Groundwater manganese and infant mortality rate by county in North Carolina: an ecological analysis

Manganese is an element essential in trace quantities but toxic in high concentrations. As a naturally occurring element in groundwater and a chemical of increasing global significance due to its growing trend of replacing lead in gasoline, vigilant assessment of its detrimental effects is essential. In response to previous research that showed a potential link between manganese and well water, we performed a pilot ecological study using data obtained from the North Carolina Center for Health Statistics, the North Carolina Geological Survey, and the U.S. Census. Our pilot study investigated the relationship between logarithmically transformed county level groundwater manganese concentrations with county level infant mortality rates (reported as deaths/1,000) within the state of North Carolina (n = 100 counties; North Carolina 2000 population = 8,049,313) using stepwise, multiple regression. Our model accounted for such confounders as low birth weight, economic status, education, and ethnicity. Across North Carolina counties, for every log increase in groundwater manganese concentration, there was a 2.074 increase in county level infant deaths per 1,000 live births. This study is the first to show on a statewide basis adverse infant mortality effects of environmental manganese. These pilot data argue for further research into a broad range of developmental effects and also may be useful to regulatory agencies interested in protecting communities' health.