Zuo-Wen Zhang

Determination of lead and cadmium in food and blood by inductively coupled plasma mass spectrometry: a comparison with graphite furnace atomic absorption spectrometry

To compare inductively coupled plasma mass spectrometry (ICP-MS) and graphite furnace atomic absorption spectometry (GF-AAS) as the method for determining lead and cadmium in the human diet and blood, 418 diet homogenate samples and the same number of blood samples were collected from Chinese and Japanese women and were analyzed by the two methods. The results showed that our ICP-MS method is precise and accurate, being comparable to the GF-AAS method established previously. The ICP-MS method is simple and fast spending only one-tenth of the time necessary for GF-AAS and allows simultaneous analyses of lead and cadmium with low detection limits. When applied to actual sample analysis, however, ICP-MS results tend to be 10-20% lower than GF-AAS results in the analysis of lead in the diet and blood and cadmium in blood. This is possibly due to some interference in ICP-MS and matrix of samples. As the ICP-MS results could be mathematically corrected to be equivalent to the GF-AAS results, we conclude that this ICP-MS method can be used as a routine analytical method for the determination of lead and cadmium in human diet and blood samples.

Cadmium contents in rice samples from various areas in the world

Rice samples consumed by local populations were collected in 17 areas in the world, mostly from Asia, i.e. ten areas, but eight areas outside of Asia were also included during the period of 1990 to 1995. The samples amounted to 1546 in total, and were analyzed for cadmium (Cd) by electrothermal atomic absorption spectrometry. The data show that the highest and the lowest geometric means of Cd contents in rice from Asia was 55.70 and 2.67 ng/g, respectively, and 133.20 and 0.88 ng/g outside of Asia. The geometric mean Cd contents in rice from Japan was 55.70 ng/g, which is essentially similar to the levels determined in the early 1980s. We conclude that a substantial difference exists in Cd contents in rice for local consumption depending on the areas in the world, and that there is no significant changes in Cd levels in rice harvested in Japan over the past 10 years.

Lead and cadmium contents in cereals and pulses in north-eastern China

It is known that, unlike Japanese, Koreans or southern Chinese who depend on rice as a major source of energy for daily life, people in north-eastern China rely not only on rice, but on wheat and other cereals and to a lesser extent also on pulses. Cereal and pulse samples were collected from open markets in north-eastern China, and analyzed by inductively-coupled plasma spectrometry (ICP-MS) for two potentially hazardous heavy metals--lead (Pb) and cadmium (Cd). The average Pb level in cereals (31.3 ng Pb/g as a geometric mean) and that of pulses (25.7 ng Pb/g) were similar to each other with no significant difference. Among the cereals, Pb contents were higher in foxtail millet (54.3 ng/g) and lower in maize (35.4 ng Pb/g; grain and flour in combination), wheat flour (28.8 ng Pb/g) and rice flour (22.7 ng Pb/g). Lead levels in two important types of pulses, kidney bean and soybean (24.6 and 30.8 ng Pb/g, respectively), were comparable to the levels in rice and wheat. In contrast, Cd levels were substantially higher in pulses (55.7 ng Cd/g) than in cereals (9.2 ng Cd/g), and among the pulses, Cd in soybean (55.7 ng Cd/g) was significantly higher than that in kidney bean (23.8 ng Cd/g). The possible public health implication of the Pb and Cd levels, especially the high Pb level in foxtail millet (54.3 ng Pb/g) and the high Cd level in soybean (73.5 ng Cd/g), is discussed.

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.

Non-occupational exposure of adult women in Manila, the Philippines, to lead and cadmium

In total, 45 adult women in Manila, the Philippines, volunteered to participate in the study by offering peripheral blood samples and 24-h total food duplicate samples. In addition, they offered raw (uncooked) rice as well as wheat flour and maize starch from the kitchen. Lead (Pb) and cadmium (Cd) in food duplicates and blood samples were measured by inductively coupled plasma mass spectrometry after homogenization (when necessary) and wet-ashing. The consumption of rice, wheat and maize was calculated by weighing each food item in the duplicates taking advantage of the food composition tables. The dietary exposure level of the women was 11 micrograms Pb/day and 14 micrograms Cd/day, and the levels of Pb and Cd in their blood were 37 ng Pb/ml and 0.47 ng Cd/ml. There is a subtle age-dependent increase in the dietary burden of Pb and Cd and also in blood levels of Pb and Cd. Rice accounted for 18 and 21% of dietary Pb and Cd intake, respectively and cereals (i.e. rice, wheat and maize in combination) accounted for 24% both for Pb and Cd. The calculation from the published data on air quality in Manila suggested that another and yet a greater source of Pb burden was Pb in atmospheric air which may account for 85% of total Pb uptake, whereas the amount of Cd in air was quite small (i.e. < 10% of the total uptake).

Urban–rural comparison on cadmium exposure among general populations in Shandong Province, China

In 1996, peripheral blood samples and 24-h food duplicate samples together with samples of wheat, rice, foxtail millet and maize were collected from 50 non-smoking women each from Jinan (a provincial capital) and Baiquan (a nearby basically self-sustaining farming village) in China. The samples were analyzed for cadmium (Cd) contents by graphite furnace atomic absorption spectrometry after wet digestion. The dietary Cd intake of the people in the city was 6.4 micrograms/day as a geometric mean (GM) and 5.9 micrograms/day for the villagers. The Cd level in blood was 0.48 and 0.29micrograms/l (as GMs) for the city and village people, respectively. Thus, Cd burden of the people in the city tended to be greater than that for those in the village. Nevertheless, the Cd burden of the Jinan citizens was lower than the values published for people in large cities in China. When Cd intake via the four cereals was compared with Cd in total food to estimate the total contribution of the four cereals (combined) in total dietary Cd intake, the cereals accounted for 60% of total dietary Cd intake among the city people and as high as 78% among the villagers. Cadmium contents in the four cereals were in a narrow range and it was considered acceptable to combine all cereals in evaluating them as dietary Cd sources.

Non-occupational exposure of Malay women in Kuala Lumpur, Malaysia, to cadmium and lead

Abstract Peripheral blood and 24-h total food duplicate samples were obtained from 49 adult Malay women in Kuala Lumpur, Malaysia, in July, 1995. Samples of boiled and uncooked (raw) rice were also collected from the subjects. The blood samples, homogenates of each food duplicates and rice samples (both cooked and raw) were digested by heating in the presence of mineral acids, and the digests were subjected to analysis for cadmium (Cd) and lead (Pb) with a system composed of a fully automated liquid sampler, a graphiie furnace atomic absorption spectrometer and a data processor. The geometric mean metal concentrations in blood were 0.71 ng Cd per ml and 45.6 ng Pb per ml, and the dietary metal intakes were 7.31 μg Cd per day and 10.1 μg Pb per day. The metal intake via rice accounted for 53% and 13% of total dietary intake of cadmium and lead, respectively. When the absorption from the air and foods was compared, the cadmium burden came almost exclusively from foods, whereas the lead burden came both from air (44%) and foods (56%).

Contents of pollutant and nutrient elements in rice and wheat grown on the neighboring fields

Because of recent agricultural policy to suppress rice production, a rather rare situation occurred in one prefecture in Japan that rice and winter wheat were grown in fields neighboring each other, rice being grown from May to October, and wheat from November to June of the next year. Grains of such rice and wheat were analyzed for cadmium (Cd) and lead (Pb) by atomic absorption spectrometry, and eight nutrient minerals by inductively coupled plasma emission spectrometry. Concentrations of nutrient minerals were higher in wheat grains than in unpolished rice grains (without husk), and similar trends were observed also for Cd and Pb. Flour obtained by milling of the wheat grains had significantly less Cd and nutrient minerals than the mother grains, and such reduction was also observed by treatment of unpolished rice to polished grain. Pb concentration was also reduced by the polishing of rice. Pb in wheat flour appeared to be higher than that in whole grain. Comparisons between the final edible forms of the two cereals showed that K and cu were higher in polished rice than in wheat flour and that such may also be the case for Cd, whereas the reverse was the case for Ca and Fe, and possibly for Pb.

Use of a food composition database to estimate daily dietary intake of nutrient or trace elements in Japan, with reference to its limitation

Daily dietary intake of 28 trace elements (Al, As, B, Ba, Be, Bi, Cd, Co, Cr, Cu, Ga, Ge, Li, Mg, Mn, Mo, Ni, Pb, Sb, Sc, Se, Si, Sn, Sr, Ti, Tl, V and Zn) were estimated from the food intake records (collected by the 24-h total food duplicate method), taking advantage of recently published trace element composition tables for foods in Japan. Because the number of food items listed in the tables was not sufficient, the calculation was made with not all foods recorded, and the results should be taken as semi-quantitative. The estimated intake was high (i.e. > 1 mg/day as a median) for Al, Cu, Mg, Mn, Si, Sr and Zn, medium (i.e. 2-985 micrograms/day) for As, B, Ba, Be, Cr, Ge, Mo, Ni, Sb, Sc, Se, Sn and Ti, and low (i.e. < 1 microgram/day) for Cd, Co, Li, Pb and V. Comparison of the present estimates with the reported values in the literature on 15 elements showed that close agreements were observed in the cases of 10 elements (i.e. Al, B, Cr, Cu, Mg, Mn, Mo, Ni, Se and Zn) for which the present estimates are above 1 microgram/day, whereas the discrepancies were significant for four elements (i.e. Cd, Co, Pb and V) with < 1 microgram/day intake. When the expected dietary uptake was compared with that by respiration in the cases of the 16 elements for which the atmospheric concentration data in Japan are available, the uptake was exclusively attributable to the dietary route for all 16 elements with the possible exception of vanadium.