A study published in the Journal of Neuroscience last week reports a link between lead exposure and accumulation of Alzheimer’s-type plaque in the brains of primates. The National Institutes of Health-funded study examined the brain tissues of 23-year-old monkeys that had been exposed to lead for the first 400 days of their lives (resulting in blood lead levels of 19–26 µg/dl, but no overt signs of toxicity), and found that they had elevated expression of Alzheimer’s-related genes as well as altered levels, characteristics, and distribution of amyloid plaques, which are one of the hallmarks of Alzheimer’s Disease.

The study’s lead researcher, Dr. Nasser Zawia of the University of Rhode Island, told the Providence Journal that the research is significant because, while he’s found similar results in mice and rats, this is the first time scientists have found the lead-Alzheimer’s link in primates. Zawia and a spokesperson for the Alzheimer’s Association put the results in context for people worried about their own disease risk:

Zawia and a spokesman for the national Alzheimer’s Association cautioned that the study should not prompt lead-poisoning victims or their families to fear that their lead exposure will automatically lead to Alzheimer’s.

Until the last few years, Rhode Island has been a hot bed of lead poisoning. More than 30,000 children have been diagnosed with elevated lead levels since 1991.

“I would say it’s just another factor, another risk factor,” Zawia said in a telephone interview. “It’s like how smoking is a risk factor for cancer. It puts you at greater risk. But there are 100 other things that can intervene between early life and old age. And this does not just apply to lead. Certain other things may lay dormant for many years.”

William H. Thies, vice president of medical and scientific relations at the Alzheimer’s Association in Chicago, called the study “good, solid basic science,” but he also emphasized “making a leap from this paper to saying Alzheimer’s disease is caused by early childhood lead exposures doesn’t fit.”

Thies recalled that in the past some people pinpointed aluminum as a cause of Alzheimer’s and many people threw away their aluminum pots and pans before that theory was rejected.

“I predict we’ll find no single, monolithic cause,” said Thies. “We know there are already lots of good reasons for removing lead from the environment. And it’s certainly possible lead is a contributor to Alzheimer’s. But I don’t think it’s the answer to solving Alzheimer’s.”

Since we already know that lead poisoning causes serious neurological problems in children – and that even elevated blood-lead levels below the official cutoff are cause for concern – health officials are already motivated to reduce lead exposure, and this finding may not have much effect on prevention efforts. It’s an important reminder, though, that the substances we’re putting in our environment today might have health effects that won’t become apparent until decades into the future.