Cadmium occurs naturally in the environment in its inorganic form, and anthropogenic sources have further contributed to background levels of cadmium in soil, water and living organisms. The general population is exposed to cadmium from multiple sources, including smoking, but in the non-smoking general population food is the dominant source. Cadmium is primarily toxic to the kidney, but can also cause bone demineralisation and has been statistically associated with increased risk of cancer in the lung, endometrium, bladder, and breast.
A Provisional Tolerable Weekly Intake (PTWI) for cadmium of 7 μg/kg body weight was established by the Joint FAO/WHO Expert Committee on Food Additives (JECFA) in 1988. In 2010, the JECFA reviewed its previous evaluation and established a provisional tolerable monthly intake (PTMI) of 25 μg/kg body weight corresponding to a weekly intake of 5.8 μg/kg body weight. In 2009 and subsequently confirmed in 2011, the Panel on Contaminants in the Food Chain issued an opinion in which they recommended that the PTWI should be reduced to a tolerable weekly intake (TWI) of 2.5 μg/kg body weight in order to ensure a high level of protection of all consumers, including exposed and vulnerable subgroups of the population.
A number of studies have investigated cadmium levels in a range of foods. In light of the recommended lowering of the health based guidance value, it was considered important to better identify major dietary sources by reviewing cadmium levels in food on the European market and estimate cadmium exposure using detailed individual data from the EFSA Comprehensive European Food Consumption Database.
In about half of the food samples available to EFSA cadmium was not detected or levels were below the limit of quantification, Individual quantified values ranged from a low of 0.001 μg/kg for drinking water to a high of 61,000 μg/kg for horse kidney. Tap water had the lowest average cadmium levels while algal supplements and seaweeds used as a vegetable had the highest average cadmium levels. Thirteen out of 144 food categories had a middle bound mean above 100 μg/kg including algal formulations, cocoa powder, bitter and bitter-sweet chocolate, crustaceans, edible offal, fish and seafood not specified beyond FoodEx Level 1, frogs’ legs, cultivated fungi, wild fungi, oilseeds, seaweeds and water molluscs.
By using the more detailed and refined food consumption information now available through the EFSA Comprehensive European Food Consumption Database and weighting results from the different age groups in the survey population according to the number of years they include, average middle bound lifetime cadmium dietary exposure for the European population as a whole was estimated at 2.04 μg/kg body weight per week. It was highest in toddlers with an average of 4.85 μg/kg body weight per week and lowest in the elderly population group at 1.56 μg/kg body weight per week. Potential 95th percentile middle bound lifetime exposure, with the assumption that the same individuals retained high exposure throughout life, was estimated at 3.66 μg/kg body weight per week with a high of 8.19 μg/kg body weight per week for toddlers and a low of 2.82 μg/kg body weight per week for the elderly. Individual dietary survey results varied between a minimum lower bound mean of 1.15 and a maximum upper bound of 7.84 μg/kg body weight per week and a minimum 95th percentile lower bound of 2.01 and a maximum upper bound of 12.1 μg/kg body weight per week reflecting different dietary habits but also likely differences in survey methodologies and the countries covered for the different age classes.
Often it is not the food with the highest cadmium levels, but foods that are consumed in larger quantities that have the greatest impact on cadmium dietary exposure. This was true as the broad food categories of grains and grain products (26.9%), vegetables and vegetable products (16.0%) and starchy roots and tubers (13.2%) were identified as major contributors. Looking at the food categories in more detail, potatoes (13.2%), bread and rolls (11.7%), fine bakery wares (5.1%), chocolate products (4.3%), leafy vegetables (3.9%) and water molluscs (3.2%) contributed the most to cadmium dietary exposure across age groups. At the finest level of detail given for the food consumption information, wheat bread and rolls (6.4%), boiled potatoes (5.7%), pastries and cakes (4.0%), potatoes without preparation specified (3.1%), rice (3.0%) and carrots (2.2%) were important contributors.
Both the Chemicals Branch in the Division of Technology, Industry and Economics of the United Nations Environment Programme and the EFSA Panel on Contaminants in the Food Chain have expressed concern that the margin between the average weekly intake of cadmium from food by the general population and the health-based guidance values is small. The EFSA Panel concluded that although adverse effects are unlikely to occur in an individual with current dietary exposure, there is a need to reduce exposure to cadmium at the population level because of the limited safety margin.
The current review confirmed that children on average and adults at the 95th percentile dietary exposure could exceed health-based guidance values.