A new study, published in the journal NeuroToxicology, shows that children who test higher for levels of manganese (Mn) in their hair tend to have significantly lower IQ scores.
Manganese, a trace mineral, is nutritionally essential to humans but toxic when ingested in high amounts. Manganese is used widely in the production of steel, alloys, batteries, and fertilizers and is added to unleaded gasoline.
For the study, environmental health researchers at the University of Cincinnati (UC) College of Medicine analyzed blood and hair samples of 106 children seven to nine years of age living in and around the city of East Liverpool, Ohio. East Liverpool has a demonstrated history of environmental exposures, with EPA records showing elevated levels of manganese concentrations since 2000.
Working with a trained registered nurse from East Liverpool, participants and their caregivers underwent cognitive assessments and completed questionnaires at the time the samples were taken. The findings show that increased Mn in hair samples was significantly associated with declines in full-scale IQ, processing speed, and working memory.
Manganese is an element generally found in combination with iron and many minerals. It plays a vital role in brain growth and development, but excessive exposure can result in neurotoxicity.
Erin Haynes, Dr.P.H., associate professor in the Department of Environmental Health and lead author of the study, was approached by East Liverpool school district officials in 2013, prompted by concerns of students’ academic performance, paired with the knowledge that Mn concentrations in the area have exceeded U.S. Environmental Protection Agency (EPA) reference levels for more than a decade.
“There are socioeconomic issues at play, however, they are also compounded by potentially significant environmental exposures,” said Haynes, who collaborated with the Kent State East Liverpool Campus and the community group Save our County Inc., formed in 1982 by East Liverpool residents in response to the proposed construction of a hazardous waste incinerator in their community.
“Children may be particularly susceptible to the neurotoxic effects of ambient Mn exposure, as their brains are undergoing a dynamic process of growth and development.”
After concerns of elevated airborne levels of Mn, the school district superintendent in East Liverpool requested testing students for manganese along with neuropsychological tests.
A pilot study found levels of Mn at double the level in children from the other CARES study cohort, and further investigation was pursued to examine the relationship between Mn exposure and child cognition.
In 2005, East Liverpool was deemed by the EPA to be a potential environmental justice area, afflicted with major environmental exposures. In addition, a 2010 EPA report noted manganese concentrations detected by all monitors in East Liverpool had “consistently exceeded” health-based guidelines set by the agency.
With a declining population of only 11,000 residents, just 7.3 percent of those living in the city have a college degree. The East Liverpool school district reports a higher than average percentage of students in special education (19 percent) versus the Ohio state average of 13 percent.
The school board learned of Haynes’ manganese studies in Marietta, Ohio. Marietta was the original location of the Communities Actively Researching Exposure Study (CARES), initiated in 2008 based on community concern about exposure to manganese from a nearby metallurgical manufacturing company.
Marietta and East Liverpool have some of the highest levels of ambient manganese in the country, Haynes says, and notes that their studies continue in these areas and include neuroimaging, “as we continue to advance our understanding of the impact of manganese on neurodevelopment, and help to define the lines between essential benefit and toxicological harm.”