Environmental Medicine Integrating a Missing Element into Medical Education (1995) / Chapter Skim
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Case Study 6: Cadmium Toxicity
Case Study 6: Cadmium Toxicity
Pages 224-243
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From page 224... ...
ED Cadmium affects primarily the renal and skeletal systems. This monograph is one in a series of self-instructional publications designed to increase the primary care providers knowledge of hazardous substances in the environment and to aid in the evaluation of potentially exposed patients.
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On examination you find a thin female with a slightly stooped posture and a waddling gait. Blood pressure is 120170.
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Like most plants, tobacco contains cadmium, which is inhaled in cigarette smoke. Cadmium concentrations in drinking water supplies are typically less than 1 microgram per liter (lig/L)
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, a rate roughly ten times lower than that required to cause critical renal effects. Acute cadmium toxicity is rare because very high levels are seldom encountered in the workplace today, and low doses are not acutely toxic.
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For example, the permissible exposure limit (PEL) of cadmium fume or cadmium oxide in the workplace is 100 micrograms per cubic meter of air (100 ~g/m3)
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(2J Why is the patient described in the case study at increased risk of cadmium toxicity?
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However, when renal damage from cadmium exposure occurs, the excretion rate increases sharply, and urinary cadmium levels no longer reflect body burden. The total cadmium body burden at birth is less than 1 pal, which gradually increases with age to about 30 milligrams (mg)
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From page 231... ...
Proteinuria appears to be irreversible, and continued exposure can lead to progressive renal dysfunction. Typically the proximal renal tubules are affected, resulting in a Fanconi-like syndrome with urinary excretion of low molecular weight proteins such as 82-microglobulin, Iysozyme, and retinolbinding protein.
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From page 232... ...
. Studies have associated chronic cadmium inhalation with pulmonary function impairment, notably mild emphysema and pulmonary fibrosis with reduced ventilatory capacity.
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In a Swedish epidemiologic study of pregnant women exposed to high cadmium concentrations in the workplace, an increased incidence of infants with low birth weight was reported. Other Effects Chronic cadmium exposure has been reported to cause mild anemia, anosmia, yellowing of teeth, and, occasionally, liver damage.
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From page 234... ...
Inhalation exposure most often occurs among workers and hobbyists when cadmium fumes are produced by hightemperature processes such as welding, smelting, and soldering, and where cadmium dust results from grinding. In the general population, ingestion of cadmium-contaminated food is more likely to occur than inhalation of cadmium particles.
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Chronic cadmium intoxication may also play a role in the development of hypertension, although the association is weak. Anosmia and yellow discoloration of teeth near the gum line may be noted.
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From page 236... ...
The amount of cadmium excreted then increases dramatically, reflecting recent exposure rather than total body burden. When urinary cadmium levels are less than 10 p9/9 creatinine, renal dysfunction is considered unlikely.
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From page 237... ...
Once metallothionein binds to cadmium, the complex preferentially accumulates in the kidney. Urinary levels of metallothionein correlate well with urinary cadmium levels and can reflect total cadmium body burden; however, urinary concentration of the cadmium-metallothionein complex increases significantly once renal dysfunction has developed.
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From page 238... ...
Public health authorities should be notified whenever cadmium toxicity is suspected in a patient so that case-finding may be initiated and preventive measures taken. Acute Exposure O There 1e no specific antidote for cadmium poisoning.
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From page 239... ...
Standards and regulations for cadmium Agency Focus Lev l Comments ACGIH Air-Workplace cadmium dust 0.05 mg/m3 Advisory; TWA cadmium fume 0.05 Tend 1 5-minute ceiling limit NIOSH Air -Workplace N/A Advisory; lowest possible limit based on cardnogenTc risk OSHA Air-Workplace cadmium dust 0.2 mg/m3 Regulation; PELF cadmium fume 0.1 mg/m3 EPA A N/A Under review Water 0.01 ppm Regulation; maximum contaminant level in drinking water; suggested revision to 0.005 ppm WHO Food 0.4-0.5 me Advisory; provisionaltolerable weekly. intake for adults · ACGIH .
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EPA is seeking classification of cadmium as a hazardous air pollutant; however, no ambient air standard for cadmium currently exists. Water EPA has established a maximum contaminant level (MCL)
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Honda 8, Tsuritani I, et al. Progress of renal dysfunction in inhabitants environmentally exposed to cadmium.
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(3) Yes, the patient's husband also may be at increased risk of cadmium toxicity because of increased opportunity for exposure, although his risk is probably less than his wife 's.
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From page 243... ...
When proximal tubular damage occurs, cadmium excretion can result from two sources; breakdown of the tubular epithelium and decreased reabsorption. Under these conditions, urinary cadmium levels are likely to be markedly increased and no longer reflect body burden.
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