Lead levels in teeth as a measure of life-time lead exposure in children

Abstract

Background and aims Lead exposure has irreversible health effects in children who are susceptible even at very low levels of exposure. The usual test for lead exposure is blood lead level (BLL), but this indicates only recent exposure. This study aimed to ascertain the suitability of milk teeth as biomarker of the history of lead exposure and to develop a methodology for this novel biomarker. Methods My study comprised three stages: Firstly, I explored potential determinants of dentine lead levels (DLLs) in children living in Newcastle upon Tyne (the Tooth Fairy Study). Secondly, I developed a methodology for assessing the history of early life lead exposure using dentine, and thirdly I applied my methodology to newly extracted teeth from children in Teesside. The Tooth Fairy study cohort consisted of 69 children aged 5-8 years. DLLs were measured in primary dentine using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). To identify determinants of early life exposure, a questionnaire was used. I assessed associations between lifestyle characteristics and DLLs. As teeth develop chronologically they offer the opportunity to study histories of exposure in detail. I collected two deciduous molars each from 15 children aged 6-8 years living in Northeast England. By combining high spatial resolution LA-ICP-MS with dental histology, I acquired information on the age specific concentrations of lead in dentine from in utero to several years after birth. Results Dentine lead levels in the Tooth Fairy cohort ranged from 0.06 to 0.77μg/g, median 0.21μg/g. Unlike other studies, I did not find significant associations between socio-economic status or other possible determinants and lead exposure. In developing the biomarker I found that the 100 micron ablation pit represented 42 days of dentine growth, enabling me to assign an age interval to each ablation pit. I found lead ratios in primary dentine to be consistent between teeth from the same child, and at the same age within each tooth. This indicated that the history of exposure can be determined using a single, multi-point ablation transect on high quality longitudinal sections of individual teeth. Conclusions  I found no association between socio-economic status and dentine lead levels in a cohort of children from Newcastle upon Tyne.  I developed a novel technique to date ablation points in dentine in milk teeth, and, using this technique have demonstrated that primary dentine is a potential biomarker for characterising the early life history of lead exposure in children.