The serum oxidative stress levels of the university students were measured as GSH, MDA, and SOD. The mean for AA exposure of university students was 0.515 μg kg^-1 bw day^-1. The highest contributor was traditional Chinese grain products, representing 34.71% of the total daily AA intake. Followed were deep-fried potato products, traditional Western grain products, soft drinks, and nuts, which accounted for 23.87%, 16.59%, 11.15%, and 11%, respectively. The median AA exposure were 480 (BMDL₁₀ = 0.18 mg kg^-1 bw day^-1) and 827 (BMDL₁₀ = 0.31 mg kg^-1 bw day^-1), respectively. The results indicated that diet AA may have an effect on the emotional status and neurobehavior among this population. We observed no significant differences in oxidative stress under the three levels of AA exposure (p > .05). It suggests a health concern for university students in Northwest China that should get society's attention.

Formation of furan in baby food products: Identification and technical challenges

Furan is generally produced during thermal processing of various foods including baked, fried, and roasted food items such as cereal products, coffee, canned, and jarred prepared foods as well as in baby foods. Furan is a toxic and carcinogenic compound to humans and may be a vital hazard to infants and babies. Furan could be formed in foods through thermal degradation of carbohydrates, dissociation of amino acids, and oxidation of polyunsaturated fatty acids. The detection of furan in food products is difficult due to its high volatility and low molecular weight. Headspace solid-phase microextraction coupled with gas chromatography/mass spectrometer (GC/MS) is generally used for analysis of furan in food samples. The risk assessment of furan can be characterized using margin of exposure approach (MOE). Conventional strategies including cooking in open vessels, reheating of commercially processed foods with stirring, and physical removal using vacuum treatment have remained unsuccessful for the removal of furan due to the complex production mechanisms and possible precursors of furan. The innovative food-processing technologies such as high-pressure processing (HPP), high-pressure thermal sterilization (HPTS), and Ohmic heating have been adapted for the reduction of furan levels in baby foods. But in recent years, only HPP has gained interest due to successful reduction of furan because of its nonthermal mechanism. HPP-treated baby food products are commercially available from different food companies. This review summarizes the mechanism involved in the formation of furan in foods, its toxicity, and identification in infant foods and presents a solution for limiting its formation, occurrence, and retention using novel strategies.

Potential Antagonistic Effects of Acrylamide Mitigation during Coffee Roasting on Furfuryl Alcohol, Furan and 5-Hydroxymethylfurfural

The four heat-induced coffee contaminants-acrylamide, furfuryl alcohol (FA), furan and 5-hydroxymethylfurfural (HMF)-were analyzed in a collective of commercial samples as well as in Coffea arabica seeds roasted under controlled conditions from very light Scandinavian style to very dark Neapolitan style profiles. Regarding acrylamide, average contents in commercial samples were lower than in a previous study in 2002 (195 compared to 303 µg/kg). The roasting experiment confirmed the inverse relationship between roasting degree and acrylamide content, i.e., the lighter the coffee, the higher the acrylamide content. However, FA, furan and HMF were inversely related to acrylamide and found in higher contents in darker roasts. Therefore, mitigation measures must consider all contaminants and not be focused isolatedly on acrylamide, specifically since FA and HMF are contained in much higher contents with lower margins of exposure compared to acrylamide.

Scientific opinion of Flavouring Group Evaluation 502 (FGE.502): grill flavour 'Grillin' 5078'

The EFSA Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids (CEF Panel) was requested to deliver a scientific opinion on the implication for human health of the product Grillin’ 5078 [FL‐no: 21.003] in the Flavouring Group Evaluation 502, according to Regulation (EC) No 1331/2008 and Regulation (EC) No 1334/2008 of the European Parliament and of the Council. The product is derived from heat‐treated high oleic sunflower oil and intended to be used as a food flavouring with charbroiled or grilled aroma in a wide variety of food categories either in liquid or powder form. Information on manufacturing and compositional data was considered adequate to show the reproducibility of the production process. However, the Panel noted that a considerable amount of the non‐volatile fraction of the product could not be identified. The chronic dietary exposure to the substance estimated using the Added Portions Exposure Technique (APET) was calculated to be 60 mg/person per day for a 60‐kg adult and 37.8 mg/person per day for a 15‐kg child. The data submitted for evaluating the genotoxic potential of the flavouring was considered insufficient. There are still 12 substances in the flavouring for which the evaluation of genotoxic potential is pending. No toxicity studies have been provided on the final product itself. Only information on a number of constituents of the flavouring and data on toxicity of several thermally treated fats and oils were provided by the applicant. However, the Panel considered the time–temperature conditions that were applied in the preparation of the substances tested as not comparable to those applied in the course of the production of the flavouring. The Panel concluded that on the basis of the data provided by the applicant the safety of Grillin’ 5078 cannot be established.

Scientific Opinion of Flavouring Group Evaluation 500 (FGE.500): rum ether

The Panel on Food Contact Materials, Enzymes, Flavourings and Processing Aids of the European Food Safety Authority was requested to deliver a scientific opinion on the implications for human health of the flavouring rum ether [FL-no: 21.001] in the Flavouring Group Evaluation 500 (FGE.500), according to Regulation (EC) No 1331/2008 and Regulation (EC) No 1334/2008 of the European Parliament and of the Council. Rum ether is a complex mixture of volatile substances obtained by distillation of the reaction products of pyroligneous acid and ethyl alcohol under oxidative conditions in the presence of manganese dioxide and sulfuric acid. A total of 84 volatile constituents have been reported by the applicant. It is a colourless liquid with a rum-like odour and flavour. Its major uses are in the food categories beverages, confectionery and baked goods. The Panel decided to apply a congeneric group-based approach. The 84 reported constituents were allocated to 12 congeneric groups, based on structural and metabolic similarity. For eight of the congeneric groups, the Panel concluded that there is no safety concern at the intended conditions of use. However, the Panel concluded that substances in congeneric group 1 (ethanol and acetaldehyde) and congeneric group 12 (furan) are carcinogenic and genotoxic. The Panel also identified genotoxicity concerns for substances in congeneric group 3 (3-pentene-2-one). The exposure for congeneric group 10 (ethers of various structures) was above the Threshold of Toxicological Concern (TTC) applicable for this group, but a point of departure or health based guidance value that covers all the substances in this group could not be identified. The Panel concluded that according to the overall strategy for the risk assessment of flavouring substances, the presence of genotoxic substances as process-derived constituents of rum ether is of safety concern.

Low dose assessment of the carcinogenicity of furan in male F344/N Nctr rats in a 2-year gavage study

Furan is a volatile organic chemical that is a contaminant in many common foods. Furan is hepatocarcinogenic in mice and rats; however, the risk to humans from dietary exposure to furan cannot be estimated accurately because the lowest tested dose of furan in a 2-year bioassay in rats gave nearly a 100% incidence of cholangiocarcinoma. To provide bioassay data that can be used in preparing risk assessments, the carcinogenicity of furan was determined in male F344/N Nctr rats administered 0, 0.02, 0.044, 0.092, 0.2, 0.44, 0.92, and 2 mg furan/kg body weight (BW) by gavage 5 days/week for 2 years. Exposure to furan was associated with the development of malignant mesothelioma on membranes surrounding the epididymis and on the testicular tunics, with the increase being significant at 2 mg furan/kg BW. There was also a dose-related increase in the incidence of mononuclear cell leukemia, with the increase in incidence being significant at 0.092, 0.2, 0.92, and 2 mg furan/kg BW. Dose-related non-neoplastic liver lesions included cholangiofibrosis, mixed cell foci, basophilic foci, biliary tract hyperplasia, oval cell hyperplasia, regenerative hyperplasia, and cytoplasmic vacuolization. The most sensitive non-neoplastic lesion was cholangiofibrosis, the frequency of which increased significantly at 0.2 mg furan/kg BW.

Toxicogenomics Case Study: Furan

Development of pragmatic methodologies for human health risk assessment is required to address current regulatory challenges. We applied three toxicogenomic approaches—quantitative, predictive, and mechanistic—to a case study in mice exposed for 3 weeks to the hepatocarcinogen furan. We modeled the dose response of a variety of transcriptional endpoints and found that they produced benchmark doses similar to the furan-dependent cancer benchmark doses. Meta-analyses showed strong similarity between furan-dependent gene expression changes and those associated with several hepatic pathologies. Molecular pathways facilitated the development of a molecular mode of action for furan-induced hepatocellular carcinogenicity. Finally, we compared transcriptomic profiles derived from formalin-fixed and paraffin-embedded (FFPE) samples with those from high-quality frozen samples to evaluate whether archival samples are a viable option for toxicogenomic studies. The advantage of using FFPE tissues is that they are very well characterized (phenotypically); the disadvantage is that formalin degrades biomacromolecules, including RNA. We found that FFPE samples can be used for toxicogenomics using a ribo-depletion RNA-seq protocol. Our case study demonstrates the utility of toxicogenomics data to human health risk assessment, the potential of archival FFPE tissue samples, and identifies viable strategies toward the reduction of animal usage in chemical testing.

Toxicogenomic assessment of liver responses following subchronic exposure to furan in Fischer F344 rats

Furan is a widely used industrial chemical and a contaminant in heated foods. Chronic furan exposure causes cholangiocarcinoma and hepatocellular tumors in rats at doses of 2 mg/kg bw/day or greater, with gender differences in frequency and severity. The hepatic transcriptional alterations induced by low doses of furan (doses below those previously tested for induction of liver tumors) and the potential mechanisms underlying gender differences are largely unexplored. We used DNA microarrays to examine the global hepatic mRNA and microRNA transcriptional profiles of male and female rats exposed to 0, 0.03, 0.12, 0.5 or 2 mg/kg bw/day furan over 90 days. Marked gender differences in gene expression responses to furan were observed, with many more altered genes in exposed males than females, confirming the increased sensitivity of males even at the low doses. Pathway analysis supported that key events in furan-induced liver tumors in males include gene expression changes related to oxidative stress, apoptosis and inflammatory response, while pathway changes in females were consistent with primarily adaptive responses. Pathway benchmark doses (BMDs) were estimated and compared to relevant apical endpoints. Transcriptional pathway BMDs could only be examined in males. These median BMDs ranged from 0.08 to 1.43 mg/kg bw/day and approximated those derived from traditional histopathology. MiR-34a (a P53 target) was the only microRNA significantly increased at the 2 mg/kg bw/day, providing evidence to support the importance of apoptosis and cell proliferation in furan hepatotoxicity. Overall, this study demonstrates the use of transcriptional profiling to discern mode of action and mechanisms involved in gender differences.

Selection of appropriate tumour data sets for Benchmark Dose Modelling (BMD) and derivation of a Margin of Exposure (MoE) for substances that are genotoxic and carcinogenic: considerations of biological relevance of tumour type, data quality and uncertainty assessment

This article addresses a number of concepts related to the selection and modelling of carcinogenicity data for the calculation of a Margin of Exposure. It follows up on the recommendations put forward by the International Life Sciences Institute - European branch in 2010 on the application of the Margin of Exposure (MoE) approach to substances in food that are genotoxic and carcinogenic. The aims are to provide practical guidance on the relevance of animal tumour data for human carcinogenic hazard assessment, appropriate selection of tumour data for Benchmark Dose Modelling, and approaches for dealing with the uncertainty associated with the selection of data for modelling and, consequently, the derived Point of Departure (PoD) used to calculate the MoE. Although the concepts outlined in this article are interrelated, the background expertise needed to address each topic varies. For instance, the expertise needed to make a judgement on biological relevance of a specific tumour type is clearly different to that needed to determine the statistical uncertainty around the data used for modelling a benchmark dose. As such, each topic is dealt with separately to allow those with specialised knowledge to target key areas of guidance and provide a more in-depth discussion on each subject for those new to the concept of the Margin of Exposure approach.

Furan in heat-treated foods: formation, exposure, toxicity, and aspects of risk assessment

Furan is formed in a variety of heat-treated foods through thermal degradation of natural food constituents. Relatively high levels of furan contamination are found in ground roasted coffee, instant coffee, and processed baby foods. European exposure estimates suggest that mean dietary exposure to furan may be as high as 1.23 and 1.01 μg/kg bw/day for adults and 3- to 12-month-old infants, respectively. Furan is a potent hepatotoxin and hepatocarcinogen in rodents, causing hepatocellular adenomas and carcinomas in rats and mice, and high incidences of cholangiocarcinomas in rats at doses ≥ 2 mg/kg bw. There is therefore a relatively low margin of exposure between estimated human exposure and doses that cause a high tumor incidence in rodents. Since a genotoxic mode of action cannot be excluded for furan-induced tumor formation, the present exposures may indicate a risk to human health and need for mitigation. This review summarizes the current knowledge on mechanisms of furan formation in food, human dietary exposure to furan, and furan toxicity, and highlights the need to establish the risk resulting from the genotoxic and carcinogenic properties of furan at doses lower than 2 mg/kg bw.

Risk assessment of Belgian adults for furan contamination through the food chain

Risk assessment is an interdisciplinary process used to quantify the risk linked to a hazard. In the present paper it is applied to quantify the risk linked to furan ingestion through the food chain for the Belgian adult population. Two approaches, deterministic and probabilistic, were carried out in parallel. The deterministic method relied on a case study, whereas the probabilistic approach involved statistical distributions of contamination and consumption data to calculate a statistical distribution of the daily intake. First, the deterministic method revealed a low estimated daily intake (EDI) for the average population (380 ng*(kg(bw)*day)⁻¹) and a huge contribution of coffee consumption to the EDI (55%). Increasing or decreasing the daily coffee consumption by one cup can affect the EDI by about 22%. Afterwards, the probabilistic approach showed that the average population has a low EDI (494 ng*(kg(bw)*day)⁻¹), and that high contamination levels were only registered in a small proportion of the population. Finally, a comparison of the RfD(chronic oral) showed that less than 10% of the Belgian population had an EDI above the reference dose proposed by the USEPA; the majority of the population had an EDI 20% below the reference dose. The margin of exposure (MoE) approach indicated that the level of risk related to furan intake through ingestion is low, with a MoE > 10,000 for more than 10% of the population and no result < 100.

Analysis and risk assessment of furan in coffee products targeted to adolescents

The aim of this work was to analyse the furan concentrations in coffee products targeted to adolescents and to estimate the health risk for those consumers by using the consumption data of the Dortmund Nutritional and Anthropometric Longitudinally Designed Study (DONALD). Three different kinds of coffee beverages were analysed: 'coffee ready to drink' (i.e. industrially manufactured and packaged products available in cans or plastic cups), 'coffee instant' (i.e. soluble coffee in powder form) and 'coffee from coffee chains' (i.e. freshly prepared coffee sampled on-site). Furan was analysed according to the US Food and Drug Administration (USFDA) method using headspace-GC-MS and quantification with standard addition. The lowest furan concentrations were found within the category 'coffee instant', with an average of 4.6 µg kg(-1), followed by the category 'coffee ready to drink', with an average of 41.3 µg kg(-1), while the products from the coffee chains showed the highest concentrations, on average 100.5 µg kg(-1). According to the obtained furan contents, it seems that the highest furan exposure for adolescents is generally given in the consumption of products within the category 'coffee from coffee chains', while the lowest is given in the category 'coffee instant'. Risk assessment based on the margin of exposure (MOE) approach showed that in different consumption scenarios except for consumers of instant coffee, the MOE lay below 10,000, a range that is judged to be of public health relevance. The lowest MOE was found for consumers in the age group 10-12 years (especially females) and for both sexes in the age group 16-18 years.

Detailed exposure assessment of dietary furan for infants consuming commercially jarred complementary food based on data from the DONALD study

Furan is a possible human carcinogen regularly occurring in commercially jarred complementary foods. This paper will provide a detailed exposure assessment for babies consuming these foods considering different intake scenarios. The occurrence data on furan in complementary foods were based on our own headspace-gas chromatography/mass spectrometry (HS-GC/MS) analytical results (n = 286). The average furan content in meals and menus was between 20 and 30 µg kg(-1), which is in excellent agreement with results from other European countries. Using measured food consumption data from the Dortmund Nutritional and Anthropometric Longitudinally Designed (DONALD) study, the average exposures for consumers of commercially jarred foods ranged between 182 and 688 ng kg(-1) bw day(-1), with a worst case scenario for P95 consumers ranging between 351 and 1066 ng kg(-1) bw day(-1). The exposure data were then used to characterize risk using the margin of exposure method based on a benchmark dose lower confidence limit for a 10% response (BMDL10) of 1.28 mg kg(-1) bw day(-1) for hepatocellular tumours in rats. The margin of exposures (MOEs) were below the threshold of 10 000, which is often used to define public health risks, in all scenarios, ranging between 7022 and 1861 for average consumers and between 3642 and 1200 for the P95 consumers. Mitigative measures to avoid furan in complementary foods should be of high priority for risk management.

Naturally occurring food toxins

Although many foods contain toxins as a naturally-occurring constituent or, are formed as the result of handling or processing, the incidence of adverse reactions to food is relatively low. The low incidence of adverse effects is the result of some pragmatic solutions by the US Food and Drug Administration (FDA) and other regulatory agencies through the creative use of specifications, action levels, tolerances, warning labels and prohibitions. Manufacturers have also played a role by setting limits on certain substances and developing mitigation procedures for process-induced toxins. Regardless of measures taken by regulators and food producers to protect consumers from natural food toxins, consumption of small levels of these materials is unavoidable. Although the risk for toxicity due to consumption of food toxins is fairly low, there is always the possibility of toxicity due to contamination, overconsumption, allergy or an unpredictable idiosyncratic response. The purpose of this review is to provide a toxicological and regulatory overview of some of the toxins present in some commonly consumed foods, and where possible, discuss the steps that have been taken to reduce consumer exposure, many of which are possible because of the unique process of food regulation in the United States.