Soichiro Iwao

Increased urinary beta 2-microglobulin in cadmium exposure: dose-effect relationship and biological significance of beta 2-microglobulin.

A study on the general population from both cadmium-polluted and control areas and on cadmium alloy workers indicates that beta 2-MG in urine is very closely correlated with aging, but it indicates an association with cadmium exposure. However, the age factor is stronger than cadmium exposre in both polluted and control areas among persons without clinical proteinuria. On the other hand, cadmium exposure is most likely correlated with beta 2-MG even in nonpolluted areas. Thus it seems that there is no noneffect level of cadmium dose in affecting the elevation of beta 2-MG in urine. beta 2-MG in serum indicated a very close correlation with cadmium in blood among cadmium alloy workers. This may suggest that an increase of beta 2-MG in both blood and urine in an early stage of cadmium exposure is caused by the increased level of beta 2-MG in blood, which may be a result of stimulation due to cadmium, but not necessarily by the clinical dysfunction of reabsorption of beta 2-MG in the renal.

Variation of Cadmium Accumulation among Japanese

Human liver, renal cortex, and heart muscle from 394 autopsied Japanese who had lived in eight districts of Japan were sampled. Subjects included 200 males between 0 to 89 yr of age and 194 females between 0 to 94 yr of age. Cadmium, copper, and zinc in both liver and renal cortex, as well as cadmium in heart muscle were compared by district, sex, age, and smoking habits. Statistical results revealed that the difference of each heavy metal distribution by eight districts is significant and that cadmium and zinc levels in liver and renal cortex sampled from north-central Japan were the highest. This probably results from the larger intake of dietary cadmium and zinc via rice since this area is known as one of the better rice growing regions in Japan. Although there is a lack of precise information on smoking habit, cadmium in liver and zinc in liver and renal cortex of males smoking eight or more cigarettes per day were statistically higher than that of nonsmokers and those who smoked less than seven cigarettes per day. However, cadmium in renal cortex was not significant between the two smoking groups. Further studies should be performed to determine the health significance of an increased intake of cadmium by populations from the viewpoint of global biogeochemistry.

Effects of Airborne Fluorides on Workers at a Cryolite Production Plant

Workers in a cryolite-producing plant were the subjects of this study to identify the relationship between environmental exposure to fluoride compounds and urinary fluorine excretion. Workers were divided into three groups according to the process of cryolite production (a calcination unit and two units producing cryolite by different methods). Both the airborne fluoride concentration and the urinary fluorine concentration of workers were monitored twice a year from 1977 to 1982. Urinary fluoride levels before and after work were obtained to minimize the influence of factors other than occupational exposure which affect the body burden of fluorides. Due to improvements in the work process during the observed period, by 1982 the dust exposure level in the calcining process had been reduced to one-tenth the level in 1977. In the precalcining process, environmental hydrogen fluoride levels were closely correlated to the urinary fluoride levels of workers. Significant correlations to the urinary fluorine levels of workers in cryolite production and the recovery of fluorides were also found. As a result, urinary fluoride concentration is considered to be a good indicator for monitoring the effects of fluoride compounds on workers’ health.

Associations of cadmium with zinc and copper in cancer cases and controls

This study was performed in order to search for possible associations between cadmium (Cd) and other metals~ Cd, zinc (Zn), and copper (Cu) levels of renal cortex and liver samples obtained from 196 cancer cases and 198 noncancer controls were analyzed in eight regional institutes in Japan. Cd, Zn, and Cu concentrations in liver and renal cortex of the selected cancer cases were compared to the controls whose localities, age, and sex were matched with the cancer cases. The cancer cases clearly showed higher accumulations of Zn in liver and renal cortex than the noncancer group. Cd showed a similar tendency, but there was no statistical significance between case and control subjects. There was no marked difference in Cu accumulation between the pairs.The best fit regression curve of Zn to Cd on a molar basis in renal cortex was obtained. Curvilinear regression equations of Zn to Cd for both cancer and noncancer groups were drawn. From these two equations, the Zn level of the cancer cases was found to reach a maximum when the Cd level showed 1.4 mmol/kg (157 pxg/g), whereas Zn in the noncancer group peaked at 1.6 mmol/kg (180 Ixg/g) of Cd in renal cortex. This may suggest that excessive Cd accumulation deprives binding sites of Zn in renal cortex when both metals are saturated.