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Measurement Challenges at Low Blood Lead Levels
Kathleen L Caldwell1, Po-Yung Cheng2, Jeffery M Jarrett2
1Division of Laboratory Sciences, National Center for Environmental Health, Centers for Disease Control and Prevention, Atlanta, Georgia kcaldwell@cdc.gov.
Insights
The Centers for Disease Control and Prevention (CDC) updated the reference value for childhood blood lead levels (BLLs) to 3.48 µg/dL. This highlights challenges in accurately measuring low BLLs and improving laboratory performance.
Area of Science:
- Environmental Health
- Public Health
- Toxicology
Background:
- The CDC uses a population-based reference value to identify children with lead hazards.
- The current reference value is the 97.5th percentile of blood lead levels (BLLs) from NHANES 2007-2010 data.
- Accurate measurement of low BLLs is crucial for public health interventions.
Purpose of the Study:
- To update the 97.5th percentile BLL using newer NHANES data (2011-2014).
- To examine demographic characteristics of children with elevated BLLs (≥90th percentile).
- To identify and address analytical challenges in measuring low BLLs.
Main Methods:
- Calculated updated percentiles of BLLs using NHANES 2011-2014 data.
- Examined demographic data for children with BLLs at or above the 90th percentile.
- Reviewed proficiency testing data from US clinical laboratories for BLLs <11 µg/dL.
Main Results:
- The updated 97.5th percentile BLL is 3.48 µg/dL.
- Significant challenges exist in laboratory quantification of BLLs ≤5 µg/dL.
- 40% of laboratories could not quantify BLLs at 1.48 µg/dL, compared to 5.5% at 4.60 µg/dL.
Conclusions:
- The updated reference value of 3.48 µg/dL underscores the need for improved analytical methods for low BLLs.
- Enhancements at the CDC's Environmental Health Laboratory aim to improve accuracy and reduce contamination.
- Addressing laboratory performance is critical for accurate identification and management of childhood lead exposure.
Abstract:
In 2012, the Centers for Disease Control and Prevention (CDC) adopted its Advisory Committee on Childhood Lead Poisoning Prevention recommendation to use a population-based reference value to identify children and environments associated with lead hazards. The current reference value of 5 microg/dL is calculated as the 97.5th percentile of the distribution of blood lead levels (BLLs) in children 1 to 5 years old from 2007 to 2010 NHANES data. We calculated and updated selected percentiles, including the 97.5th percentile, by using NHANES 2011 to 2014 blood lead data and examined demographic characteristics of children whose blood lead was ≥90th percentile value. The 97.5th percentile BLL of 3.48 µg/dL highlighted analytical laboratory and clinical interpretation challenges of blood lead measurements ≤5 microg/dL. Review of 5 years of results for target blood lead values <11 µg/dL for US clinical laboratories participating in the CDC's voluntary Lead and Multi-Element Proficiency quality assurance program showed 40% unable to quantify and reported a nondetectable result at a target blood lead value of 1.48 µg/dL, compared with 5.5% at a target BLL of 4.60 µg/dL. We describe actions taken at the CDC's Environmental Health Laboratory in the National Center for Environmental Health, which measures blood lead for NHANES, to improve analytical accuracy and precision and to reduce external lead contamination during blood collection and analysis.
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