Prenatal exposure to dental amalgam in the Seychelles Child Development Nutrition Study: associations with neurodevelopmental outcomes at 9 and 30 months.
BACKGROUND
Dental amalgam is approximately 50% metallic mercury and releases mercury vapor into the oral cavity, where it is inhaled and absorbed. Maternal amalgams expose the developing fetus to mercury vapor. Mercury vapor can be toxic, but uncertainty remains whether prenatal amalgam exposure is associated with neurodevelopmental consequences in offspring.


OBJECTIVE
To determine if prenatal mercury vapor exposure from maternal dental amalgam is associated with adverse effects to cognition and development in children.


METHODS
We prospectively determined dental amalgam status in a cohort of 300 pregnant women recruited in 2001 in the Republic of Seychelles to study the risks and benefits of fish consumption. The primary exposure measure was maternal amalgam surfaces present during gestation. Maternal occlusal points were a secondary measure. Outcomes were the child's mental (MDI) and psychomotor (PDI) developmental indices of the Bayley Scales of Infant Development-II (BSID-II) administered at 9 and 30 months. Complete exposure, outcome, and covariate data were available on a subset of 242 mother-child pairs.


RESULTS
The number of amalgam surfaces was not significantly (p>0.05) associated with either PDI or MDI scores. Similarly, secondary analysis with occlusal points showed no effect on the PDI or MDI scores for boys and girls combined. However, secondary analysis of the 9-month MDI was suggestive of an adverse association present only in girls.


CONCLUSIONS
We found no evidence of an association between our primary exposure metric, amalgam surfaces, and neurodevelopmental endpoints. Secondary analyses using occlusal points supported these findings, but suggested the possibility of an adverse association with the MDI for girls at 9 months. Given the continued widespread use of dental amalgam, we believe additional prospective studies to clarify this issue are a priority.
Eastman Institute for Oral Health, and Department of Pharmacology and Physiology, University of Rochester, 601 Elmwood Avenue, Box 705, Rochester, NY 14642, USA; Department of Environmental Medicine, University of Rochester, 601 Elmwood Avenue, Box EHSC, Rochester, NY 14642, USA. Electronic address: gene_watson@urmc.rochester.edu.
Gene E
GE
Watson
Department of Biostatistics and Computational Biology, University of Rochester, 601 Elmwood Avenue, Box 630, Rochester, NY 14642, USA.
Katie
K
Evans
Department of Biostatistics and Computational Biology, University of Rochester, 601 Elmwood Avenue, Box 630, Rochester, NY 14642, USA.
Sally W
SW
Thurston
Department of Community and Preventive Medicine, University of Rochester, 265 Crittenden Blvd., CU 420644, Rochester, NY 14642, USA.
Edwin
E
van Wijngaarden
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
Julie M W
JMW
Wallace
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
Emeir M
EM
McSorley
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
Maxine P
MP
Bonham
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
Maria S
MS
Mulhern
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
Alison J
AJ
McAfee
Department of Environmental Medicine, University of Rochester, 601 Elmwood Avenue, Box EHSC, Rochester, NY 14642, USA; Department of Pediatrics, University of Rochester, 265 Crittenden Blvd., CU 420606, Rochester, NY 14642, USA.
Philip W
PW
Davidson
Republic of Seychelles Ministry of Health and Social Services, Victoria, Mahé, Seychelles.
Conrad F
CF
Shamlaye
Northern Ireland Centre for Food and Health (NICHE), University of Ulster, Cromore Road, Coleraine BT52 1SA, Northern Ireland.
J J
JJ
Strain
Department of Biostatistics and Computational Biology, University of Rochester, 601 Elmwood Avenue, Box 630, Rochester, NY 14642, USA.
Tanzy
T
Love
Department of Environmental Medicine, University of Rochester, 601 Elmwood Avenue, Box EHSC, Rochester, NY 14642, USA.
Grazyna
G
Zareba
Department of Environmental Medicine, University of Rochester, 601 Elmwood Avenue, Box EHSC, Rochester, NY 14642, USA; Department of Pediatrics, University of Rochester, 265 Crittenden Blvd., CU 420606, Rochester, NY 14642, USA; Department of Neurology, University of Rochester, 601 Elmwood Avenue, Box 631, Rochester, NY 14642, USA.
Gary J
GJ
Myers
D000367:Age Factors; D002657:Child Development / Q000187:drug effects*; D002675:Child, Preschool; D003071:Cognition / Q000187:drug effects; D003723:Dental Amalgam / Q000009:adverse effects*; D005260:Female; D005506:Food Contamination; D006801:Humans; D007223:Infant; D007361:Intelligence Tests; D016014:Linear Models; D008297:Male; D018811:Maternal Exposure / Q000009:adverse effects*; D020262:Mercury Poisoning, Nervous System / Q000209:etiology* / Q000503:physiopathology / Q000523:psychology; D008767:Methylmercury Compounds / Q000009:adverse effects; D009048:Motor Skills / Q000187:drug effects; D009420:Nervous System / Q000187:drug effects* / Q000254:growth & development / Q000503:physiopathology; D009483:Neuropsychological Tests; D009749:Nutrition Surveys; D011247:Pregnancy; D011297:Prenatal Exposure Delayed Effects; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D017747:Seafood / Q000009:adverse effects; D012737:Sex Factors; D012750:Seychelles; D014835:Volatilization; D014874:Water Pollutants, Chemical / Q000009:adverse effects
D008767:Methylmercury Compounds; D014874:Water Pollutants, Chemical; D003723:Dental Amalgam