Cadmium and its inorganic compounds - expressed as Cd - inhalable fraction. Documentation of proposed values of occupational exposure limits (OELs)
Authors: Daragó Adam , Sapota Andrzej , Jakubowski Marek 
Published: December 2019

Cadmium (Cd) is a white metal with a bluish tint. It forms a number of compounds occurring in them on the degree of oxidation 2+. Cadmium compounds are water-soluble to varying degrees.
The highest risk groups include employees involved in the production of nickel-cadmium batteries, alloys, cadmium pigments as well as employees of non-ferrous metal smelters and cutting welders of metals covered with a cadmium anti-corrosion layer. According to the Central Register of Data on Exposure to Substances , Preparations, Factors or Technological Processes on Carcinogenic or Mutagenic Action, 4276 workers in Poland were exposed to cadmium and its compounds.
Cadmium is absorbed into the body through inhalation and digestive systems. In humans, the absorption is 2–50% and 4–6%, respectively. Elimination of cadmium from the body is a slow process. The estimated half-life of cadmium is from 5 to 30 years.
Results of studies conducted in subjects exposed to cadmium in the work environment showed that the threshold concentration of cadmium in urine, at which increased excretion of low molecular weight proteins in urine was found, is 5–10 µg/g creatinine.
In 1993, IARC identified cadmium and its compounds as a human carcinogen (group 1). The results of experimental studies in rats provided evidence of cadmium carcinogenicity as a result of inhalation exposure.
Cadmium is recognized by SCOEL as a category C carcinogen, i.e. as a genotoxic carcinogen for which a threshold of action (concentration) can be determined, also called a practical threshold.
The critical organs for the toxic effects of cadmium and its inorganic compounds in humans, depending on the route of exposure, are kidneys, lungs and possibly bones. The critical effect of cadmium on kidneys is increased excretion of low molecular weight proteins in urine, while the critical effect on lungs is the carcinogenic effect.
Inhalation studies in rats exposed to cadmium at concentrations of 30 µgCd/m3, 13.4 µgCd/m3 and 10 µgCd/m3 for 18 months were used as the basis to propose TLV-TWA. The concentration of 10 µg Cd/m3 was taken as the NOAEL value. After applying the formula and taking into account the uncertainty factors with a total value of 10, the concentration of 0.001 mg/m3 (1 µgCd/m3) was determined as the TLV-TWA value for the inhaled fraction. Biological monitoring is the best indicator of cadmium exposure. The excretion of cadmium in urine enables the assessment of cumulative cadmium in the body and takes into account all sources of cadmium exposure, including contaminated food and smoking, while the blood cadmium concentration is a measure of current exposure.
Previous BEI values in blood and urine were 5 μgCd/l and 5 μgCd/g creatinine, respectively. After discussion at the 91st meeting of the Interministerial Committee for TLVs and PELs, these values were maintained as mandatory.
This article discusses the problems of occupational safety and health, which are covered by health sciences and environmental engineering.