Estimation of dietary intake of cadmium: reliability of methods

The reliability of intake studies depends on representative sampling of foods, quality assurance of analytical methods, selection of adequate food consumption data and combining concentrations of heavy metals in foods with food consumption figures. The food balance sheet is usually unsuitable for intake estimations of cadmium, since it covers mainly unprocessed food and does not include individual food consumption data. The reliability of household surveys could be improved by taking food wastage into account, more detailed description of meals eaten outside the home, and calculating per capita consumption figures. The duplicate portions method seems to be the most reliable of the available techniques, but does not provide realistic information on variations in long-term intake, for which dietary surveys, food recall studies or food frequency questionnaires should be used. The duplicate portions technique is suitable for studies of risk groups. The average intake of cadmium in Finland is about 10 micrograms per day, but 5-10% of the population ingests more than 20 micrograms of cadmium per day. Additional exposure from smoking, ambient air and drinking-water considerably increases the variation in exposure.