[Health effects on workers exposed to low concentration carbon monoxide at high altitude]

Workers exposed to carbon monoxide (CO) at a concentration of 26.8mg/m3 at an altitude of 2,300 metres above sea level were compared with a control group of local inhabitants. There were significant differences in symptoms of headache, vertige fatigue and weakness memory impairment, insomnia, palpitation and neurobehavioral functions. CO concentration in respiratory air and HbCO in blood was higher but partial pressure of oxygen (PO2) and saturation of oxygen (SaO2) in blood was lower in the exposed group than the control group. Self-comparison of CO in respiratory air and HbCO in blood was higher after work than before work. Neurasthenia rate was significantly higher but PO2 and SaO2 significantly lower at high altitude than in the plain. The results indicated that under same CO concentrations the hazards to workers at high altitude were greater than to those working in the plain. The author recommends that at high altitude the CO permissible level should be appropriately lowered.