Toxicology component of fda s action plan for acrylamide
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Toxicology Component of FDA’s Action Plan for Acrylamide. Richard Canady, PhD DABT US Food and Drug Administration Center for Food Safety and Applied Nutrition www.cfsan.fda.gov. Food Advisory Sub-Committee Meeting December 4 and 5, 2002. Goal of the toxicity component of FDA’s action plan.

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Toxicology Component of FDA’s Action Plan for Acrylamide

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Toxicology component of fda s action plan for acrylamide

Toxicology Component of FDA’s Action Plan for Acrylamide

Richard Canady, PhD DABT

US Food and Drug Administration

Center for Food Safety and Applied Nutrition

www.cfsan.fda.gov

Food Advisory Sub-Committee Meeting

December 4 and 5, 2002


Goal of the toxicity component of fda s action plan

Goal of the toxicity component of FDA’s action plan

Examine the likelihood that

adverse health effects are

caused by exposure to

acrylamide-containing foods.


Context for toxicology research

Context for toxicology research

  • Ongoing assessment of knowledge base for acrylamide

    • Past assessments for

      • Food contact materials, cosmetics, water treatment, pesticide inert ingredient, specialized grout, monomer/polymer manufacture, coal mining, cigarette smoke

  • Knowledge has changed with regard to

    • How we are exposed

      • Ingestion from food, not just water

    • The levels to which we are exposed


Data gap evaluations

Data gap evaluations

  • World Health Organization/ Food and Agriculture Organization (WHO/FAO) consultation in June

  • Interagency meeting in September

  • Joint Institute for Food Safety and Applied Nutrition (JIFSAN) workshop in October

  • Expert panel at Emerging Neurotoxicology Conference in November

  • Workshop for germ cell mutagen risk assessment Spring 2003


Outline of presentation of what we know need and are planning

Outline of presentation of what we know, need, and are planning

  • Toxicokinetics

  • Animal carcinogen

  • Human neurotoxicant

  • Reproductive/developmental effects

  • Safety/risk assessment


1 what we know for toxicokinetics

1. What we know for toxicokinetics

  • Absorbed orally

    • Degree of absorption from food has not been studied

    • Most toxicity information from drinking water or injections

  • Wide and uniform distribution (oral exposure, high dose)

  • Metabolism understood for >1000 micrograms per kilogram of body weight (mcg/kg) doses

    • Saturable (CYP2E1) conversion to glycidamide

    • Glutathione conjugation

  • Elimination occurs in hours to days

    • But protein binding (-SH) and potential for cumulative damage

  • Exposure duration affects neurotoxic dose


1 toxicokinetics data needs

1. Toxicokinetics data needs

  • Bioavailability of acrylamide from food

  • Dose-response for toxicity, disposition, and binding

    • Dose metrics, critical events, mode of action

  • DNA to hemoglobin adduct relationship

  • DNA and protein binding as a marker of toxicity and risk

    • Significant nuclear protiens

  • Toxicokinetics of acrylamide in humans

  • Risk factors for susceptibility


1 plans for toxicokinetics data development

1. Plans for Toxicokinetics data development

  • FDA – National Center for Toxicological Research (NCTR)

    • DNA/protein adduct characterization and their relationship to effects and relevant external dose levels

    • Bioavailability

  • CDC – National Center for Environmental Health (NCEH)

    • Biomarker-intake relationship in studies prior to NHANES

  • Acrylamide monomer industry

    • Human dosing study, PbPk model development


2 what we know for cancer

2. What we know for cancer

  • 2-year rat studies show cancer

    • Drinking water exposures, high doses

  • Epidemiology not sufficient to change conclusions or weight of evidence


2 carcinogenicity data needs

2. Carcinogenicity data needs

  • Cancer epidemiology in populations of known high exposure

  • Chronic toxicity/carcinogenicity study

    • Acrylamide and glycidamide in rat and mouse

  • Review histology slides from existing bioassays using updated diagnostic criteria

  • Investigate the mechanism of thyroid tumor induction as reported in existing bioassays


2 fda carcinogenicity study plans intermediate to long term

2. FDA carcinogenicity study plans:intermediate to long term

  • FDA nominated acrylamide and glycidamide to the National Toxicology Program as priority selections

    • Chronic carcinogenicity and mechanism

    • NCTR will conduct these studies

    • FDA will participate in all experimental protocol designs to assure regulatory needs are met


2 fda carcinogenicity study plans shorter term

2 . FDA carcinogenicity study plansshorter term

  • Mechanistic studies, including bioavailability and markers of exposure and effect

  • DNA and protein adducts caused by acrylamide

    • Adducts are reaction products between a chemical and either DNA or proteins

    • Adducts can tell us

      • How much exposure occurs and

      • Help us understand the toxicology

    • Adducts may be particularly useful in relating animal toxicity studies to potential risks for humans from acrylamide


3 neurotoxicity

3. Neurotoxicity

  • High dose exposures in occupational settings causes neurotoxicity in humans

  • Effect widely studied, multiple species

  • Cumulative dose important

  • Age-related effects

    • One study showed more rapid onset of neurotoxicity in young vs old animals

    • Another showed greater response for neurotransmitter effects in younger animals

    • But very little data overall


3 neurotoxicity data needs

3. Neurotoxicity data needs

  • Further evaluation of interaction between dose and duration

  • Improve weight-of-evidence for or against neurodevelopmental effects at food-acrylamide doses

    • Establish a NOAEL for relevant endpoints


3 plans for neurotoxicity study

3. Plans for neurotoxicity study

  • FDA – plans are being developed for

    • Inclusion of neurotoxicity endpoints in NTP study

    • Study of neurodevelopment

  • Ongoing academic research into mechanism of neurotoxicity


4 reproductive developmental effects other than neurotoxicity

4. Reproductive/ developmental effects (other than neurotoxicity)

  • Decreased body weight, but no structural malformations

  • Reduced litter sizes (5000 mcg/kg treatment of males)

  • Germ cell mutagen in animals at high, injected doses

  • Genetic effects in mice (injection >40,000 mcg/kg)

    • Specific-locus mutations

    • Heritable or reciprocal transformations

    • Unscheduled DNA synthesis in spermatids,chromosomal aberrations or micronuclei frequency in spermatogenic cells


4 reproductive developmental effects data needs

4. Reproductive/ developmental effects data needs

  • Epidemiology for germ cell toxicity

  • Expression profiling for genotoxic effects on somatic and germ cells

  • Define the germ cell mutations generated

    • Dose-response

      • Low dose and multiple dose exposure effects

      • Compare food and drinking water exposures

    • Mechanistic

      • Adduct formation with DNA and significant nuclear proteins

      • Dominant lethal study in CYP2E1 knockout mice


4 plans for reproductive developmental effects study

4. Plans for Reproductive/ developmental effects study

  • FDA

    • Genotoxicity endpoints in NTP study, including initial subchronic studies (under development)

    • Workshop for germ cell mutagen risk assessment

  • NIOSH worker studies

    • NIEHS collaboration for reproductive/genotox

  • NIEHS evaluation of CYP2E1 knockout mice for dominant lethal effect

  • Expert review panel by National Toxicology Program (NTP) Center for the Evaluation of Risks to Human Reproduction (CERHR)


5 safety risk assessment usepa rfd and usfda adi

5. Safety/risk assessmentUSEPA RfD and USFDA ADI

  • EPA Reference dose and FDA Acceptable Daily Intake based on Burek et al 1980 finding of sciatic nerve degeneration (electron microscopic)

    • 90 day study in rats

    • Lowest observed effect level 1000 mcg/kg

    • No observed effect level 200 mcg/kg

      • Only 3 animals examined at EM level per dose group

    • Recovery seen at 144 days for LOAEL dose

  • 1000 fold uncertainty factor

  • Routine EPA re-evaluation of RfD underway


5 who fao safety risk assessment

5. WHO/FAO Safety/risk assessment

  • Noncancer effects judged unlikely at doses from food

  • Cancer

    • No consensus on quantification of risk

    • Carcinogenic potency characterized as

      • …similar to that of other carcinogens in food (benzo[a]pyrene and heterocyclic aromatic amines) …”

    • However,

      • “… intake levels for acrylamide are likely to be higher.”


Who fao conclusion

WHO/FAO conclusion

“major concern” for acrylamide based on relative cancer potency and uncertainty regarding

germ cell mutagenicity findings.


Safety risk assessment effective dose exposure adi

Safety/risk assessment - Effective dose, Exposure, ADI

  • Lowest neurotoxic dose in rats

    • 1000 mcg per kg body weight

    • No effect seen at200 mcg/kg

  • WHO/FAO – typical dietary intake

    • 0.3-0.8 mcg/kg body weight

  • FDA Acceptable Daily Intake for food contact decisions

    • 1000 fold uncertainty factor

    • 0.2 mcg/kg body weight


Summary

Summary

  • Acrylamide causes effects in animals and in humans at doses much higher than those we get through food

  • However, safety/risk assessment indicates the need for further analysis of the risk

  • There are substantial gaps in our knowledge of whether the acrylamide levels in food are likely to cause health effects

  • Data gap analyses by leading experts in a variety of venues in the last 7 months indicate what kind of information is needed

  • We have initiated programs to carry out the needed information gathering and research, and are already seeing results


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