Chicago's Department of Public Health announced Friday that it will conduct a study of Hispanic households that have been exposed to mercury during religious rituals or while practicing folk medicine.

Beads of mercury--the silvery liquid metal that is toxic when inhaled or ingested--can be purchased legally in Chicago at alternative medicine shops called botanicas. The droplets are believed to ward off evil or have healing powers, and they are common to faiths such as Santeria, the West African belief system that took root in the Caribbean.

Following in the wake of the possible contamination of thousands of homes by mercury from old gas meters, health officials held a press conference Friday to bring attention to their plans to study the ritualistic use of mercury.

"What we want to find out is, is this a large-scale problem or not?" said Dr. Daniel Hryhorczuk, director of the Cook County Hospital's Center for Children's Environmental Health, who was joined by the director of the Health Department's Office of Hispanic Affairs.

Researchers hope to involve 100 people in 25 to 40 homes, he said. Both the homes and people would be tested for exposure.

A 1997 University of Illinois at Chicago survey found 16 botanicas selling mercury --and only four of them had properly labeled the substance as dangerous. Mercury can be bought in vials, amulets or capsules, and it is sometimes sprinkled throughout homes, burned in candles or ingested.

Though it is used in folk medicine to combat ailments such as stomachaches, alcoholism or even nervousness, Hryhorczuk said the elemental metal is hazardous and has no proven health benefits. It can inhibit brain function and development, cause mental retardation or, in extreme cases, death.