Neuropsychological tests were administered to 45 students exposed for 2 hours to carbon monoxide in low concentrations (mean, 61 ppm) from residential kerosene stoves and results compared to 47 nonexposed control students at the Hebrew, Haddasah, and Ben-Gurion Universities, Jerusalem, Israel. Venous blood carboxyhemoglobin levels ranged from 0.01 to 0.11. CO exposed students scored significantly lower on tests of memory, new learning ability, attention and concentration, tracking skills, visuomotor skills, abstract thinking, and visuospatial planning and processing. 
COMMENT. Low-level carbon monoxide exposure results in impairments of higher cognitive function similar to those previously reported in patients with moderate CO poisoning. Early symptoms of CO poisoning consist of headache and fatigue, followed by dizziness and syncope. Subtle signs of CO exposure may require psychological tests for their detection.