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douard
Bastarache fills us in on the dangers of cadmium in the making
of ceramics. The toxicology of ceramic materials is often underestimated
and sometimes neglected in our ceramics institutions. Many thanks to Edouard
for this contribution to ceramic toxicolgy.
Compounds:
- cadmium oxide
- cadmium carbonate
- cadmium chloride
- cadmium sulfate
- cadmium sulfide
Uses:
The metal is used in electroplating, in solder for aluminium, as a constituent
of easily fusible alloys, as a deoxidizer in nickel plating, in process
engraving, in cadmium-nickel batteries, and in reactor control rods. Cadmium
compounds are employed as TV phosphors, as pigments in glazes and enamels,
in dyeing and printing, and in semi-conductors and rectifiers.
Exposure:
Inhalation
Toxicology:
- Cadmium oxide fume is a severe pulmonary irritant; cadmium dust is a less potent irritant than cadmium fume because it has a larger particle size. Chronic exposure is associated with nephrotoxicity. Several inorganic cadmium compounds cause malignant tumors in animals.
- Inhalation exposure to high levels of cadmium fumes or dust is intensely irritating to respiratory tissue. Particle size appears to be a more important determinant of toxicity than chemical form. However, most acute intoxications have been caused by inhalation of cadmium fume at concentrations that did not provide sufficient warning symtoms of irritation. Concentrations of fume responsible for fatalities have been 40 to 50 mg/m3 for 1 hour or 9 mg/m3 for 5 hours. There has been non-fatal cases at lower concentrations. Pulmonary symptoms and clinical signs reflect lesions ranging from nasopharyngeal and bronchial irritation to pulmonary edema with also possibly headache, chills, muscle aches, nausea, vomiting, and diarrhea. Among survivors, the subsequent course is unpredictable; most cases resolve slowly, but respiratory symptoms may linger for several weeks, and impairment of pulmonary function may persists for months.
- Long-term inhalation exposure at low levels leads to decreased lung function and emphysema.
- Chronic exposure to cadmium results in renal damage which may continue to progress even after exposure ceases.
- Other consequences of cadmium exposure are :
- anemia
- yellow discoloration of the teeth
- rhinitis
- occasional ulceration of the nasal septum
- damage to the olfactory nerve
- anosmia
- Chronic exposure to high levels of cadmium in food has caused bone disorders, including osteoporosis and osteamalacia. Long term ingestion, by a Japanese population, of water and food contaminated with cadmium, was associated with a crippling condition, "itai-itai" (ouch-ouch) disease. The affliction is characterized by pain in the back and joints, osteomalacia (adult rickets), bone fractures, and occasional renal failure, and most often affects women with multiple risk factors such as multiparity and poor nutrition.
- Occupational exposure to cadmium has been implicated in a significant increase of lung cancer. The IARC has determined that there is sufficient evidence in humans for the carcinogenicity of cadmium and cadmium compounds. It also appears that cadmium has the capability to alter genetic materials, particularly chromosomes.
- The 1995 ACGIH threshod limit value-time-weighted average (TLV-TWA) for elemental cadmium and compounds as Cd is 0.01 mg/m3 for total particulate dust (while it is 10mg/m3 for titanium dioxide in Quebec); or 0.002 mg/m3 for the respirable fraction of dust,there is an A 2 suspected human carcinogen designation for both forms.
- The urinary excretion of cadmium itself bears no known relationship to the severity or duration of exposure and is only the confirmation of absorption.Absorbed cadmium is retained in the body to a large extent, and excretion is very slow.
Reference :Chemical Hazards of the Workplace, Proctor & Hughes, 4th edition.
Edouard Bastarache M.D. (Occupational & Environmental Medicine)
edouardb@sorel-tracy.qc.ca
http://sorel-tracy.qc.ca/~edouardb/