Poster Topical Area: Policy
Location: Hall D
Poster Board Number: 853
Objectives: The Food and Nutrition Board of the Institute of Medicine (FNB) establishes Tolerable Upper Intake Levels (UL) for nutrients, defined as “the highest level of daily nutrient intake that is likely to pose no risk of adverse health effects to almost all individuals in the general population”. The Environmental Protection Agency (EPA) establishes oral reference doses (RfD) for chemicals in the environment, defined as “an estimate with uncertainty spanning perhaps an order of magnitude of a daily oral exposure to the human population including sensitive subgroups that is likely to be without an appreciable risk of deleterious effects during a lifetime”. The objectives of this study are (1) compare ULs with RfDs for elements, (2) examine the basis for the levels, and (3) determine if results support establishing a uniform approach to setting safe levels for elements in food and the environment.
Methods: Current ULs and RfDs for male adults were obtained from the National Institutes of Health - Office of Dietary Supplements and EPA websites, respectively. ULs were compared with RfDs. A ratio was developed to calculate differences in values. For each element, selection of (1) studies relied upon, (2) critical adverse health effect, (3) no observable adverse effect level (NOAEL) or lowest observable adverse effect level (LOAEL), and (4) uncertainty factor (UF) used for each UL and RfD were evaluated to assess differences in levels.
Results: The difference in UL/RfD ratios ranged from 0.7 to 5.7. The largest differences were seen with copper, fluoride, molybdenum, and vanadium. The bases for the differences were selection of studies, critical adverse health effects, selection NOAELs or LOAELs, and UFs.
Conclusions: The FNB and EPA rely on similar methodologies to set “safe” levels for intake of elements. Both select relevant studies, derive a NOAEL or LOAEL, and divide the level by an UF to account for uncertainties (e.g., extrapolation from animals to humans and susceptibility to adverse effects). Although the intent of ULs and RfDs is to use the weight of the evidence to define a safe upper limit of exposure, different results were obtained for certain elements. It may be prudent for agencies to harmonize the setting of safe levels of nutrients for exposure via the diet and environment.
Tufts University - Friedman School of Nutrition Science and Policy
Ladera Ranch, California