Childhood Lead Exposure Map: MNPH Data Access

There is no safe level of lead exposure. Even low levels of lead exposure can harm a child.

“Percent elevated” describes the proportion of children with an elevated blood lead level (5+ mcg/dL) among children tested. Because lead testing was not universal in Minnesota until 2022, the “percent elevated” indicator cannot be generalized for the overall population of children living in Minnesota.

This map uses an annual (test year) approach, to determine how many children tested in a 5-year period had an elevated blood lead level. The population includes all children who were tested at least once between January 1, 2017, and December 31, 2021, and were under 6 years of age at the time of the test. Each child could contribute only 1 EBLL in this 5-year time period.

Lead testing was not universal in Minnesota until 2022. Minnesota guidelines did not recommend universal screening for childhood lead exposure until 2022. In the data shown here, lead testing was targeted for children with risk factors for lead exposure.

The Centers for Disease Control and Prevention (CDC) updated their reference level from 5 micrograms per deciliter (5 mcg/dL) to 3.5 mcg/dL in 2021 to identify children with blood lead levels that are much higher than most children’s levels. This new reference level is based on the U.S. population of children one to five years old who are in the highest 2.5% of children when tested for lead in their blood, based on the National Health and Nutrition Examination Survey (NHANES) data. Reference levels are expected to decline over time as blood lead levels in U.S. children decline.

By combining 5 years of blood lead surveillance data in this map, we are able to display data using a small geographic unit (census tract) while still protecting data privacy and ensuring estimate precision. The statewide prevalence of children with elevated blood lead levels declined throughout this time period. Caution should be used when comparing single-year estimates to 5-year estimates.

Geographies mapped here are census tracts as determined from the 2010 U.S. Census Bureau. Typically, about 90-95% of children with a blood lead test result in Minnesota were are successfully geocoded to a census tract by the child’s residential address. That means that the number of EBLLs in each census tract could be a slight underestimate. Some children’s addresses may not be geocoded if they are non-residential addresses, such as: P.O. boxes, partial addresses like when the directional indicator (N, W, etc.) is left off an address, or data entry errors. The proportion of children with a geocoded address (and included in this map) does not significantly differ between children with an EBLL and children without an EBLL, indicating the prevalence estimates are not biased by the geocoding process. However, the census tract of residence is not always the location where the child was exposed to lead. Children with blood lead test results that could not be geocoded are included in the county and Minnesota totals.”

Census tracts are small, relatively permanent geographies that are smaller than counties, larger than census block groups, and roughly equivalent to a neighborhood. Census tracts generally have a population between 1,200 and 8,000 people, with an optimum size of 4,000 people.

County name in hover-over window is the primary county of that census tract, as assigned by the U.S. Census Bureau. Some census tracts may extend into another Minnesota county.

Map categories for the “percent elevated” indicator (the difference compared to Minnesota) were calculated by comparing the 95% confidence interval of “percent elevated” in each census tract to the 95% confidence interval for “percent elevated” statewide. Using difference from the mean methodology, census tracts were then classified as significantly different from MN if the intervals do not overlap – either higher than the state mean (average) or lower than the state – or as no different from the state if intervals overlap. Geographies that were higher than the state mean (average) are classified as either 1-2 times higher, or 3 or more times higher. A geography has a rate more than 3 times that of the state if the lower bound of the tract’s 95% confidence interval is greater than three times the state point estimate.

The CDC and National Tracking Network define a confirmed elevated blood lead level as a single elevated venous test (from a vein) OR two elevated capillary tests (from a finger prick) within 12 weeks. However, Minnesota statute requires a venous test as confirmation before an environmental assessment is conducted. The Tracking definition of a confirmed test may include some cases that did not have venous confirmation. All data shown on the map use the Tracking definition of a confirmed elevated blood lead level.

Each child can only contribute one blood lead test result. If a child has multiple confirmed tests, only the highest confirmed test result is included in analyses.

The percent of EBLLs in each county is for comparison purposes, and includes children tested from 2017 to 2021 in each county.

To protect privacy, counts of 1 to 4 EBLLs are suppressed, and indicated by “*1-4” in the map. A range is provided for the percent of children with an EBLL when based on a count of 1-4.

Some census tracts did not have any children tested during this time period. These are displayed on the map as “no data available.” This could be because no children under 6 years of age living in that tract had received a blood lead test between 2017 to 2021. It’s also possible that there were children tested for blood lead in that area but they were not successfully geocoded to that tract.

For additional information, visit About the childhood lead exposure data.

About the Data

Table: Childhood Lead Exposure (2017-2021)

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