Prevalence of lead toxicity among secondary school students in Sohag city and its impact on cognitive functions

Lead is an extremely toxic metal. Lead intoxication in children has been associated with cognitive impairments. This study was designed to determine the prevalence rate of lead toxicity among secondary school children in Sohag City [Upper Egypt], sources of lead toxicity and the impact of lead toxicity on cognitive function of studied student. The studied students [600] were recruited from three schools, 200 students from Elaskaria school [main stream school] and 400 students from two technical schools [200 from industry and 200 from Elzekhrofia]. A control group was selected from the same sample of studied school, who proved to have normal urinary lead level [<50 micro g/L]. All studied students were subjected to body measurements, clinical evaluation, soft neurological signs, social level, psychometric tests [WAIS, CASI and WMS]. Urine sample were collected for assessment of lead level. The study revealed that the prevalence rate of lead toxicity was 50.5% and the highest rate among studied schools was reported in Elzekhrofia school [62%]. Sources of lead toxicity in this community were old houses [77.9%], presence of repair shops [60.8%], and garbage combustion 60.3%, and smoking [62.1%]. Soft neurological signs were significant abnormal among student with toxic urinary lead level [> 80 micro g/L] in comparison to student with normal lead level [<50 micro g/L] except in one test [standing on one foot]. Student with toxic urinary lead level [> 80 micro g/L] had inverse proportion with social level. There were statistically significant lower scores among students with pre clinical toxicity [>50-80 micro g/L] and toxic level than students with normal urinary lead [<50 micro g/L] in total, verbal and performance Wechsler adult intelligence scale [WAIS], in all Wechsler memory scale [WMS] subitems and in all cognitive abilities screening instrument [CASI] subitems