Blood cadmium levels in the populations of Masan, Korea, and Miyagi, Japan: an inter-regional comparison

Time trend of cadmium intake in Korea

OBJECTIVES

The aim of this study was to elucidate past and current levels of cadmium (Cd) intake among the general populations in Korea.

METHODS

For this purpose, publications reporting dietary intake of cadmium (Cd-D), cadmium concentration in blood (Cd-B) and that in urine (Cd-U) in Korea were retrieved through literature survey for a period from 1975 to 2015.

RESULTS

In practice, 9, 21 and 14 articles were available on Cd-D, Cd-B and Cd-Ucr (Cd-U as corrected for creatinine concentration), respectively. Linear regression analyses of the reported values as a function of years (i.e., the year when each survey was conducted) showed steady decreases in all of the three exposure markers of Cd-D, Cd-B and Cd-U(cr). Factors possibly contributing for the reduction were discussed including the government-set guideline of 0.2 mg/kg for rice and changes in food habits among general populations.

CONCLUSIONS

There have been steady decreases in Cd-D, Cd-B and Cd-U(cr). The current estimates for Cd-D, Cd-B and Cd-Ucr were 6.0-7.4 μg/day, 0.73-0.83 μg/L and 0.60-0.95 μg/g cr, respectively.

Safe levels of cadmium intake to prevent renal toxicity in human subjects

The present review attempts to provide an update of the scientific knowledge on the renal toxicity which occurs in human subjects as a result of chronic ingestion of low-level dietary Cd. It highlights important features of Cd toxicology and sources of uncertainty in the assessment of health risk due to dietary Cd. It also discusses potential mechanisms for increased susceptibility to Cd toxicity in individuals with diabetes. Exposure assessment on the basis of Cd levels in foodstuffs reveals that vegetables and cereals are the main sources of dietary Cd, although Cd is also found in meat, albeit to a lesser extent. Cd accumulates particularly in the kidney and liver, and hence offal contains relatively high amounts. Fish contains only small quantities of Cd, while crustaceans and molluscs may accumulate larger amounts from the aquatic environment. Data on Cd accumulation in human kidney and liver obtained from autopsy studies are presented, along with results of epidemiological studies showing the relationship between renal tubular dysfunction and kidney Cd burden. These findings suggest that a kidney Cd level of 50 μg/g wet weight is a maximum tolerable level in order to avoid abnormal kidney function. This renal Cd burden corresponds to a urinary Cd excretion of 2 μg/d. Accordingly, safe daily levels of Cd intake should be kept below 30 μg per person. Individual variations in Cd absorption and sensitivity to toxicity predicts that a dietary Cd intake of 30 μg/d may result in a slight renal dysfunction in about 1 % of the adult population. The previous guideline for a maximum recommended Cd intake of 1 μg/kg body weight per d is thus shown to be too high to ensure that renal dysfunction does not occur as a result of dietary Cd intake.

A global perspective on cadmium pollution and toxicity in non-occupationally exposed population

Cadmium is a non-essential element that has high rates of soil to plant transference compared with other non-essential elements, and certain plant species accumulate large amounts of cadmium from low cadmium content soils. In this paper, levels of cadmium found in major food groups are highlighted together with cadmium levels found in liver and kidney samples from non-occupationally exposed populations. Data on human kidney cadmium levels identified recently, including the study in our own laboratory, are compared with older studies. Human-tissue cadmium contents showed large variations among individuals, but sources of the variation remain unknown. Exposure levels of 30-50 microg per day have been estimated for adults and these levels have been linked to increased risk of bone fracture, cancer, kidney dysfunction and hypertension. Increased mortality was found among individuals showing signs of cadmium renal toxicity compared with those without such signs, suggesting that renal toxicity may be an early warning of complications, sub-clinical or clinical morbidity.

Cadmium levels in the lung, liver, kidney cortex, and urine samples from Australians without occupational exposure to metals

The authors undertook this study to assess levels of cadmium exposure in the general population. Samples of lung, liver, and kidney were obtained from 61 cadavers (43 males, 18 females; 2-89 yr of age, mean age = 38.5 yr) who died from accidental causes and who were subject to postmortem examinations at the John Tonge Centre for Forensic Sciences, Queensland Health Scientific Services, Brisbane, Australia, in 1997 and 1998. Samples of bladder urine were also obtained from 22 cadavers. Tissue and urine samples were analyzed for cadmium, zinc, and copper with inductively coupled plasm (ICP) mass spectrometry. The overall mean values for cadmium in the lung, liver, and kidney cortex samples were 0.13, 0.95, and 15.45 microg/gm wet tissue weight. The average renal cadmium level in subjects with high lung-cadmium levels (n = 13) was 6 microg/gm wet tissue weight higher than that of similarly aged subjects who had medium lung-cadmium levels (n = 30). In females, the average level of cadmium in the liver was 74% greater than in males, and the average liver cadmium in females with high lung-cadmium levels was 100% higher than in males in the same age range who had the same high lung-cadmium levels. Renal cadmium accumulation tended to be greater in females than in males who were in the same age range and who had similar lung-cadmium levels, a result that suggested that there was a higher absorption rate of cadmium in females. The mean value for a urinary cadmium excretion of 2.30 microg/gm creatinine was found in a subset of samples that had a mean age of 39 yr and a renal cortex cadmium concentration of 18.6 microg/gm wet tissue weight. Urinary cadmium excretion rates were correlated more strongly with lung and kidney cadmium content than with age or liver cadmium levels. The results suggest that urinary cadmium excretion may be increased in smokers and could provide some estimate of body cadmium burdens in future Australian epidemiological studies.

Reduction in cadmium in blood and dietary intake among general populations in Japan

Blood samples and 24-h duplicates of food were collected in the years around 1980 and then in 1990's from inhabitants of nonpolluted regions in Japan. The 1990 study is still in progress with 286 blood samples and 125 food duplicates already collected from 7 regions. A preliminary analysis is made in the present study with the data obtained from the 7 study regions where the survey was conducted in 1980 and then in 1990, to examine possible changes in dietary cadmium intake (Cd-D) and consequently cadmium levels in blood (Cd-B) during this 10 year period. The food duplicate analysis showed that Cd-D in 1980 was 47.1 micrograms/day (1.74):65 [GM (GSD):N] for men and 27.7 micrograms/day (1.75):65 for women. The counterpart values in 1990 were 29.5 micrograms/day (1.66):40 for men and 23.8 micrograms/day (1.73):85 for women; the difference between the two values for the same sex is significant (P < 0.05) both in men and in women, suggesting that there occurred about 37% and 14% reduction in dietary cadmium intake during this 10 year period in men and in women, respectively. Comparison in Cd-B showed that Cd-B for men and women in 1990 were 1.79 micrograms/l (2.01):121 and 1.84 micrograms/l (1.67):165, respectively, whereas the counterpart values in 1980 were 3.84 micrograms/l (1.64):123 and 3.57 micrograms/l (1.42):141, respectively, indicating significant (P < 0.01) reduction in Cd-B in both sexes in parallel to the reduction in Cd-D.(ABSTRACT TRUNCATED AT 250 WORDS)