Risk Assessment of Furan Exposure in the Norwegian Population

The Norwegian Scientific Committee for Food Safety (Vitenskapskomiteen for mattrygghet, VKM) has on request of The Norwegian Food Safety Authority performed a risk assessment of furan intake in the Norwegian population based on the most recent national food consumption surveys. National occurrence data of furan concentrations in food were preferentially used in the risk assessment. When national data were lacking, VKM has used occurrence data of furan from other countries. The assessment has been performed by the VKM Panel on Food Additives, Flavourings, Processing Aids, Materials in Contact with Food and Cosmetics and the VKM Panel on Contaminants.   Furan is a volatile and lipophilic compound formed in a variety of heat-treated commercial foods and contributes to the sensory properties of the product. The substance has been found in a number of foods such as coffee, canned and jarred foods including baby food containing meat and various vegetables. High concentrations of furan have been found in coffee and the presence of furan in jarred baby food and infant formulae has received much attention since such products may be the sole diet for many infants. The occurrence of furan in a variety of foods suggests that there are multiple routes of furan formation rather than a single mechanism.   The Norwegian Food Safety Authority has in 2008 and 2009 collected data on furan concentrations in different food products sold on the Norwegian market (Norwegian Food Safety Authority, 2008). In 2011, the Norwegian Food Safety Authority also decided to analyse commercial porridges for infants and children sold on the Norwegian market, to see if furan could be detected in such products.   The calculated furan exposures from food and beverages are based on data from the nationally representative food consumption surveys; Spedkost, Småbarnskost, Ungkost and Norkost. The consumption for each relevant food or food category in the dietary surveys were multiplied with the corresponding mean furan concentrations and totalled for each individual.   The liver is the main target organ for furan toxicity both in mice and rats, but the rat is the most sensitive species. A dose-dependent increase in hepatocellular adenomas and carcinomas was observed in mice and rats, and an increase in the incidence of cholangiocarcinomas was observed in rat liver. Cholangiocarcinomas in male and female rats were the most sensitive toxicological end point observed in rodents. On the basis of the available data, VKM considers that rat cholangiocarcinomas may be relevant for assessing human risk from furan.   Available in vivo data with furan indicate that a reactive metabolite, most likely cis-2-butene1,4-dial (BDA), is formed and that this metabolite can react with DNA and induce mutations. To VKM’s knowledge, no in vivo studies on genotoxicity of BDA have been performed, but BDA was found to be genotoxic in several in vitro tests. VKM therefore considers that a genotoxic mechanism in furan-induced carcinogenesis cannot be excluded and the substance was assessed as a genotoxic carcinogen.   VKM used the Margin of Exposure (MOE) approach in this risk assessment. The suitability of different studies on cholangiocarcinomas for dose-response modelling was considered. The 9-month interim evaluation of a 2-year study from NTP (1993) was chosen because it demonstrates a dose-response relationship. From this study, a point of departure of 0.02 mg/kg bw/day was chosen, based on a benchmark dose lower bound (BMDL10) of 0.14 mg furan/kg bw/day and a correction factor of 7 for shorter than full life-time (2 years) study duration.    For 6-, 12- and 24-month-old children, the main source of furan exposure is jarred baby food. For 4-, 9- and 13-year-old children, the major food source to the furan exposure is breakfast cereals. In adults, the major contribution to the furan exposure is coffee. The highest furan exposure was calculated for 12-month-old infants and ranged from 0.62-1.51 µg/kg bw/day. In adults the furan exposure ranged from 0.27-0.82 µg/kg bw/day.    For mean exposure among infants, children and adolescents, the MOE-values ranged from 29 in 12-month-infants to 2000 in the 13-year-old adolescents. Among high consumers in these groups, the MOE-values ranged from 13 to 400. In adults, the corresponding MOE-values ranged from 59 to 74 for mean furan exposure and from 24 to 26 for high exposure.   It should be noted that this risk assessment of furan contains notable uncertainties and limitations. The use of the 9-month interim study in rats including a correction factor of 7 to derive a point of departure, instead of a full life-time study (2-year) study, likely overestimates the hazard of furan. A possible over-diagnosis of the cholangiocarcinomas, due to the similarities in histopathology between cholangiofibrosis and cholangiocarcinomas in rats, may overestimate the hazard. There are also limitations in assessing food consumption and furan content in foods, leading to uncertainties in estimation of furan exposure.   VKM considers that the current exposure to furan in all age groups, particularly among infants and children, is of health concern.

Natural mixtures of POPs affected body weight gain and induced transcription of genes involved in weight regulation and insulin signaling

Obesity is reaching epidemic proportions worldwide, and is associated with chronic illnesses such as diabetes, cardiovascular disease, hypertension and dyslipidemias (metabolic syndrome). Commonly held causes of obesity are overeating coupled with a sedentary lifestyle. However, it has also been postulated that exposure to endocrine disrupting chemicals (EDCs) may be related to the significant increase in the prevalence of obesity and associated diseases. In the present study, developmental and reproductive effects of lifelong exposure to environmentally relevant concentrations of two natural mixtures of persistent organic pollutants (POPs) were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway (Lake Mjøsa and Lake Losna). The concentration of POPs in the zebrafish ranged from levels detected in wild fish (Lake Mjøsa and Lake Losna), to concentrations reported in human and wildlife populations. Phenotypic effects observed in both exposure groups included (1) earlier onset of puberty, (2) elevated male/female sex ratio, and (3) increased body weight at 5 months of age. Interestingly, genome-wide transcription profiling identified functional networks of genes, in which key regulators of weight homeostasis (PPARs, glucocoricoids, CEBPs, estradiol), steroid hormone functions (glucocoricoids, estradiol, NCOA3) and insulin signaling (HNF4A, CEBPs, PPARG) occupied central positions. The increased weight and the regulation of genes associated with weight homeostasis and insulin signaling observed in the present study suggest that environmental pollution may affect the endocrine regulation of the metabolism, possibly leading to increased weight gain and obesity.

Natural mixtures of persistent organic pollutants (POP) increase weight gain, advance puberty, and induce changes in gene expression associated with steroid hormones and obesity in female zebrafish

In the present study, developmental and reproductive effects of lifelong exposure to environmental relevant concentrations of two natural mixtures of persistent organic pollutants (POP) were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway: one mixture with high levels and one mixture with background levels of polybrominated diphenyl ethers (PBDE), polychlorinated biphenyls (PCB), and dichlorodiphenyltrichloroethane metabolites (DDT). The concentration of POP measured in the zebrafish ranged from levels detected in wild fish from Lake Mjøsa to concentrations reported in human and wildlife populations, indicating that the experimental fish were exposed to concentrations comparable with wild fish. Phenotypic effects observed in both exposure groups included earlier onset of puberty, increased male/female sex ratio, and differences in body weight at 5 mo of age. Interestingly, genome-wide transcription profiling showed changes in regulation of genes involved in endocrine signaling and growth. The transcriptomics changes include key regulator genes for steroid hormone functions (ncoa3), and growth (c/ebp, ncoa3). The effects observed in the experimental zebrafish model raise the question whether chemical pollution represents a risk to reproductive health of wild fish inhabitating the freshwater system.

Transcriptional regulation in liver and testis associated with developmental and reproductive effects in male zebrafish exposed to natural mixtures of persistent organic pollutants (POP)

Persistent organic pollutants (POP) occur as mixtures in nature and it is difficult to predict the toxicity of such mixtures based on knowledge about toxicity and mechanisms of action for single compounds. The present knowledge on the combined toxic effects and modes of actions of exposure to mixtures is limited. Thus, the scientifically based hazard and risk assessment of POP requires analytical and toxicological data from studies with environmental mixtures of POP. The application of genome wide transcription profiling in toxicology, in combination with classical endpoints, will improve the current understanding of the mechanisms of toxic processes. Furthermore, gene expression data may be useful in establishing new hypothesis and discovering new biomarkers for known toxicity as well as not yet recognized toxicity endpoints. In the present study, developmental and reproductive effects of lifelong exposure to environmental relevant concentrations of two natural mixtures of POP were investigated using classical and molecular methods in a controlled zebrafish model. The mixtures used were extracted from burbot (Lota lota) liver originating from freshwater systems in Norway: one mixture with high levels and one mixture with background levels of polybrominated diphenyl ethers (PBD), polychlorinated biphenyls (PCB), and DDT. The concentration of POP in the zebrafish ranged from levels detected in wild fish from Lake Mjøsa, to concentrations reported in human and wildlife populations. Phenotypic effects observed in both exposure groups included (1) reduced survival, (2) earlier onset of puberty, (3) increased male/female sex ratio, and (4) differences in body weight at 5 mo of age. Interestingly, genome-wide transcription profiling showed changes in regulation of genes involved in endocrine signaling and growth. The transcriptomics changes included (1) key regulator genes for steroid and thyroid hormone functions (cga, ncoa3), (2) insulin signaling and metabolic homeostasis (pik3r1, pfkfb3, ptb1), and (3) p53 activation (mdm4). The effects observed in the experimental zebrafish model raise the question of whether chemical pollution represents a risk to the reproductive health of wild fish inhabiting the freshwater system.

Estrogenic effects of selected hydroxy polychlorinated biphenyl congeners in primary culture of Atlantic Salmon (Salmo salar) hepatocytes

Many persistent organic pollutants are known to have endocrine-disrupting effects in several aquatic and terrestrial species. In this regard, hydroxylated metabolites of polychlorinated biphenyls (OH-PCBs) represent serious health and environmental concern because they are shown to act agonistic or antagonistic at hormone receptors (HRs) or to cause hormone-receptor-mediated responses. In the present study, salmon primary hepatocytes were used to study alterations in an estrogen signaling pathway resulting from exposure to four hydroxylated (4OH-CB 107, 4OH-CB146, 4OH-CB187, and 3OH-CB138) metabolites of PCB at different concentrations using quantitative real-time polymerase chain reaction. The effects of the PCB metabolites were compared to the mRNA expression in 17alpha-ethynylestradiol (EE2)-treated cells. Concentration-specific increase of vitellogenin (Vtg) mRNA transcription after exposure to OH-PCBs was observed. Decreased mRNA transcription was observed for zona radiata protein (Zr-protein) and cytochrome P450 side-chain cleavage (P450scc) enzyme. For estrogen receptor beta (ERbeta), the mRNA expression pattern was OH-PCB-metabolite congener-specific. A novel aspect of this study is that OH-PCBs produced effects on hepatic steroidogenic pathways by targeting the StAR protein and P450scc genes. Given that endocrine toxicology research mainly has focused on estrogenicity involving direct ER-mediated effects and that steroidogenic enzyme and proteins are highly tissue- and cell-type-specific and controlled by different promoters and second-messenger pathways, the present findings provide potential new targets for interaction with xenobiotics such as hydroxylated congeners of certain chemicals. The quantitative expression patterns of hepatic and extrahepatic steroidogenic genes and proteins after exposure to environmental contaminants are the subject of systematic investigations in our laboratory.

In vitro reproductive toxicity of polychlorinated biphenyl congeners 153 and 126

This study was conducted to investigate the applicability of an in vitro technique for maturation, fertilization, cleavage, and growth to blastocysts of bovine oocytes to investigate reproductive toxicologic effects. During maturation, the oocytes were exposed to the di-ortho-substituted PCB congener 2,2',4,4',5,5'-CB (PCB 153) in the three concentrations 0.84 ng/mL, 8.4 ng/mL, and 84 ng/mL or to the non-ortho-substituted PCB congener 3,3'4,4',5-CB (PCB 126) in the three concentrations 1.006 pg/mL, 10.06 pg/mL, and 100.6 pg/mL and compared with control groups. PCB 153 had no effect on maturation but resulted in a reduced proportion of oocytes that cleaved at the highest concentration. There were no differences in blastocyst development among groups. PCB 126 resulted in a reduction in maturation percentage at the highest concentration and in blastocyst development at all concentrations. These results demonstrated adverse effects of PCB congeners on bovine oocytes and showed that this system can be used to evaluate toxic effects on oocytes and preimplantation-stage embryos.

Organochlorine pesticides in human milk from different areas of Kenya 1983-1985

Residue levels of the chlorinated hydrocarbons p,p'-DDT (2,2-bis(p-chlorophenyl)-1,1,1-trichloroethane), p,p'-DDE (2,2-bis(p-chlorophenyl)-1,1-dichloroethane), hexachlorobenzene (HCB), alpha-, beta-, and gamma-hexachlorocyclohexane (HCH), aldrin, dieldrin, and polychlorinated biphenyls (PCBs) were determined in human milk of Kenyan mothers living in different areas of Kenya. The main organochlorine contaminants found in all the milk samples analyzed were p,p'-DDT and p,p'-DDE. Great regional differences were found, and mean levels of sum DDT and DDT/DDE ratio ranged from 1.1 to 18.7 mg/kg milk fat and from 0.7 to 5.7, respectively. In general, relatively low residue levels of HCB, alpha-HCH, beta-HCH, aldrin, and dieldrin were detected in 59, 37, 27, 37, and 19%, respectively, of all the milk samples analyzed. Quantifiable residue levels of PCBs and alpha-HCH were not found. The results were examined in relation to differences in living conditions with regard to agricultural activities, dietary habits, and reported use of pesticides in the various sampling areas.

Use of malathion against ectoparasites on lactating cows

The clinical effect, residues in milk and toxicological properties of a non-commercial formulation of malathion used as an ectoparasitic agent on cattle were investigated. The results show that the malathion preparation has a desired clinical effect. The maximum concentration of malathion in milk after topical application of 5 g malathion was 0.054 μg/ml 4–6 h post-treatment, and declined to 0.005 and 0.002 μg/ml 24 and 48 h post-treatment, respectively. Totally 0.006–0.03 % of the applied dose was excreted in the milk. No toxic effect, measured as inhibition of the cholinesterases in erythrocytes and plasma, could be detected after therapeutic use of malathion.

The pharmacokinetic evaluation after 2.5 g intravenous administration of malathion, indicated that the kinetics could probably be described by a multicompartment model.