NEURODEVELOPMENTAL ASSESSMENT OF CHILDREN EXPOSED TO MERCURY IN PALAWAN . Nelia P.C. Maramba 1, Jose Paciano Reyes 1, Carissa Paz Dioquino 1, Nerissa M. Dando 1*, Lynn Crisanta R. Panganiban, 1 Ana T.F. Rivera 2, Ma. Teresa Castillo 2, Rhodora Reyes 2, Carmela Quitoriano 2, Meredith Afuang 2, Rene Timbang 2

1 National Poison Management and Control Center , Philippine General Hospital – College of Medicine , University of the Philippines , Manila
2 Department of Health, Republic of the Philippines

 Clinically evident neurological damage such as severe cerebral palsy from methylmercury exposure was described following poisoning episodes in Japan and in Iraq in the early 1970’s. The developing nervous system is especially vulnerable to effects of methylmercury exposure with fetuses and neonates as the most sensitive subpopulation. In the United States , the National Research Council and the Environmental Protection Agency recommended a reference dose (RfD) of 0.1 ug/kg bw/day level of methylmercury exposure for maternal-fetal pairs. Thus RfD is aimed at protecting children from delays and deficits in neurological development secondary to exposure to methylmercury in utero. These deficits result in an increased prevalence of scores on tests of learning that are in the lowest 5% of the distribution.

Fetal type methylmercury poisoning also occurred in Iraq and the growth and development of children were investigated which showed that a 5% of risk of delayed walking of abnormal central nervous system function was implied when the peak concentration in the hair of the mother during pregnancy was within the range of 10~20 ug/g. Data from the Iraqi episode in the 1970’s was used by the regulatory agencies to establish NOAELs (no Observed Adverse Effect Levels) as well as reference doses. However, in recent years it became increasingly evident that these data may not be appropriate for risk assessment.

Objective: To evaluate the neurodevelopmental effects of mercury among children and to correlate levels of various mercury compounds with its effects.

Methodology: Twenty-five (25) pregnant women and infant pairs with the same proportion of mother and child from the study site and 10 pairs from the same sub-groups in the control were included in this study based on the inclusion and exclusion criteria. Social preparation and informed consents were obtained. A validated interview tool prepared in the local dialect was used to document demographic data, health practices and medical histories. Complete physical, mental status, neurological examination including Screening Behavioral Inventory (SBI) and Denver Developmental Screening Test (DDST II) among mothers, infants and children, whichever is applicable at the time of examination were conducted. Blood, hair and urine specimen were obtained for each subject. The following tests were done for blood samples: total mercury and methylmercury levels, blood urea nitrogen, creatinine, alanine aminotransferase, aspartate aminotransferase Hair total mercury and methylmercury levels were determined.

Results: A total of 66 children, 43 exposed and 23 control, were initially seen aged 0 – 3 years old. Of the 43 exposed children, 31 (72.1%) achieved normal scores for age in their developmental tasks, 10 (23.3%) were considered “Suspects” and 2 (4.6%) were “Untestable”. While for the 23 controls, 17 (73.9%) are “ Normal ”, 6 (21.7%) “Suspect” and 1 (4.3%) “Untestable”. Most children failed in areas of Language (21% in exposed, 26% in control). Exposed children (19%^) achieved low scores in Gross Motor Skills than controls (13%) while they scored higher in Fine Motor Adaptive Skills (7% for exposed, 17% for controls) and Personal Social Skills (5% for exposed, 9% for controls).

Name: DR. NERISSA M. DANDOPosition Title: Clinical Toxicology Consultant
Organization: National Poison Management And Control Center
Philippine General Hospital - College of Medicine
University of the Philippines Manila
Address: Room 100, Ward 14 – A, Philippine General Hospital
Taft Avenue , Ermita, Manila Philippines
Country: Philippines Postal/Zip Code: 1000
Phone (work): (632) 4040257 Fax: (632) 5260062)
(632) 5241078
(632) 5218450 local 2311
E-mail: docirisd@yahoo.com

Keywords: neurodevelopment, methylmercury, total mercury, palawan