ABSTRACT
Hydrogen sulfide is a toxic gas about which much has been written. It constitutes one of the most serious chemical hazards to which sewage network workers are exposed to. The current work aimed at assessment of cognitive dysfunctions among workers of sewer networks and the relation of these changes, if any, to the level of exposure to the biomarker, urinary thiosulfate. A trial for setting a screening test for cognitive function change. The work was conducted among 34 male workers involved in the maintenance of the sewage network and a matched unexposed control group [n = 21]. The participants were subjected to clinical neurological examination, estimation of urinary thiosulfate as hydrogen sulfide exposure biomarker, and assessment of cognitive functions changes by using neurophysiological [simple reaction time, P300 test] and neuropsychological tests [Wechsler Memory Scale] and frontal executive functions. Clinical neurological history revealed significantly higher neurological symptoms [headache, memory defects, lack of concentration] among exposed workers compared to their controls [P < 0.05]. Marked elevation of urinary thiosulfate was observed among the exposed workers [P < 0.001] although this elevation was not correlated with the duration of exposure. Exposed workers showed poor performance of most of neuropsychological tests compared to control subjects. Significantly prolonged simple reaction time and delayed P300 latency were found among sewer network workers. Most of exposed workers had significantly lower Mini-Mental State Examination [MMSE] scoring than that of the controls [P < 0.001]. MMSE was significantly correlated with other neuropsychological tests. Exposure of sewer network workers is associated with significant cognitive dysfunction which can be screened by applying MMSE annually as a screening test of the exposed workers