Associations Between Metal Exposure and Infants’ Developmental Growth Across 2 and 12 Months

• In Event: 3-064 - The Effects of Environmental Toxicity on Neurodevelopmental Outcomes Across Infancy and Early Childhood

Integrative Statement

Prenatal exposure to heavy metals/metalloids and its effects on infant health and development is a growing public health concern in the United States, and especially relevant in the Navajo Nation. Located in the southwest region of the U. S., a legacy of more than 500 abandoned uranium mines remain from the Cold War era and pose serious risks for exposure to a wide range of co-located heavy metals and metalloids. The current study examined the associations between concentrations of heavy metals and metalloids in mothers’ prenatal biospecimens and subsequent infants’ neurodevelopmental trajectories between ages 2 and 12 months in five domains as measured by the Ages & Stages Questionnaire Inventory (ASQ:I). Specifically, heavy metal/metalloid concentrations in maternal prenatal biospecimens were expected to predict decreased infant neurodevelopmental scores at age 2 months and flatter trajectories between ages 2 and 12 months.
Pregnant Navajo women receiving prenatal health care services from clinics throughout Navajo Nation were recruited to participate in the Navajo Birth Cohort Study (NBCS). Participating mothers (N = 535) completed a range of assessments during the prenatal period including blood and urine specimen collection at enrollment and delivery. In addition to maternal biomonitoring, infants’ development across five major domains were measured (i.e., communication, fine and gross motor skills, problem solving, and personal-social skills) using the Ages & Stages Questionnaire Inventory (ASQ:I), which is a screening tool developed for monitoring and evaluating children’s development across 1 to 36 months. The ASQI was administered when infants were approximately 2, 6, 9, and 12 months of age.
Data analyses were conducted to estimate the association between concentrations of heavy metals/metalloids in maternal prenatal biospecimens and rates of change in the five ASQ-I domains. Rates of change in ASQ:I domain scores were estimated using longitudinal growth trajectory models. Maternal prenatal metal/metalloid concentrations were modeled as predictors of ASQ-I domain scores at 2-months as well as rates of change in ASQ:I domain scores between 2 and 6 months and between 6 and 12 months.
Significant negative effects were obtained for a range of maternal biospecimen metal/metalloid concentrations and infant neurodevelopmental trajectories as measured by the ASQ:I. The adverse effects of maternal prenatal heavy metal exposure on infant neurodevelopment were primarily evident between ages 6 and 12 months, and relatively few effects were observed prior to age 6-month. Specifically, between 6 and 12 months of age rates of change in ASQ-I domain scores were inversely related to maternal prenatal biospecimen concentrations of antimony, barium, cadmium, lead, manganese, uranium, and zinc. These inverse relationships were most frequent for the domains of communication, personal-social functioning, and fine motor skills. While these analyses considered the effects of individual metals as a starting point, Bayesian clustering results on metal exposure patterns indicate that ~25% of mothers in the cohort are in a cluster defined by exposure to the upper quantile of all metals in this list, with the exception of zinc. Ongoing analyses continue to probe these exposure mixtures, as well as other risk variables to refine our understanding of these early neurodevelopmental trajectories as the result of risk factors.

Group Authors

The Navajo Birth Cohort Study Team

Authors

• Sara S. Nozadi, University of New Mexico, Community Environmental Health Program
  Non-Presenting Author

• Brandon Rennie, University of New Mexico, Department of Pediatrics, Center for Development and Disability
  Presenting Author

• Li Li, University of New Mexico, Department of Math and Statistics
  Presenting Author

• Timothy Ozechowski, University of New Mexico, Department of Pediatrics
  Non-Presenting Author

• Ruofei Du, University of New Mexico, Comprehensive Cancer Center
  Non-Presenting Author

• Jospeh Hoover, University of New Mexcio, Community Environmental Health Program
  Presenting Author

• Navajo Birth Cohort Study Team, University of New Mexcio, Community Environmental Health Program, Southwest Research and Information Center, Navajo Nation Department of Health
  Non-Presenting Author

• Johnnye L Lewis, University of New Mexcio, Community Environmental Health Program
  Non-Presenting Author