3-MCPD and glycidol and their esters

Transcription

1 Toxicological Risk Assessment of 3-monochloropropane-1,2-diol (3-MCPD) Esters and Glycidol Esters: Is there a Need for Concern? Ivonne M.C.M. Rietjens Division of Toxicology Wageningen University ivonne.rietjens@wur.nl 3-MCPD and glycidol and their esters fatty acid esters: mono- and di-esters Especially 3-MCPD and glycidol esters: * Food process contaminants * Widespread in refined vegetable oils and fats Risk assessment: Risk assessment as defined by the FAO and WHO Define: Hazard = an agent or condition, with the potential to cause an adverse health effect Risk = the probability that an adverse health effect will occur Risk = Hazard + Exposure Risk assessment: the process by which hazard, exposure and risk are determined Risk assessment: 3-MCPD & 3-MCPD esters: Hazard assessment: Critical effect 3-MCPD: renal tubular hyperplasia Tolerable daily intake (TDI) 3-MCPD: 2 mg/kg bw/day Exposure assessment: Estimated daily intake (EDI) : BfR 2007/2009: 3-MCPD in refined vegetable fats: Adult (60 kg): 100 g vegetable fat (80% fat content) assuming 100% hydrolysis 3-MCPD esters to 3-MCPD with maximum level of 7.4 mg 3-MCPD/kg fat: EDI is about 10 mg/kg bw/day = 5 times the TDI with median level of 3.1 mg 3-MCPD/kg fat: EDI is about 4 mg/kg bw/day = 2 times the TDI Risk assessment: 3-MCPD & 3-MCPD esters: Exposure exceeds TDI: risk management options 1) Reduce exposure by lowering residual levels of 3-MCPD esters in final products 2) Demonstrate/investigate that not all 3-MCPD esters are fully hydrolysed to result in 3-MCPD 3) Reconsider hazard assessment: is TDI still adequate given recent new toxicity data: toxicology of 3-MCPD and 3-MCPD esters 1

2 Toxicology 3-MCPD & 3-MCPD esters 3-MCPD esters: Upon oral intake: 3-MCPD esters may be hydrolysed to 3-MCPD and free fatty acids by lipases or acid hydrolysis in the gastrointestinal tract In vitro studies: mono-esters: nearly completely hydrolysed within 1 minute di-esters: release 3-MCPD slower; 45% after 1 min, 65% after 5 min (Seefelder et al Food Add Contam 25: ) Major health concern 3-MCPD esters: release of 3-MCPD Toxicology 3-MCPD & 3-MCPD esters Major health concern: release of 3-MCPD 3-MCPD is a non-genotoxic carcinogen, causing tumours in various organs when dosed at high levels to rodents (mammary gland fibromas, Leydig cell tumours, renal tumors) kidney main target organ renal tubular hyperplasia most sensitive endpoint kidney tumors are secondary to chronic progressive nephropathy LOAEL of 1.1 mg/kg bw/day basis for TDI established by SCF and JECFA effects on male fertility: NOAEL 1 mg/kg bw/day Carcinogens: two categories: 1) Genotoxic carcinogens (glycidol): they damage DNA thereby causing mutations and eventually cancer Risk assessment: no threshold; no safe exposure level can be established Risk management: 1) ALARA; as low as reasonably achievable 2) Margin of Exposure MOE = BMDL 10 /EDI: should be above to conclude there is a low priority for risk management Carcinogens: two categories 2) Non-genotoxic carcinogens (3-MCPD): they cause tumors by another mechanism for which a threshold can be established Risk assessment: threshold; safe exposure level can be established For contaminants, like 3-MCPD, this safe exposure level is the so-called: Tolerable Daily Intake (TDI) = dose (in mg/kg bw/day) that can be consumed on a daily basis during a whole life time without an adverse effect Tolerable Daily Intake (TDI): How established? Tolerable Daily Intake (TDI): How established? TDI = Tolerable daily intake for unavoidable contaminants like 3-MCPD = NOAEL x 1/10 x 1/10 x other Uncertainty Factors (UFs) interspecies intraspecies quality of data type of exposure NOAEL = No Observed Adverse Effect Level LOAEL = Lowest Observed Adverse Effect level TDI is used in risk assessment 2

3 SCF 2001 (Scientific Committee on Food) TDI 2 mg 3-MCPD/kg bw/day Based on: Sunahara et al. (1993): at 1.1 mg 3-MCPD/kg bw/day some indications of adverse effects in several organs which attained statistical significance at the higher doses SCF considered this level a LOAEL (close to the NOAEL) Taking into account also other limitations in the data base (e.g. lack of reproductive/developmental toxicity studies) an overall uncertainty factor of 500 was applied JECFA 2007 (Joint FAO/WHO Expert Committee on Food Additives) TDI 2 mg 3-MCPD/kg bw/day TDI also Based on: Sunahara et al. (1993): LOAEL (not a NOAEL) 1.1 mg 3-MCPD/kg bw/day uncertainty factor of 500 to allow for: interspecies differences, human variability in response, & absence of a clear NOAEL & to account for the effects on male fertility & for inadequacies in the studies on reproductive toxicity Both SCF and JECFA: uncertainty factor of 500 To allow for: - Inter- and intraspecies differences (= default UF 100) - Extrapolating LOAEL to NOAEL - Uncertainty in data base with respect to reproductive and developmental toxicity uncertainty factor of 500 may be reduced when using BenchMark Dose approach instead of LOAEL, NOAEL approach NOAEL: Disadvantages: - NOAEL dependent on sample size more dose groups, more animals lower NOAELs; better experimental designs are penalized - NOAEL limited to experimental dose - NOAEL differs across studies - only one experimental data point is used BMR = benchmark response small increase (pe 5%) in effect over background level Advantages over NOAEL * not dependent on set-up of experiment * making use of all toxicity data BMD = Bench Mark dose dose causing the BMR BMDL = statistical lower confidence limit of the BMD * BMD approach preferred over NOAEL approach 3

4 Fraction Affected :45 01/ BMDL BMD Gamma Multi-Hit Model with 0.95 Confidence Level Gamma Multi-Hit dose Fraction Affected :41 01/ BMDL BMD Weibull Weibull Model with 0.95 Confidence Level dose Fraction Affected :42 01/ BMDL BMD Multistage Multistage Model with 0.95 Confidence Level dose 9/29/2011 Deriving health-based guidance values BMDL: same level of protection as NOAEL ratio (NOAEL/CEDL) on log-scale Histogram of 395 NOAEL/BMDL ratios (log 10 - scale) for the same dose-response data in rat and mouse (NTP) studies * The traditional uncertainty factors can be applied Toxicology of 3-MCPD Hwang et al. (2009) Regul Toxicol Pharmacol 53, : re-analysed data Cho et al. (2008) using the BMD (BenchMark Dose) approach BMDL 10 male rat incidence data for renal tubular hyperplasia: 0.87 mg/kg bw/day If used instead of NOAEL for deriving a TDI: - if default UF 100: TDI 8.7 mg/kg bw/day - no extra UF for extrapolation LOAEL to NOAEL needed but perhaps still extra UF for missing data if UF 300 (<500): TDI 2.9 mg/kg bw/day if UF 200 (<500): TDI 4.3 mg/kg bw/day Toxicology of 3-MCPD Two long term toxicity rat studies available: 1) Cho et al. (2008) Food Chem Toxicol 46, LOAEL 1.89 mg/kg bw/day for male rats for renal tubular hyperplasia Hwang et al. (2009) re-analysed these data using the BMD approach: BMDL mg/kg bw/day But also: 2) Sunahara et al. (1993), Unpublished report made available to SCF and JECFA and used for defining the TDI LOAEL 1.1 mg/kg bw/day for renal tubule hyperplasia Sunahara et al. (1993) Unpublished report Made available for BMD analysis: Dose in mg 3-MCPD/ kg bw/day gender Sum of renal neoplastic findings (tubular hyperplasia, tubular adenoma and a single oncocytoma in the lowest dose male group) (incidence/no of animals) 0 male 3/ male 7/ male 16/ male 39/50 0 female 2/ female 5/ female 20/ female 40/50 Sunahara et al. (1993) Unpublished report Results BMD analysis data for sum of neoplastic findings in the kidney of male and female Fischer rats exposed orally to 3-MCPD for 104 weeks (Sunahara et al. 1993) using BMDS version software and the default settings, but no restrictions Sunahara et al. (1993) Unpublished report Results BMD analysis male+female combined n Log likelihood reduced full p value accepted BMD 10 mg/kg bw/day BMDL 10 mg/kg bw/day Model: gamma Weibull multistage BMDL mg/kg bw/day gamma yes multistage yes weibull yes quantal linear yes Use lowest value: conclusion: BMDL 10 = 0.66 mg/kg bw/day 4

5 Toxicology of 3-MCPD Analysis of the data of Sunahara et al using the BMD (BenchMark Dose) approach BMDL 10 for the sum of neoplastic findings in the kidney of male and female Fischer rats: 0.66 mg/kg bw/day If used instead of NOAEL for deriving a TDI: - if default UF 100: TDI 6.6 mg/kg bw/day - no extra UF for extrapolation LOAEL to NOAEL needed but perhaps still extra UF for missing data if UF 300 (<500): TDI 2.2 mg/kg bw/day if UF 200 (<500): TDI 3.3 mg/kg bw/day Both SCF and JECFA: uncertainty factor of 500 to allow for: - Inter & intra species differences (default UF 100) - Extrapolating LOAEL to NOAEL - Uncertainty in data base with respect to reproductive and developmental toxicity When using BMD approach UF can be lower than 500 but may still be above 100 because of uncertainty in data base with respect to reproductive and developmental toxicity Toxicology 3-MCPD: uncertainty data base 3-MCPD was shown to inhibit male fertility in several reproductive toxicity studies Rats doses > 1 mg/kg bw/day 3-MCPD decreased sperm motility & impaired male fertility (NOAEL 1 mg/kg bw/day) Rats doses > mg/kg bw/day alteration in sperm morphology and epididymal lesions Reduced fertility males other mammalian species: hamsters, guinea pigs, dogs, rhesus monkeys although at slightly higher doses than in rats 40 years ago: 3-MCPD (alpha-chlorohydrin) was considered a potential male contraceptive Toxicology 3-MCPD: uncertainty data base JECFA: NOAEL for effects on male reproductive parameters 1 mg/kg bw/day If this is considered an adequate NOAEL for reproductive and developmental toxicity: The BMDL 10 values from the two chronic rats studies would cover these effects and an uncertainty factor of 100 could be used resulting in a TDI that would be at least 6.6 mg/kg bw/day Risk assessment: 3-MCPD & 3-MCPD esters Hazard assessment: TDI 3-MCPD: if 6.6 mg/kg bw/day Exposure assessment: Estimated daily intake (EDI) : BfR 2007/2009: 3-MCPD in refined vegetable fats: Adult (60 kg): 100 g vegetable fat (80% fat content) assuming 100% hydrolysis with maximum level identified for margarine of 7.4 mg 3- MCPD/kg fat: daily intake 3-MCPD esters to 3-MCPD: EDI is about 10 mg/kg bw/day = 1.5 times the TDI with median level of 3.1 mg 3-MCPD/kg fat: EDI is about 4 mg/kg bw/day = below the TDI Toxicology of 3-MCPD and 3-MCPD esters New study since previous evaluations: It is concluded that drinking water administration of 3-MCPD for 104 weeks revealed no evidence of carcinogenic potential species differences in toxicity 3-MCPD: is mouse or rat the best human model? 5

6 Toxicology of 3-MCPD and 3-MCPD esters New study since previous evaluations: aug day study with male & female rats (n=10 each) - 3-MCPD (29.5, 7.37, & 1.84 mg/kg bw/day) or - 3-MCPD dipalmitate (156.75, 39.19, & 9.78 mg/kg bw/day) Toxicology of 3-MCPD and 3-MCPD esters New study since previous evaluations: - Urinary 3-MCPD and 3-MCPD mercapturate; at equimolar doses: 3-MCPD dipalmitate 30% lower urinary metabolites as compared to 3-MCPD - Confirmed kidney and testes to be the critical organs - BMDL 10 values kidney and testes toxicity - 3-MCPD: 2.5 and 6.0 mg/kg bw/day - 3-MCPD dipalmitate 17.4 (3.27 mg 3-MCPD equivalents) and 44.3 mg/kg bw/day - Confirms that kidney is most sensitive endpoint and that BMDL 10 and thus TDI can be higher Toxicology of 3-MCPD: conclusions Two chronic rat studies: most sensitive endpoint: renal tubular hyperplasia LOAEL resp 1.1 and 1.87 mg/kg bw/day More recent: Jeong et al. 2010: chronic mouse study 3-MCPD no evidence of carcinogenic potential BMD analyses of chronic rat data: BMDL 10 of resp 0.66 and 0.87 mg/kg bw/day 90 day study 3-MCPD and 3-MCPD dipalmitate BMDL 10 (kidney) of resp 2.5 and 17.4 (3.27 mg 3- MCPD equivalents) /kg bw/day TDI derived from these BMDL 10 values will depend on the UF chosen, and may be higher than 2 mg/kg bw/day Toxicology of 3-MCPD esters: conclusions Future strategies to be considered: Increase knowledge on in vivo ADME (is the assumption of 100% release of 3-MCPD from 3- MCPD esters correct) Increase knowledge on species differences in toxicity 3- MCPD: is mouse or rat the best human model? Re-evaluate the TDI 3-MCPD based on re-evaluation of the rat chronic studies using the BMD approach Define TDI for 3-MCPD esters Best approach: Reduce exposure by lowering residual levels of 3-MCPD esters in final products Risk assessment of glycidol esters assuming 100% hydrolysis glycidol esters to glycidol glycidol is - A genotoxic carcinogen and - A multisite carcinogen in rodents - NTP studies in both Fischer 344 rat and B6C3F mice are available; for an overview see: Bakhiya et al. Mol. Nutr. Food Res. 55 (2011) Risk assessment based on MOE approach - MOE: Margin of Exposure (BMDL 10 /EDI): should be above to conclude there is a low priority for risk management Risk assessment of glycidol esters Based on MOE approach: - NTP: 10% tumor incidence at 4.1 mg/kg bw/day - Worst case intake estimate glycidol: Adults (60 kg): 0.33 mg/kg bw/day (75 th percentile daily intake refined fats: 20g) 1.33 mg/kg bw/day (maximum daily fat intake: 80g) MOE = and 3050 indicating low level of concern especially for adults (75 th percentile EDI) Babies fed infant formula: exposure is 6 mg/kg bw/day (6g fat/kg consumption and 1 mg glycidol/kg fat in infant formula) MOE = 670: may raise a concern Bakhiya et al. Mol. Nutr. Food Res. 55 (2011)

7 Toxicology of glycidol esters: conclusions Future strategies to be considered: Increase knowledge on in vivo ADME (is the assumption of 100% release of glycidol from glycidol esters correct) Low risk for adults but may pose a risk to babies fed infant formulas Best approach (given that glycidol is a genotoxic multisite carcinogen): Reduce exposure by lowering residual levels of glycidol esters in final products especially in infant formula 3-MCPD and glycidol and their esters Overall conclusions: There is only limited or low concern over risks associated with estimated levels of exposure to 3-MCPD or glycidol and their esters, with the exception of the levels of glycidol and its esters in infant formulas TDI for 3-MCPD needs to be reconsidered using the BMD approach and taking into account the new 90 day study Optimal future approach: lowering of the residual levels so that TDI for 3-MCPD is not exceeded and MOE for glycidol is above for all situations Acknowledgement Dr Iekje Berg Sime Darby Unimills B.V. Zwijndrecht, The Netherlands Dr Gabriele Scholz, Dr Walli Seefelder, Dr Benoit Schilter Nestlé Research Center, Lausanne, Switzerland 7