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PEDIATRICS Vol. 111 No. 3 March 2003, pp. e289-e295

ELECTRONIC ARTICLE

Tagum Study II: Follow-up Study at Two Years of Age After Prenatal Exposure to Mercury

Gloria B. Ramirez, MD, MHA*, Olive Pagulayan, MS.STAT, Hirokatsu Akagi, PhD, Pharm#, Ana Francisco Rivera, Chem Eng**, Lillian V. Lee, MD, MHA||, Anna Berroya, MD{ddagger}, Ma. Cristina Vince Cruz, MD, MHA§ and Dainah Casintahan, MD{ddagger}{ddagger}

* Research Development Office
{ddagger} Divisions of Neuroscience
§ Neonatology
|| Philippine Children’s Medical Center, Quezon City, Philippines
School of Statistics, University of the Philippines, Philippines
# Department of International Affairs & Environmental Sciences, National Institute for Minamata Disease, Philippines
** Department of Health, San Lazaro Compound, Tayuman, Sta Cruz, Manila, Philippines
{ddagger}{ddagger} Department of Pediatrics, Davao Regional Hospital, Tagum Davao City, Philippines

--> Objectives. To correlate the presence and levels of total mercury (THg) in cord blood and meconium indicating prenatal exposure with developmental milestones at 2 years and to compare these subjects with controls of comparable age using cognitive adaptive test and clinical linguistic auditory milestone scale (CAT/CLAMS).

Methods. In 48 of the original Tagum (T) subjects, cord blood and meconium Hg levels, head circumference (HC) at birth, and duration of breastfeeding were correlated with CAT/CLAMS at 2 years. At 2 years, THg levels using cold atomic vapor absorption spectrometry were determined in the hair of 46 T subjects and 88 Saranggani (S) controls; THg levels in blood were tested in 48 T subjects and 45 S controls. These levels were correlated with CAT/CLAMS. Both groups had standard physical and neurologic examinations, hearing screen using transitory evoked otoacoustic emissions, serum glutamate pyruvate transaminase, and routine urinalysis. A prevalidated Socioeconomic Means Test was given to both groups.

Results. The Hg level in cord blood was negatively correlated with CAT/CLAMS at 2 years. The HC at birth was negatively correlated with levels of Hg in hair of T subjects 2 years later. HC at birth and 2 years hence were positively correlated with CAT/CLAMS. The following were significantly higher in S controls than in T subjects: expressive language quotient 82.569 ± 2.21 versus 71.57 ± 2.61; CLAMS 87.96 ± 2.43 versus 77.67 ± 2.51; CAT 90.57 ± 2.22 versus 83.15 ± 1.43; and full-scale developmental quotient 89.31 ± 2.14 versus 80.56 ± 1.86. Fifteen percent of T subjects had global delay (full-scale developmental quotient <=70) versus 5.48% in S controls. Hg levels in hair and blood in both T subjects and S controls at 2 years showed no correlation with CAT/CLAMS. The duration of breastfeeding in both groups likewise showed no correlations with CAT/CLAMS.

Conclusion. The study suggests that prenatal Hg exposure is correlated with lower scores in neurodevelopmental screening, but more so in the linguistic pathway. Other confounding factors cannot be eliminated.

Key Words: prenatal hg exposure • developmental follow-up

Abbreviations: Hg, mercury • MeHg, methyl mercury • THg, total mercury • ppm, parts per million • ppb, parts per billion • HC, head circumference • T, Tagum • S, Saranggani • CAT, cognitive adaptive test • CLAMS, clinical linguistic auditory milestone scale • DQ, developmental quotient • SGPT, serum glutamate pyruvate transaminase • ELQ, expressive language quotient • RLQ, receptive language quotient • FSDQ, full-scale developmental quotient

Received for publication Nov 8, 2002; Accepted Aug 30, 2002.