Analytical Methods and Concentrations of Exposure Biomarker Chemicals in Deciduous Teeth, 01-R8235
Principal Investigators
David E. Camann
Alice Y. Yau
Inclusive Dates: 06/27/11 – 10/27/11
Background — Recent prospective cohort studies suggest that chemical exposures in the prenatal period and first year after birth have a greater adverse affect on a child's neurodevelopment, IQ and behavior. However, no methods currently exist to objectively measure exposures that a child received before birth and during specific intervals in early life to most medications, environmental chemicals and nutrients. The chemical and its metabolite measured in urine generally reflects exposure within 24 hours, while levels in hair reflects exposure in recent months and concentration in blood cannot be related to any specific past time point. A biomarker technique that documents exposure at a specific time during early development would greatly facilitate epidemiologic case-control studies of childhood diseases/conditions such as autism, attention deficit hyperactivity disorder, asthma, leukemia and obesity.
Approach — Each deciduous (baby) tooth can accumulate medications, environmental chemicals and nutrients from the bloodstream during its formation period. Each tooth has a specific period from initial formation through crown completion. This period can span from the 14th week in utero to age 1.5 months for upper central incisors and from the 19th week in utero to age 11 months for upper second molars. SwRI's approach is to develop methods to prepare and analyze exfoliated deciduous teeth for potential exposure biomarker chemicals, medications and nutrients, and to determine whether the level of a chemical or its metabolite in a tooth correlates with previously measured perinatal exposure, and could thus serve as a reliable biomarker of that exposure. A sample of pulled and shed deciduous teeth was chosen from 21 children in the general population to determine the detection frequency and the distribution of concentrations of the potential exposure biomarker chemicals.
Accomplishments — Tooth preparation, extraction, and analytical methods were developed for a broad spectrum of chemicals, medications and nutrients. Acetaminophen, anandamide, arachidonylglycerol, specific and non-specific metabolites of chlorpyrifos and diazinon, and monoethylhexyl phthalate were analyzed by tandem liquid chromatography/mass spectrometry and polyunsaturated fatty acids and pesticides by gas chromatography/mass spectrometry. The metal mercury was analyzed by cold vapor atomic absorption. Concentrations of most of these chemicals were determined in 35 deciduous molars. SwRI is teaming with The University of Texas Health Science Center at San Antonio in a grant application to NIH to measure these chemicals in 400 deciduous teeth as part of a study to investigate autism risk using tooth measurements to assess early life exposure.
