Kozue Yaginuma-Sakurai

Intervention study on cardiac autonomic nervous effects of methylmercury from seafood.

To scrutinize whether the provisional tolerable weekly intake (PTWI, 3.4 microg/kg body weight/week) of methylmercury in Japan is safe for adults, we conducted an intervention study using heart rate variability (HRV) that has been considered to reflect cardiac events. Fifty-four healthy volunteers were recruited and divided into experimental and control groups. The experimental group was exposed to methylmercury at the PTWI level through consumption of bigeye tuna and swordfish for 14 weeks, and HRV parameters were compared between the two groups. In the experimental group, mean hair mercury levels, determined before and after the dietary methylmercury exposure and after 15-week wash-out period following the cessation of exposure, were 2.30, 8.76 and 4.90 microg/g, respectively. The sympathovagal balance index of HRV was significantly elevated after the exposure, and decreased to the baseline level at the end of this study. Still, such changes in HRV parameters were not found in the control group with a mean hair mercury level of around 2.1 microg/g. In conclusion, the PTWI does not appear to be safe for adult health, because methylmercury exposure from fish consumption induced a temporary sympathodominant state. Rather, long-term exposure to methylmercury may pose a potential risk for cardiac events involving sympathovagal imbalance among fish-consuming populations.

Assessment of exposure to methylmercury in pregnant Japanese women by FFQ.

OBJECTIVE To examine whether an FFQ can be used for assessing exposure to methylmercury (MeHg) by estimating MeHg intake from seafood consumption using the FFQ and confirming the accuracy of the estimated value. DESIGN Seafood consumption of pregnant women was assessed using the FFQ. Total mercury (T-Hg) concentrations of maternal red blood cells (RBC) and hair were measured as exposure indices of MeHg. SETTING A prospective birth cohort study, the Tohoku Study of Child Development (TSCD), which has been ongoing since 2001. SUBJECTS The subjects were 609 pregnant Japanese women who were enrolled in the TSCD. RESULTS MeHg intake was estimated from seafood consumption determined using the FFQ and the MeHg concentrations in each type of seafood. The accuracy of the estimated value was confirmed by comparison with T-Hg in RBC and hair. Estimated MeHg intake was 42.3 microg/week, and 43.0 % of that was from large predatory fish. Compared with the Japanese tolerable weekly intake, in total 12.5 % of the subjects exceeded it. T-Hg concentrations in RBC and hair were significantly correlated with estimated MeHg intake: r = 0.325 (P < 0.0001) for RBC and r = 0.305 (P < 0.0001) for hair. CONCLUSIONS Estimated MeHg intake based on the FFQ was significantly associated with T-Hg concentrations in RBC and hair. Although the estimated value involves uncertainties, the FFQ appears to be a useful tool for assessment of exposure to MeHg.

Prenatal exposures to environmental chemicals and birth order as risk factors for child behavior problems

OBJECTIVES To assess whether polychlorinated biphenyls (PCBs), methylmercury, lead, or parental child-rearing attitudes was most crucial for maladaptive behavior problems, we examined Japanese 30-month-old children followed up from pregnancy. METHODS The Child Behavior Checklist (CBCL) was used to assess the behavior problems in 306 children. The associations of cord-blood total PCBs (ΣPCB), total mercury (THg), and lead with each CBCL subscale were examined by multivariate analyses. RESULTS The median values in cord blood of the 306 children were 48.3 (5 and 95 percentiles, 18.6-116.3) ng/g-lipid for ΣPCB, 10.2 (4.1-24.5)ng/g for THg, and 1.0 (0.5-1.7)μg/dl for lead. The internalizing score of the CBCL was significantly correlated with ΣPCB (r=0.113) in the children, though no significant correlation was seen between any CBCL score and either THg or lead. The significant correlation disappeared when conducting multiple regression analysis with possible confounders; at that time, the birth order, home environment, and maternal intelligence quotient were significantly related to the internalizing score. Three CBCL scores and ΣPCB levels were significantly higher in the first-born children than in the second-born or following children, and the partial correlation coefficient with the adjustment for all confounders except birth order was significant between the internalizing score and ΣPCB in the latter children (r=0.175). CONCLUSIONS Internalizing behavior appears to be affected by prenatal exposure to PCBs at low levels. Under lower-level exposures, however, behavior problems may be more strongly associated with parental child-rearing attitudes involved in birth order, than with such hazardous chemicals.

Applicability of food composition tables as a tool to estimate mineral and trace element intake of pre-school children in Japan: a validation study.

Because dietary intakes of some minerals (including trace elements), especially iron (Fe), are insufficient for the needs of the general Japanese population, accurate estimation of mineral intake is important. This capability is especially necessary to preserve the health of Japanese children. Therefore, the current version of food composition tables (FCT) in Japan was evaluated for validity as tools to estimate dietary intake of minerals for children. For this purpose, 24h food duplicate samples were collected from 292 pre-school children in Miyagi prefecture, Japan. From the weights of items and food codes, intakes of nine minerals were estimated taking advantage of the FCT. In parallel, amounts of minerals in each duplicate samples were instrumentally measured by ICP-AES for Ca, Cu, Fe, Mg, Mn, P and Zn, and by flame AAS for K and Na, both after wet-ashing. The distributions of the mineral amounts were essentially normal. The comparison of the FCT-based estimates (E) and instrumental measures (M) showed that the E/M ratio was close to 1 for Ca, K, Mn, P and Zn, suggesting that E may be a surrogate of M for Ca, K, Mn, P and Zn on a group basis. The ratio being larger than 1.2 for Cu, Fe, Mg and Na indicates that a risk of over-estimation exists when E is relied upon in place of M. On an individual basis, significant differences were detected for all 9 minerals suggesting that the use of E as a surrogate for M should be practiced with care for the estimation of mineral intake.

Psychomotor Ability in Children Prenatally Exposed to Methylmercury: The 18-Month Follow-Up of Tohoku Study of Child Development

Fish contain nutrients essential to the developing fetal brain, but they are contaminated with methylmercury. The Tohoku Study of Child Development, now underway in the Sanriku coastal area of Miyagi prefecture, Japan, follows mother-child pairs to examine the risks and benefits of fish consumption during pregnancy, especially the effects of prenatal exposures to methylmercury, selenium, and docosahexaenoic acid (DHA) on child neurodevelopment. Children aged 18 months were administered the Bayley Scales of Infant Development second edition (BSID-II) and Kyoto Scale of Psychological Development (KSPD) in 2004-2008. Complete data of cord-blood total mercury (THg), cord-plasma selenium, maternal-plasma DHA, the above test scores, and confounders for 566 mother-child pairs were available. The median cord-blood THg level was 15.7 (range, 2.7-96.1) ng/g. Since the BSID-II and KSPD scores were significantly lower in the 285 boys than in the 281 girls, analyses were conducted separately. The Psychomotor Development Index (PDI) of BSID-II was significantly correlated with cord-blood THg only in the boys, and significance of the association remained unchanged after adjusting for possible confounders; i.e., a 10-fold increase in cord-blood THg was associated with a 8.3-point decrease in the score of the PDI. Other significant correlations of THg were not seen in the boys or girls. Selenium and DHA showed no significant correlations with the BSID-II or KSPD scores in either sex. In conclusion, intrauterine methylmercury exposure may affect psychomotor development, and boys appear to be more vulnerable to the exposure than girls.

Nutrient intake by kindergarten children in Beijing and Xian, China in 2004-2005, with special reference to sources of high sodium intake

Background and objectives: China has been experiencing dramatic social changes in recent years. From nutritional view, nutrient intakes of children should be clarified as baseline data at the early stage of the change. Food intake records were available to this study group for this purpose. Methods: In practice, 120 children (60 boys and 60 girls) were studied, who were at the ages of 5 to 6 years attending kindergartens in Beijing (in 2004 and 2005) and Xian (in 2005). Guardians provided informed consents on behalf of children and submitted 24-hour duplicates of foods and drinks at the amounts served to children. Results: Children took 1373 kcal energy, 59.6 g protein, 39.8 g lipid and 204.2 g carbohydrate per day. Cereals accounted for 39.1% of energy and 23.3% of protein. When compared with nationally set AI (adequate intake) or RNI (recommended nutrient intake), energy and macro-nutrient intakes were barely sufficient. Vitamin A and vitamin C intakes were quite sufficient, whereas thiamin intake was only barely so. Intake of Na was as high as more than twice AI. The Na intake was confirmed also by instrumental analysis. A close association of high Na intake with wheat-based foods was detected. Consumption of fast foods was quite limited. Conclusions: Intakes were adequate for energy and macro-nutrients already early in this century, but improvements were necessary for several micro-nutrients. Na intake was especially quite in excess; an association with wheat-based foods was detected. Food contamination with Cd or Pb was not detectable.