Effect tests Normal  Mild exposure students  High exposure students Mean ± s(n) % Mean± s(n) p % Mean ± s(n) p % r Age 21.45 ± 1.68(35) 33.03 22.32 ± 1.36(25) 0.01* 34.7 21.17 ± 2.5(35) N.S 32.5   Time of exposure 14.2 min ± 1.22(35) 3.80 1.80 hr ± 0.4(25) -- 29.7 4.02hr ± 0.95(35) -- 66.4 0.46* AChE activity *10-15  Mol/min 4.23 ± 1.27(35)  29.7 4.89 ±1.04(25) 0.003** 34.3 5.11 ± 1.27(35) 0.0001*** 35.9   p*: significant, p** : very significant, p*** : highly significant, N.S: no significance

Table 2: Frequency of RBC-AChE activity in relation to a history of students’ duration exposure.