Prpic-Majic, D., Bobic, J., Simic, D., House, D. E., Otto, D. A., Jurasovic, J., and Alica Pizent
A cross-sectional study was performed on 275 pupils (144 boys and 131 girls) from the third and fourth grade of three elementary schools in Zagreb, Croatia, in order to provide relevant data on the relationships between characteristic indicators of lead exposure / health effects including hematological condition and some psychological functions. According to school locations, traffic density was the lowest in the street near school 1 and highest in the vicinity of school 2, while traffic density near school 3 ranged in density between school 1 and school 2. Air lead concentration was measured continuously in the vicinity of school 2, where the average value never exceeded 1 micro g Pb/m^3. In each pupil the intensity of lead absorption was determined by analyses of blood lead (PbB), erythrocyte delta-aminolevulinic acid dehydratase (ALAD), and erythrocyte protoporphyrin (EP). Lead in erythrocytes (PbE) was calculated by the PbB and corresponding hematocrit (Hct) value. The hematological condition of pupils was tested by hemoglobin (Hb) and Hct determination. Psychological examination included assessment of general cognitive development, visual motor integration, attention and complex psychomotor reaction. General intellectual status was evaluated by Wechsler Intelligence Scale for Children - Revised. Verbal subtests were: Information, Comprehension, Arithmetic, Similarities and Digit span, which were used to estimate verbal intelligence quotient (VIQ). Nonverbal subtests were: Picture completion, Picture arrangement, Block design, Object assembly and Coding, which were used to estimate nonverbal intelligence quotient (NIQ). All ten subtests were used to estimate general intelligence quotient (IQ). Visual motor integration was estimated by Bender Gestalt Test (BG) with an objective Göttingen scoring system. The quality of performance was scored by the number of errors in nine drawings. Attention and complex psychomotor reactions were assessed using the Complex Reactionmeter Drenovac. The total time (in ms) was determined by measuring simple psychomotor reaction to sound stimulus (S) and to light stimulus (L), as well as complex reaction time (4A) by measuring different complex psychomotor reaction. In each test the number of errors (SE, LE, 4AE) was also determined. Both parent and teacher ratings of child behavior were assessed by means of an extensive questionnaire. The socio-economic background of the family was assessed through the parent's education status, i.e. exact length of education for each parent, that may act as proxy for parents' IQ. Means and their 95% confidence limits were compared among the schools. Multiple stepwise regression analysis was performed for each of the 20 measured dependent psychological variables, standardized for school and gender, with age and six indicators of lead absorption and hematological condition as independent variables. Criterion for entry was p school 3 >school 2) and partly in PbB and PbE value (school 1 < school 2). The values of hematological indicators (Mean and 95% CI - Hb: 136.7, 135.8 to 137.7 g/L ; Hct: 39.5, 39.3 to 39.7) were in the expected range for Croatian children. The summarized results (N=275) of psychological examinations (Mean and 95% CI - VIQ: 112.9, 111.6 to 114.3 ; NIQ: 111.9, 110.4 to 113.4 ; IQ: 113.7, 112.3 to 115.0 ; BG: 7.9, 7.5 to 8.4 ; S: 449.5, 441.5 to 457.5 ms ; L: 578.4, 568.3 to 588.5 ms ; 4A: 740.4, 704.9 to 776.0 ms ; SE: 1.36, 1.15 to 1.56 ; LE: 1.51, 1.30 to 1.73 ; 4AE: 13.67, 12.62 to 14.71) were also in the expected range. In relation to schools, there were no consistent differences in the scores for psychological performance, contrary to what was expected, having in mind the differences in lead absorption. The sequence of scores for VIQ, NIQ and IQ (school 1 < school 3 < school 2) and the sequence of scores for BG (school 1 > school 3 > school 2) were in the opposite direction then expected in relation to the respective lead absorption. These findings indicate that factors other than lead were responsible for differences in psychological performance. When parents' years of education were included with age, lead absorption indicators, and hematological indicators as independent variables in regression analysis with 20 dependent psychological variables, age and parents' education were the only independent variables significantly associated with psychological variables. One or both parents' years of education were significant (p