Workers in industries manufacturing cadmium pigments or refining cadmium metal may be exposed to cadmium dust or fume. Cadmium has a very long half-life, accumulating in liver and kidney, and long-term exposure can cause renal tubular dysfunction, disturbed calcium metabolism resulting in osteomalacia and osteoporosis, and probably an increased risk of lung and prostate cancer. Improved working standards have decreased cadmium pollution both at work and in the environment and so serious local outbreaks of cadmium toxicity, such as occurred in Japan in the 1950s and ’60s, are now less likely.
The half-life of cadmium in blood is about 2.5 months and so its measurement in whole blood is a good indicator of recent cadmium exposure. Urinary cadmium, in contrast, does not relate to recent exposure but reflects body burden better. At age 50, it is present at levels of 15 to 50 mg/kg in kidney. If the level exceeds 200 mg/kg then risk of renal damage is high. Urine cadmium excretion is low until its concentration in the kidney reaches a critical concentration. Hence blood monitoring is a better indicator of recent exposure.
Tobacco is a significant source of cadmium. Cigarette smokers have raised blood and tissue cadmium concentrations and heavy smoking (2 packs per day) can result in a 20 year accumulation of 15mg/kg.
The detection of increased urinary excretion of low molecular mass protein is a recognised way of monitoring for cadmium toxicity and estimation of urinary excretion of alpha-1-macroglobulin or retinol binding protein may be useful in this respect.
Sample Requirements and Reference Ranges for Cadmium
|Sample Type||Whole blood, random urine|
|Container||EDTA, universal container|
|Precautions||Urine samples for occupational exposure should be taken as random samples at the end of a working shift.|
|Minimum volume*||Whole blood: 250 µL
Urine: 1 mL
|- whole blood||< 50 nmol/L
MHRA action limit: 120nmol/L (7 µg/L)
|- urine||< 1.6 nmol/mmol creatinine|
|Turnaround time||2 weeks|
|Method||Urine: Graphite furnace/atomic absorption spectrometry
Blood: Inductively coupled plasma mass spectrometry