Measurement Challenges at Low Blood Lead Levels

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.