Recommended Dietary Allowances (RDAs) are allocated to each food article as published in the Denmark Budget Methods in the Codex Alimentalius of the WHO/FAO Joint Committee when standards of pollutants in food are needed. When daily intakes of Food Additives and Contaminants need to be calculated, the Theoretical Maximum Daily Intake. (TMDI) and the Estimated Maximum Daily Intake (EMDI) have been generally used. TMDI and EMDI are calculated using the formulae shown below: [formula: see text] i: food article (i = 1, ....., n) A: standard value for food additives and contaminants X: mean weight of food article consumed daily l: rate of residue after cooking Exposure assessment should be more exact in order to meet social health needs and to help avoid unnecessarily strict regulations. The U. S. Food and Drug Administration (FDA) is continually improving its estimates of the dietary intakes of pesticides and essential minerals, and comparing these intakes with established safe or recommended dietary intake levels. Dietary survey methods have also improved in parallel, with examples being the USDA's Household Food Consumption Survey (1955 and 1965) and National Health and Nutrition Examination Survey II (1976-1980). In Japan, TMDI and EMDI have received more attention as methods of estimating the daily intakes of food additives and contaminants than has the Total Diet Study, even though the former are not as exact as the latter. The Japanese National Nutrition Survey is one of the most respected nutrition surveys in the world, because it has continued nationwide yearly since 1946. Nevertheless, it is very unfortunate that no one utilizes the Household Food Consumption Survey data for the estimation of intakes of food additives and contaminants, because that is not the primary purpose of the Japanese National Nutrition Survey. Practically, there are neither foods which have an uniform of food additives and contaminants nor individuals who consume uniform amounts of each food item. In this report the authors propose a revised estimation method for the daily intake of food contaminants and additives, based on food consumption data of 159 female volunteers, without using the National Nutrition Survey data. The results obtained are as follows: 1) This method succeeded in making clear the intakes of food additives and contaminants. Mean, maximum and minimum values and distribution curves for the target population were obtained. 2) The suggested name for this method is "Estimated Ecological Daily Intake (EEDI)", which is processed in terms of the food consumption structure for calculation, and methodologically estimated by food ecology.
On April 26, 1986, the fourth reactor of the Chernobyl Nuclear Power Station, in the Ukraine, of the former Soviet Union, exploded. Since March in 1991, a group including the author has been performed medical surveys and provided assistance centered mainly in Gomel district of the Republic of Belarus, which contains many severely contaminated areas due to fallout. Ultra sound scanning was performed by the Shinshu University School of Medicine Second Department of surgery on thyroid glands of children in Chechersk region, of Gomel. Twenty-one persons, each with tuberculous echogenic dots in their thyroid glands, were brought to Japan for further examination. The 137Cs residue was measured in these 21 persons, using a whole-body counter (WBC). Subsequently 137Cs was also measured in a range of food items found in the city in which they live. These studies indicate that, although the children live in the same area, differences in life style and in food intake are reflected in the amount of cesium residue in their bodies.
Recent interest concerning methylmercury that accumulates in the aquatic food chain appears to be directed not to the adverse effects of high-dose exposure in humans, but to the critical concentration at which methylmercury may affect the progeny of the exposed population. In epidemiological studies, however, uncertainties and limitations in estimating exposure make it difficult to quantify dose-response associations and can thereby lead to inaccuracies when deriving such concentrations. In this respect, benchmark dose calculation for quantitative outcomes may shed new light on the epidemiological procedure for estimating the critical concentration. After the epidemic outbreaks of methylmercury poisoning in Japan and Iraq, large-scale follow-up studies were carried out in the Faroe Islands, Seychelles and New Zealand, to clarify the effects of prenatal methylmercury exposure on child neurodevelopment in the latter half of the 1980s. This article presents an overview of the outcomes obtained from the Faroe Islands Prospective Study, as well as a brief interpretation of the benchmark dose calculation. Although the Faroe and Seychelles Islands studies did not seem to differ greatly in the study setting, such as the exposure level and sample size, the former study observed some significant dose-effect relationships between methylmercury concentrations at birth and neurobehavioral end-points, but the latter failed to find any significant associations except in one test. The discrepancy between the two conclusions is also discussed.
A workshop on the Scientific Issues Relevant to Assessment of Health Effects from Exposure to Methylmercury was held in Raleigh, North Carolina, November 18-20, 1998. At that time, most discussions focused on two of the major epidemiologic studies, e.g., Seychelles child development study and Faroese birth cohort study, associating methylmercury exposure with an array of developmental measures in children. These two studies seemed to provide different conclusions on the potential health effects of methylmercury and significant uncertainties remained because of issues related to exposure, neurobehavioral endpoints, confounders and statistics, and design. Since then, each group researching the Seychellois or Faroes cohort has reported some new findings on the risk assessment of methylmercury. This article is intended to present an overview of the above research, as well as benchmark dose calculations. One implication is that neuropsychological measures may depend on social and cultural factors including race and language, and another is that a key to resolve whether the exposure has harmed the fetus appears to lie in neurophysiological measures such as brainstem auditory evoked potentials and electrocardiographic R-R interval variability. In addition, it is likely that the findings published tend to underestimate the neurotoxic effects of developmental methylmercury exposure. In light of the precautionary principle, a conclusion on health effects of low-level dietary exposures to methylmercury needs to be drawn from all available data including the New Zealand study.