Cadmium, environmental exposure, and health outcomes

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Cadmium, environmental exposure, and health
outcomes

• Ben Guo

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Background

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

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• 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)

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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

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• However, kidney effects can be observed at
  urinary cadmium levels lt 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 1of the
  adult population.

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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.

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• 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)

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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.

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• 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.

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• 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.

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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

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

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• 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.

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• 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.

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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.

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• 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.

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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

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• 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.