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The birth cohort children under 3 data provides information about blood lead testing and Blood Lead Levels (BLLs) among children born in the same year, known as a birth cohort. This indicator evaluates all BLL test results prior to a child’s third birthday. These data can be used to identify changes in blood lead levels over time and to monitor progress toward reducing and preventing exposure to lead in children. This indicator also includes age of housing and child poverty rates from the American Communities Survey that can help assess testing within areas of high risk.
Elevated BLLs in young children have been associated with adverse health effects ranging from learning impairment and behavioral problems to death. Because children may have elevated BLLs and not have any specific symptoms, it is recommended that all young children be tested prior to the age of three. Evaluating BLLs in children under the age of three is important because the first three years of life is the time when the brain grows the fastest and when the critical connections in the brain and nervous system are formed.
These measures are presented together with data about the number of homes built before 1950 and the poverty level in a specific area. Pre-1950s homes and living in poverty have been identified as risk factors for elevated blood lead levels in children. Having all of this information together helps assess testing within areas of high risk.
The children tested measures in the under 3 birth cohort evaluate all blood lead level (BLL) tests of children before their third birthday. Children are grouped based on the year they were born (the birth cohort year). Evaluating blood lead levels in children under the age of three is important because the first three years of life is the time when the brain grows the fastest and when the critical connections in the brain and nervous system are formed.
Measure Description
The Children Tested is the number of children born in the birth cohort year and tested for blood lead level (BLL) before age three.
The Children with Confirmed Elevated BLL is the number of children born in the birth cohort year and tested for blood lead level (BLL) before age three and had a confirmed result greater than or equal to 10 mcg/dL.
The Percent of Children with Confirmed Elevated BLL is the percent of children tested that had Confirmed Elevated BLL result.
Iowa requires all children to be tested at least once before the age of six. The recommendation is to start testing prior to age three. The under 3 birth cohort testing data can be helpful for healthcare providers and local public health agencies for program assessment and improvement; however, the Birth Cohort Children Under 6 is a better indicator of compliance with the testing requirement.
The number of children born from Vital Statistics data does not include children who have moved in or out of the area since birth. Therefore, as a denominator, vital statistics data may under or overestimate the number of 3 year old children in the area. It is possible that there were more children tested in a County during the time period than were born in that County causing the Percent of Birth Cohort Tested to be greater than 100%.
Measure Description
The Children Tested is the number of children born in the Birth Cohort Year with at least one BLL test before their third birthday.
The Percent of Birth Cohort Tested is the percent Children Tested among the number of children born in the Birth Cohort Year.
The Percent Under 5 Child Poverty is the percent children under five living in poverty as reported in the American Community Survey.
The Percent Pre 1950 Housing is the percent of housing units built before 1950 as reported in the American Community Survey.
Age of Housing and Child Poverty are two of the major risk factors that have been associated to exposure to lead. These measures can be used to help assess high risk areas and direct resources.
Measure Description
The Children Tested is the number of children born in the Birth Cohort Year with at least one BLL test before their third birthday.
The Percent of Birth Cohort Tested is the percent Children Tested among the number of children born in the Birth Cohort Year.
The Percent Under 5 Child Poverty is the percent children under five living in poverty as reported in the American Community Survey.
The Percent Pre 1950 Housing is the percent of housing units built before 1950 as reported in the American Community Survey.
The number and percent of children tested for blood lead prior to 3 years of age in Iowa, based on their 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.
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.
To inform the public about testing coverage for blood lead levels in children and elevated blood lead levels.
For program planning and evaluation by state and local partners
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.
Data on blood lead testing and elevated blood lead levels are provided by Iowa HHS 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.
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.
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.
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. Iowa HHS Childhood Blood Lead Screening Guidelines direct physicians to order blood lead tests for certain populations at higher risk for lead exposure.
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 Iowa HHS 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.
More detailed documentation of the lead poisoning data can be found in the following documents:
