Hydrogen sulfide exposure without loss of consciousness: chronic effects in four cases.

Adverse effects of acute exposure to hydrogen sulfide (H2S) are well documented, but long-term effects of occupational exposure to low levels of the gas are not. To evaluate effects of such exposure we performed physical, neurologic, psychiatric, and chemosensory (smell and taste) examinations of four workers who were present but did not lose consciousness when the gas was accidentally released at a construction site. None of the four workers tested positive for functional problems, but all met diagnostic criteria for at least three, and up to eight, H2S-induced neuropsychiatric clinical disorders and from zero to two subclinical disorders. All four had abnormal P300 evoked responses (electrical neurophysiologic tests of brain waves). Our data indicate that exposures to even relatively low concentrations of H2S are hazardous. A rigorous epidemiologic investigation of persons who work with H2S is warranted.