Grit ingestion may be an important exposure route for environmental contaminants in waterfowl. Our objective was to determine turnover rate of grit in juvenile mallards (Anas platyrhynchos) by measuring the time required for juveniles to totally replace grit in the gizzard. To demonstrate the relevance of turnover rate for assessing contaminant exposure, we evaluated the suitability of wetlands receiving oil-sand effluent generated by the mining industry, as viable habitat for waterfowl. Captive mallards were allowed free access to pools of colored grit, the grit color was changed and the time required for color 1 to be replaced by color 2 determined. An exponential relationship between percent grit turnover and time was fitted to the data to obtain a grit turnover rate, k = 0.02/hr. This rate was used to determine amount of contaminants that would be ingested over 21 days by juvenile mallards using oil-sand wetlands as habitat. We demonstrate that grit ingestion could be a significant route of contaminant exposure, specifically for oil-sand related compounds such as oil and grease and naphthenic acids, to waterfowl.