About Lead Poisoning Data

about lead poisoning

The Tracking Network uses data collected by the IDPH Lead Poisoning Prevention program. Since 1992, the IDPH has required that the results of all blood lead testing done on Iowa residents be reported to the lead poisoning prevention program.

This page provides general information about lead data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us?

  • The number and percent of children tested for blood lead prior to either 3 or 6 years of age in Iowa, either by test year - the year that the blood test was performed (annual method) - or by birth year (cohort method).
  • Among children who were tested, the number and percent of children with elevated blood lead levels in the state of Iowa, by two different methods: birth year (cohort method) and test year (annual method).
  • The geographic distribution of testing rates, elevated blood lead levels, and risk factors for elevated blood lead levels in children, including residing in housing built prior to 1978 (and especially pre-1950 housing), and living in poverty.

Back to top

How can we use these data?

  • To inform the public about testing coverage for blood lead levels in children, elevated blood lead levels, and the geographic distribution of associated risk factors for elevated blood levels.
  • For program planning and evaluation by state and local partners

Back to top

What can these data not tell us?

  • Results are representative of children living in Iowa because blood lead testing is universal, all children are required to have at least 1 test before kindergarten. Statewide, about 85% of children are tested for blood lead by the time they reach 3 years of age, and only about 25% of children under 6 years of age are tested each year.
  • Data cannot tell us exactly how or where a child was exposed to lead.

Back to top

What are the sources of the data?

  • Data on blood lead testing and elevated blood lead levels are provided by the Iowa Department of Public Health which implements the Childhood Lead Poisoning Prevention Program (CLPPP), and are extracted from the Healthy Homes and Lead Poisoning Surveillance System (HHLPSS)
  • Data on the geographic distribution of housing age and poverty are taken from the most recent American Community Survey (ACS) 5-year estimates.

Back to top

What time period of data is available?

  • The Iowa Public Health Tracking portal displays lead testing data from the year 2000 through the most recent year of data available.
  • The Iowa Public Health Tracking portal displays ACS data from the year 2009 through the most recent year of data available.
  • There is usually a 6-month lag period before lead data are available.

Back to top

How are elevated blood lead levels (EBLLs) defined?

  • On October 28, 2021, CDC updated the blood lead reference value (BLRV) from 5.0 μg/dL to 3.5 μg/dL. A BLRV is intended to identify children with higher levels of lead in their blood compared with levels in most children. The value is based on the 97.5th percentile of the blood lead distribution in U.S. children ages 1–5 years.
  • The National Tracking Network defines a “confirmed” elevated blood lead level as one "venous" test result greater than or equal to 10 mcg/dL, or two "capillary" test results greater than or equal to 10 mcg/dL within 12 weeks of each other.
    • Capillary blood specimens are drawn from a finger stick, and the blood is collected either in capillary tubes or on filter paper. These specimens are considered "screening" tests because they are prone to falsely high results because of surface contamination when children's hands are not properly washed (prior to drawing the blood). Capillary tests, however, tend to be more acceptable to parents and may be performed in a wider range of settings (i.e., outside of clinical settings).
    • Venous specimens are considered "diagnostic" tests because they are drawn directly from a vein, but they may be less acceptable to some parents because of a child's discomfort. These tests also require greater expertise in drawing the blood.
  • If a child has multiple confirmed tests, only the highest confirmed test result is displayed. This applies to an individual test year or a birth year. However, children can appear in multiple test years using the annual method.

Back to top

What is the methodology used for the Lead Exposure Risk Model?

  • The Lead Exposure Risk Model is calculated using three different types of U.S. Census demographic data: 1) estimates of the number of housing units built prior to 1950, 2) estimates of the overall poverty rate of children under 6 years of age, and 3) estimates of the overall rate of households where English is not the main language spoken in the home. All input data is taken from the U.S. Census American Community Survey (ACS) five-year population estimates for census tracts in Iowa (B17001, B25034, & C16001 data files).
  • The Lead Exposure Risk Model was created by adding the risk of housing, poverty, and language spoken risk scores into high, medium, and low categories. The categorization was determined based on deciles and were assigned a 1, 2 or 3.
  • The high category contains the top 33.3% of the distribution; the low category contains the bottom 33.3% of the distribution; and the medium category contains the middle 33.4% of the distribution.

Back to top

What are the limitations of the data?

  • Blood lead testing is universal but not randomly sampled in Iowa, so the data collected by HHLPSS may not be representative of all Iowa children. The IDPH Childhood Blood Lead Screening Guidelines direct physicians to order blood lead tests for certain populations at higher risk for lead exposure.
  • The percent of children tested by birth year in a specific county can occasionally exceed 100%. This is because the percent of children tested is not calculated using the total number of children living in that county but, rather, is calculated using the total number of children born in a county in that birth year as a denominator. The number of children tested prior to 3 years of age in a specific county may be higher than the number of children that were born in that county.
  • American Community Survey (ACS) data on the proportion of older housing provides a population-based proxy for risk of lead exposure, especially housing built before 1950, because old properties with lead-based paint are the most common source of exposure. However, this measure may not accurately reflect exposure risk for several reasons:
    • ACS data are aggregated to county or census tract areas to provide population-level totals or percentages, so may not accurately reflect exposure risk for individual residents.
    • Residential addresses in HHLPSS may not reflect the actual location of a child's exposure.
    • The condition of paint within the home is an important factor in exposure risk, and American Community Survey data does not contain information on housing condition.
    • Older properties that have undergone remediation (e.g., lead hazard removal, enclosure, or encapsulation) may pose less exposure risk.
    • Housing age varies within counties. The percentage of older homes in the county does not determine whether individual children reside in older homes.
  • Vital statistics data from the IDPH Vital Records maintains high quality information on all Iowa births, but errors may occur when using vital statistics data or total births as denominators for the birth cohort lead testing measure. A child's address on a birth certificate, for example, may be different from her/his address at the time of the lead test. Additionally, the number of children born in a specific geographic area does not include children who have moved in or out of that area since birth, so using total births as a denominator may lead to an inaccurate estimation of the number of children tested who are born in a specific year.

Back to top

Where can I find more technical information about the data?

More detailed documentation of the lead poisoning data can be found in the following documents:

Indicator Profiles

Blood Lead Level Testing by Test Year pdf
Blood Lead Level Testing by Birth Cohort pdf
Age of Housing pdf
Child Poverty pdf

Descriptive Metadata

Annual Testing Children Under 6 pdf
Annual Testing Persons 6 and Older pdf
Under 3 Birth Cohort pdf
Under 6 Birth Cohort pdf

Contact Us to learn more about lead poisoning data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

Back to top