New research by North­eastern Uni­ver­sity pro­fessor Richard Deth and aca­d­emic col­leagues in Ger­many sug­gests that long-​​term expo­sure to mer­cury may pro­duce Alzheimer’s-like symp­toms in people.

Deth also dis­cov­ered a prob­able bio­log­ical mech­a­nism through which mer­cury can destroy neu­ro­log­ical brain func­tion in humans.

The find­ings were reported this month in a study pub­lished in the Journal of Alzheimer’s Disease.

The team of researchers con­ducted a lit­er­a­ture review of more than 100 exper­i­mental and clin­ical studies on mer­cury expo­sure in cell models, ani­mals and humans. They found that ani­mals exposed to mer­cury exhib­ited many of the patho­log­ical changes asso­ci­ated with the Alzheimer’s dis­ease, including memory loss, poor cog­ni­tive per­for­mance and confusion.

The researchers don’t have enough evi­dence to con­clude that mer­cury expo­sure def­i­nitely causes these symp­toms in humans, but data indi­cates a need to restrict expo­sure as a pre­cau­tionary measure.

Mer­cury is clearly con­tributing to neu­ro­log­ical prob­lems, whose rate is increasing in par­allel with rising levels of mer­cury,” said Deth, a pro­fessor of phar­ma­cology in the Bouvé Col­lege of Health Sci­ences. “It seems that the two are tied together.”

Mer­cury, one of the most toxic nat­ural sub­stances, is found in some species of food fish, in amalgam dental fill­ings and in energy-​​saving flu­o­res­cent light bulbs. Mer­cury emis­sions from coal-​​burning power plants enter the food chain.

The heavy metal evap­o­rates at room tem­per­a­ture, turns into a gas, enters the body, crosses the blood-​​brain bar­rier and gets trapped inside the brain, where it accu­mu­lates over time.

Deth found that mer­cury expo­sure impairs cog­ni­tive func­tion by reducing the effi­cacy of sele­nium, an antiox­i­dant that helps keep the brain healthy by sup­pressing dam­aging chem­ical reac­tions in humans.

Mer­cury binds to sele­nium, said Deth, pro­moting “oxida­tive stress” and decreasing the amount of avail­able antiox­i­dants. Nerves stop func­tioning nor­mally, cog­ni­tive impair­ment sets in and cells die.

Deth’s coau­thors on the paper, titled “Does Inor­ganic Mer­cury Play a Role in Alzheimer’s Dis­ease? A Sys­tem­atic Review and an Inte­grated Mol­e­c­ular Mech­a­nism,” include col­leagues from the Insti­tute of Tran­scul­tural Health Studies, at the Euro­pean Uni­ver­sity Viad­rina, the Euro­pean Office of the Samueli Insti­tute, and the Depart­ment of Envi­ron­mental and Inte­gra­tive Med­i­cine, Kon­stanz, all in Germany.