But a new federal standard challenges Minnesota to reduce levels in thousands more.
Minnesota has substantially cut the number of children with unhealthy lead levels, but a new safety limit for the toxic metal means the state has more work to do.
The number of children with "elevated" levels -- at least 10 micrograms of lead per deciliter of blood -- dropped from 4,339 in 1995 to 584 last year, according to state Department of Health figures released Wednesday.
Trouble is, federal authorities determined this year that a lead level of 5 or higher should be the new threshold for concern. And testing in Minnesota identified more than 3,000 children with lead levels at least that high.
The decline in children with elevated lead levels under the old standard is still meaningful because the toxic impact of lead -- which can include brain and nerve damage -- generally gets worse when the lead levels are higher, said Dan Symonik, a supervisor in the state Health Department's lead and healthy homes program.
"Like any toxin, as the dose gets higher the things that it causes get worse," Symonik said. "At the higher levels you have behavior issues and long-term mental issues, those kinds of things. At the lower levels ... the effects are much more subtle, but they can be significant."
The number of blood tests for lead exposure, primarily of children younger than 6, has tripled in Minnesota over the past two decades, making the drop in "elevated" cases even more significant.
Lead exposure is particularly common for children living in older homes, because a government ban on lead-based house paint didn't take effect until the late 1970s. About three-fourths of Minnesota's houses were built before 1978, officials said Wednesday. Contaminated water supplies from lead pipes can be a source as well.
Public health nurses used to visit homes of children with elevated lead levels under the old definition, but now they are using the new standard and visiting homes of children whose lead levels are 5 or higher.
The change has created staffing pressures for state and county health departments, at a time when federal funding for lead prevention workers was cut, Symonik said. Responders also find it harder to identify the sources of lead exposure in lower-level cases. Often, the sources in those cases are varied.
Minnesota still uses an old threshold of 15 micrograms per deciliter before requiring homeowners or landlords to eliminate known sources of lead exposure in buildings. In cases where children have lower levels, public health officials merely provide advice to families on how to eliminate lead.