Exposure to harmful toxic metals in utero and during early life is a global health problem. Although millions of children worldwide are exposed to multiple metals at those times, we still lack convincing evidence of the impact of metal exposure, particularly mixtures of metals, on childhood lung function. Indeed, most studies investigated metals individually, but in real life, pregnant women and their children are exposed to many metals simultaneously, and their combined effects are often unpredictable. Because the human lung develops through a sequence of highly choreographed processes, ideally, human studies would continuously measure levels of multiple metals to identify relevant windows of susceptibility. In this study, we will obtain weekly measurements of multiple metal exposures simultaneously by using a highly innovative method to measure metal levels in deciduous teeth. Like trees, teeth develop in layers that trap metals at concentrations commensurate with exposure levels. Hence, each layer is like a time capsule that contains metal levels from the time it was formed. We will use a validated method to measure 14 metals in teeth. We can assess exposures cumulatively, as well as at discrete week-by-week developmental windows, starting prenatally as early as gestational weeks 13-16 up to the time of tooth collection (~6 years). In order to develop a noninvasive and inexpensive biomarker for later-life lung function, we will combine our analyses of these metal assessments in teeth with novel blood-based biomarkers that leverage the unique properties of the mitochondrial DNA (mtDNA), a cumulative biosensor of metal-induced oxidative DNA damage. Our goal is to use tooth-based, time-specific measures of metals to assess their effects on lung function individually or as a mixture. We hypothesize that metals adversely affect lung function and that the effects of metal exposures on children?s lungs are associated with the cumulative damage measured in blood mtDNA. We can time- and cost-effectively conduct this research by leveraging the infrastructure of the Health Effects of Arsenic Longitudinal Study (HEALS), a well-characterized prospective cohort of 35,000 adults and their children in Araihazar, Bangladesh. The proposed study will include 600 children ages 6-10 years. We will collect at least one deciduous tooth sample from each child and conduct standard lung function tests and obtain blood mtDNA measures twice, 2 years apart. We anticipate that findings from this innovative and cost-efficient study will generate information on the impact of in utero and early-life exposure to multiple metals on pulmonary function in children. Information generated from this study will appreciably improve our understanding of lung function in response to environmental metal exposure and ultimately will inform strategies to improve lung function in children.
Our research will use an advanced tooth biomarker approach to determine 1) accurate timing of exposure to 14 metals?separately and as mixtures, and 2) their developmental windows of susceptibility for lower lung function in late childhood. We will also use blood mitochondrial DNA measures to identify simple and inexpensive biomarkers that reflect cumulative biological effects of earlier exposure to metals and predict children?s lung function specific to metal toxicity. Our research has enormous implications for future research, interventions, and public health policy and will create a model that can be extended to identify additional risk factors for lung diseases, as well as for many other disorders aggravated by environmental pollutants.
