Manganese is an
element essential for health in trace amounts, but toxic at higher exposures. Since
manganese is replacing lead in
gasoline globally, evaluation of potential
cancer effects is essential. To determine whether environmental
manganese is related to
cancer at the county level in North Carolina (n = 100 counties; North Carolina 2000 population = 8,049,313), we carried out an ecological study using data from the North Carolina State Center for Health Statistics, North Carolina Geological Survey, US Geological Survey, and US Census. County-level all-cause and
cancer mortality rates between 1997 and 2001 reported in deaths per 100,000 population associated by multivariable regression with logarithmically transformed groundwater (microgram per liter) and airborne (microgram per cubic meter)
manganese concentrations by county measured between 1973 and 1979 (water) and in 1996 (air). Models controlled for county characteristics. Median all-cause and
cancer mortality rates by county in North Carolina (1997-2001) exceeded those of the USA (2000). For each log increase in groundwater
manganese concentration, there was a corresponding county-level increase of 12.10 deaths/100,000 population in all-site
cancer rates, 2.84 deaths/100,000 in
colon cancer rates, and 7.73 deaths/100,000 in
lung cancer rates. For each log increase in airborne
manganese concentration, there was a corresponding county-level decrease of 8.10 deaths/100,000 population in all-site
cancer rates, 3.28 deaths/100,000 in
breast cancer rates, and 3.97 deaths/100,000 in
lung cancer rates. Neither groundwater nor air concentrations of
manganese correlated with county-level all-cause or
prostate cancer death rates. These are the first data we know of to document a potential relationship between environmental
manganese and population-level
cancer death rates. The positive association between groundwater
manganese and specific
cancer mortality rates might be a function of the high concentrations measured, while the inverse relationship between air
manganese and death rates might point toward adequate (e.g., healthy) county-level
manganese exposures. Since
manganese is replacing lead in
gasoline globally, these ecological findings should be confirmed at the individual level or in animal models.