Evidence-based dose-response assessment for thyroid tumorigenesis from acrylamide

Area of Science:

• Toxicology
• Carcinogenesis
• Risk Assessment

Background:

• Acrylamide is a food contaminant linked to tumor development in animal studies.
• Concerns exist regarding acrylamide's DNA toxicity and mechanisms of tumor formation.

Purpose of the Study:

• To review and evaluate studies on acrylamide's DNA toxicity and tumor formation.
• To assess the modes of action for acrylamide-induced tumors, particularly in the thyroid.
• To derive health-protective dose-response values for risk assessment.

Main Methods:

• Review of existing scientific literature on acrylamide.
• Analysis of DNA toxicity and tumor formation data, distinguishing between acrylamide and its metabolite glycidamide.
• Application of the probit model, following US EPA guidelines, to analyze dose-response relationships.
• Calculation of cancer slope factor (SF) and Reference Dose (RfD).

Main Results:

• Glycidamide, a metabolite, is mutagenic, while acrylamide is not.
• Thyroid tumors are consistently observed in rats exposed to acrylamide.
• Evidence suggests both mutagenic and growth-stimulating modes of action contribute to tumor formation.
• The probit model effectively captures the dual modes of action.

Conclusions:

• Acrylamide's carcinogenic effects in rats involve both mutagenicity and thyroid growth stimulation.
• A linear cancer slope factor (SF) of 0.030 (mg/kg-day)(-1) is identified for low-dose mutagenicity.
• A Reference Dose (RfD) of 0.05-0.02 mg/kg-day is established for high-dose growth stimulation, aiding risk assessment.