intelligence quotient level of the children living in high lead areas in zanjan province

background and objectives : considering the effect of heavy metals (particularly lead) on intelligent quotient level , it was measured in children living in high lead areas in angouran district of zanjan province . material and methods : in this historical cohort study all( n=64 ) grade – one students living in angouran village were selected as case group. 62 other students living in low lead areas , but with similar socio – economic , cultural and racial conditions were selected as the control group. in a double blind study using the wechler’s intelligence scale for children – revised ( wisc-r) the iq level of both groups were  calculated . this test is regarded as the most accurate test with 80-90% reliability . the iq of 90 or more is considered normal and less than this is low. by using chi-square the iq of the two groups living in high and low – lead areas were compared . the t-test and p- value with 95% reliability and the relative risk of decrease of iq due to living in high – lead areas were calculated . results :the average iq level in 64 children living in high lead area was 86.64+/-9.68 with 40 ( 62.5% ) having less than normal level. in comparison in the other group the average iq level was 91.98+/-10.26 with 24 of the children (38.7%)having less than normal level . the iq level in children living in high-lead area was significantly lower than children living in low- lead area( p<0.0031 ). discussion: although the serum level of lead was not determined but the results of this study are strongly in favor of the relationship between living in high-lead areas and low iq levels. preventive and therapeutic precautions are necessary in theses areas.