Cadmium, environmental exposure, and health outcomes

1. Cadmium, environmental exposure, and health outcomes Ben Guo

2. Background • Source: diet (high rate of soil-to-plant transfer) • Increased cancer incidence: accumulating of cadmium • Kidney is a specific target for cadmium accumulation.

3. Safe intake limit: 7ug cadmium/week/kg body weight (set based on the critical renal cadmium concentration between 100-200 ug/g wet weight which corresponds to a urinary threshold limit of 5-10 ug/g creatinine)

4. 1.FAO/WHO guidelines for safe intake • PTWI: provisional tolerable weekly intake • PTWI(WHO 1989): 400-500 ug/person/week • PTWI(WHO 1989): 7 ug/kg body weight/week • Renal cortical cadmium 50ug/g wet weight corresponds to urinary cadmium 2ug/g creatinine

5. However, kidney effects can be observed at urinary cadmium levels < 0.5 ug/g creatinine • Satarug and his colleagues’ studies suggested that the estimated intake of 25-30 ug/day may produce adverse kidney effects in about 1%of the adult population.

6. 2.Threshold-based models for safe intake • Bench-mark dose (BMD): the exposure level that produces a change in a response. • Japanese subjects: BMDL10 of urinary cadmium is 0.6-1.2 ug/g creatinine in men and 1.2-3.6 ug/g creatinine in women. • Swedish women: BMD of urinary cadmium is 0.6-1.1 ug/g creatinine.

7. In a word, the tolerable weekly intake for cadmium is 2.5 ug/kg body weight, which corresponds to 25 ug/day for a person who weighs 70kg. (European Food Safety Authority 2009)

8. 3.Cadmium sources and bioavailability • a. Mollusks and crustaceans Cadmium in oysters and shellfish is bioavailable and that long-term oyster consumption does result in a higher body burden of cadmium.

9. b. Oilseeds Cadmium in sunflower kernels possess a high nephrotoxic potential, they may indicate increased sensitivity to cadmium renal toxicity in the high sunflower-kernel consumers.

10. c. Offal In one study, Haswell-Elkins et al. found high cadmium body burden associated with higher consumption of turtle liver and kidney. Cadmium levels are higher in liver and kidney than in muscle and older animals.

11. 4.Cadmium exposure and effects observed • a. Kidney and bone 1.chronic high- dose effects: mainly affects women and is characterized by severely impaired tubular and glomerular function and generalized osteomalacia and osteoporosis that result in multiple bone fractures

12. 2.chronic low-dose effects: has been linked to tubular impairment with a loss of reabsorptive capacity for nutrients, vitamins, and minerals.

13. 3.current exposure levels compelling evidence has linked tubular impairment with urinary calcium loss, rapid bone demineralization and osteoporosis. environmental exposure to cadmium may constitute the risk factors for chronic kidney diseases.

14. b. Diabetes • c. Diabetic nephropathy • d. Hypertension • e. Lung disease • f. Periodontal tissues disease • g. Ocular tissues disease • h. Cancer: cadmium is classified as a cancer-causing agent.

15. 5.Cadmium body burden • a. Sex and tissue differential cadmium accumulation Younger individuals have high rates of renal cadmium accumulation. There is a trend for higher cadmium content in the kidneys of the female.

16. b. Intestinal absorption of metals, body burden variability, and metal transporters The possible intestinal absorption rate for cadmium is 3-7%. The people who had low iron stores usually had higher cadmium body burden.

17. 6.Conclusions • In the past, the wide variation in cadmium body burden among people has been attributed to cigarette smoking and the high pulmonary absorption rates of cadmium in cigarette smoke. • This review concerns about safe intake level that uses the kidney as the sole target in assessing the health risk from ingested cadmium

18. The persistence of cadmium in the environment requires a long-term approach to minimize human exposure through environmental management and maintenance of lower cadmium levels wherever possible.