Asking people to monitor their fish intake is not enough to control mercury poisoning in individuals, a recent study suggests.

The study, conducted by the Harvard University School of Public Health, concluded that of the 172 people who live around the Lafarge cement plant in Ravena, New York, nearly one person in 10 had elevated mercury levels in their blood high enough to merit a doctor's visit. Michael Bank, the researcher who led the study, said that consumption of fish accounts for only about 15 percent of elevated mercury cases in adults in Ravena, and about 50 percent of such cases in children.

Community Advocates for Safe Emissions (CASE), a grassroots advocacy group that has been pushing for tougher controls on mercury pollution from the Lafarge plant, initiated the study.

Lafarge is New York's second-largest emitter of airborne mercury, releasing approximately 167 pounds of the toxin into the air every year, according to a 2009 state estimate. Mercury is a potent neurotoxin that can cause developmental problems in children and developing fetuses. It accumulates in the body over time, which is why adults in the Ravena study had far higher mercury levels than children.

According to the United States Centers for Disease Control's (CDC) National Health and Nutrition Examination Survey, elevated mercury levels are considered to be five parts per billion or higher. That level was found in 10 percent of the Ravena study population, even in those who did not eat local fish.

CASE co-founder Elyse Kunz said, "The study is significant, and raises a lot of questions. It begs what the state Health Department has been telling us, that there was no problem if people were not eating the fish."

Let's ask New York's Health Department to sponsor more research into the deleterious effects of airborne mercury, because contaminated fish are not the only danger to ourselves and our children. This important study shows that there is a problem, but "does not say where the mercury is coming from," according to Kunz, and we need to know to protect ourselves.