Yoshiko Imai

Background exposure of general population to cadmium and lead in Tainan city, Taiwan

Venous blood samples, 24-h total food duplicate samples, and rice samples were collected from 52 adult nonsmoking women in the city of Tainan, southern Taiwan, in 1994, and analyzed for cadmium (Cd) and lead (Pb) by wetdigestion followed by graphite furnace atomic absorption spectrophotometry. Daily dietary intake was 10 μg for Cd and 22 μg for Pb as geometric means, of which Cd and Pb in rice accounted for 34% and 1.4% of daily Cd and Pb intakes, respectively. The counterpart values for blood were 1.11 ng/ml and 44.5 ng/ml for Cd and Pb, respectively. International comparison with recently published data suggests that the exposure to Cd in Tainan should be among the lowest in the world.

Reduced cadmium and lead burden in Japan in the past 10 years

Objective To investigate the current levels of exposure of the Japanese population to cadmium and lead, in comparison with the levels in 1980s. · Design A nation wide survey was conducted in 1991–1994 (the 1990 study) in 19 study sites in Japan as a follow-up to a study conducted in 1979–1983 (the 1980 study). Blood samples and 24-h total food duplicates were collected from women who did not smoke or drink habitually. Methods Blood and food duplicates (after homogenization) were analysed for cadmium (Cd-B and Cd-F, respectively) and lead (Pb-B and Pb-F) by graphite furnace atomic absorption after wet-ashing. · Results Altogether, 467 women volunteered for blood sampling. Of these women, 375 also gave food duplicates. Geometric mean (GM) Cd-B levels in the 1990 study were lower than the corresponding 1980 values in most study sites so that the 1990 grand GM (1.98 ng/ml) for Cd-B was significantly lower than the 1980 GM (3.58 ng/ml). This reduction in Cd-B was related to the reduction in Cd-F (GM for Cd-F was 38.0 μg/day in the 1980 study and 30.0 Etg/day in the 1990 study). Dietary intake was almost exclusively the route of Cd burden among the populations studied. Both Pb-B and Pb-F also showed a remarkable reduction, i.e. from 33.9 ng/ml (1980 GM) to 23.2 ng/ml (1990 GM) in the case of Pb-B, and from 32.2 μg/day (1980 GM) to 7.1 μg/day (1990 GM) in the case of Pb-F. Pb-B, however, did not correlate with Pb-F either in the 1980 or the 1990 study, because Pb intake via inhalation of air remained significant when compared with dietary intake. · Conclusion The Cd burden in Japan has decreased markedly in the past 10 years, although it is still higher than in other countries. The Pb burden has been quite low.

Occupational exposure to solvent mixtures: effects on health and metabolism

Exposure monitoring by personal diffusive samplers, biological monitoring of toluene exposure by urinary hippuric acid determination, haematology, serum biochemistry for liver function, and a subjective symptom survey by questionnaire were conducted on 303 male solvent workers. They were exposed to a mixture of solvents including toluene (geometric mean 18 ppm), methyl ethyl ketone (MEK; 16 ppm), isopropyl alcohol (IPA; 7 ppm), and ethyl acetate (9 ppm). The intensity was mostly below unity using the additiveness formula based on current Japanese occupational exposure limits, but more than eight times unity at the maximum. The results were compared with the findings in 135 non-exposed male workers of similar ages. Haematology and liver function tests did not show any exposure related abnormality, and subjective symptoms were mostly related to central nervous system depression and local irritation. Further analysis suggested that the irritation effects were not related to exposure to MEK. Analysis of the relation between toluene exposure and hippuric acid excretion in urine showed that there was no metabolic interaction between MEK and toluene, or between IPA and toluene. Overall, therefore, it is concluded that there was no sign or symptom detected to suggest anything other than toluene toxicity, that there was no evidence to indicate any modification of toluene toxicity or metabolism due to coexposure, and that the additiveness assumption is reasonable for risk assessment for the combination of solvents under these exposure conditions.

A Comparison of the Food Composition Table-based Estimates of Dietary Element Intake with the Values Obtained by Inductively Coupled Plasma Atomic Emission Spectrometry: An Experience in a Japanese Population

In order to make quantitative comparison between food composition table-based estimates and instrumental measures by inductively coupled plasma atomic emission spectrometry (ICP-AES), total food duplicates were collected from 232 adult women in 10 study regions in 9 Prefectures in Japan. Daily dietary intake of 5 elements, sodium (Na), potassium (K), phosphorus (P), calcium (Ca) and iron (Fe), were estimated from the weights of food items in each duplicate by use of food composition tables. Parallel to this the intakes were measured by wet-ashing of food duplicate homogenates followed by ICP-AES analysis. Because the emission intensity of K was significantly modified by Na co-present at various concentrations, K was measured after Na concentration was reduced to the value 150 mg/L by dilution. The comparison of the two sets of the results, the estimated values and the measured values, showed that the estimated values were significantly larger than the measured values in the cases of Na, K, Ca and P (the ratio of the estimated to the measured values: 118% for Na, 115% for K, 109% for Ca; and 130% for Fe), whereas the two values essentially agreed with each other in the case of P (ratio: 93%). The differences were too large for any nutritional evaluation to be made when the method of Bland and Altman is applied. The significance of the differences in relation to nutritional evaluation of element intake is discussed.

Insufficient Calcium and Iron Intakes among General Female Population in Japan, with Special Reference to Inter-Regional Differences

Dietary intakes of calcium (Ca) and iron (Fe) were investigated in 227 women (mostly housewives) in 12 regions in Japan in 1991-1993 by the 24-hour food duplicate method. Nine regions out of 12 had been previously studied in 1977-1982. Utilizing Standard Food Composition database, mean Ca and Fe-intakes in 1991-1993 were estimated to be 602 and 10.4 mg/day, respectively; the former was barely sufficient and the latter was below sufficiency when compared with the Recommended Daily Allowance in Japan for pre-menopausal women. Ca- and Fe-intake did not increase in the 10-year period. Further analysis after classification of the women into three groups of farmers in Okinawa, farmers in Mainland Japan and urban residents showed that Ca and Fe insufficiency was most evident among Okinawa farmers. The leading Ca sources were milk, pulse, vegetables and fish-shellfish, but consumption of milk was generally low, especially among Okinawa farmers. Pulse, vegetables and fish-shellfish were 3 major Fe sources; Okinawa farmers depended more on vegetables and less on fish-shellfish.