Date of Award

2009

Document Type

Thesis

Degree Name

Master of Science (MS)

Department

Environmental Science

First Advisor

D.'. Abdu Adem

Second Advisor

Dr. Hussain Attia

Third Advisor

Dr. Abdul-Kader Souid

Abstract

BACKGROUND: Environmental toxic metal exposure is well known to adversely affect children's development and behavior. To our knowledge, there are no studies that carefully examined this potential hazard in UAE and Gulf countries.

OBJECTIVES: The aim of this case-control study was to determine blood concentrations of 12 heavy metals in school-age children in Al Ain City. The other aim was to correlate the blood levels with developmental (e.g., learning disability) and behavioral (e.g., Attention Deficit/Hyperactivity Disorder) problems in children.

METHODS: One hundred and forty seven subjects (73 with developmental and/or behavioral disorders and 74 controls) participated in the study. The median age was 8 years (range, 5 -15). Raven's Colored Progressive Matrices Scale was used to assess the IQ. Whole blood samples were drawn in trace element-free vacuum tubes. ICPMS instrument was used to determine the metal concentration. Data analysis was performed using the SPSS-PC software package, version 15.0. Logistic regression and independent samples {-test were used. All statistical tests were performed at the 5% significance level.

RESULTS: The blood level (mean±SD, n=146) of lead was 25.86±13.06 ppb, cadmium 0.31±0.25 ppb, arsenic 10.74±4.71 ppb, mercury 1.39±1.16 ppb, manganese 1.85±1.09 ppb, nickel 9.18±8.23 ppb, zinc 3731±1752 ppb, chromium 2.1 0±1.53 ppb, cobalt 0.65±0.40 ppb, copper 1064±403 ppb, molybdenum 1.59±1.25 ppb, and antinomy 0.60±0.63 ppb. Higher levels of blood concentrations of lead, cadmium, arsenic, manganese, nickel, zinc, copper and molybdenum were significantly associated with a higher risk of developmental/behavioral disorders (p-value < 0.01); best predictors were manganese and molybdenum. Higher blood concentrations of lead, cadmium, arsenic, manganese, nickel, copper and molybdenum were significantly associated with a higher risk of learning disability (p- value ≤ 0.02); best predictor was molybdenum. An increase in blood concentrations of lead, manganese, zinc and copper was significantly associated with a higher risk of Attention Deficit/Hyperactivity Disorder (p-value < 0.02); best predictors were manganese and zinc. Increases in blood concentrations of cadmium, arsenic, manganese, nickel, copper and molybdenum were significantly associated with a below average IQ (≤ 25th percentile) (p- value < 0.05).

Associations (p-value < 0.05) between increments in blood levels of certain heavy metals and Child Behavior Check List syndromes (anxiety, depression, withdrawn, somatization, social problems, thought problems, attention deficit, delinquency, aggression, internalization and externalization) were noted. For example, nickel (best predictor), copper and molybdenum were significantly higher in the children with aggression.

CONCLUSIONS: The results show significant associations between heavy metal exposure and learning, developmental and behavioral problems in children. Even low levels of lead and other heavy metals can serve as potential risk factors for developmental and behavioral disorders. Surveillance linked to appropriate public health interventions is strongly recommended for UAE.

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