Air samples versus biomarkers for epidemiology.

Area of Science:

• Environmental Epidemiology
• Biomonitoring
• Exposure Science

Background:

• Theoretical considerations suggest biomarkers may offer superior surrogate measures for chemical exposures compared to traditional air sampling in epidemiological research.
• Measurement error is a significant concern for both air samples and biomarkers when used as surrogates for true exposures due to inherent variability.

Purpose of the Study:

• To compare the effectiveness of biomarkers versus air samples as surrogates for chemical exposures in epidemiological studies.
• To quantify the bias associated with different exposure measures by analyzing within- and between-person variance ratios.

Main Methods:

• Classified biomarkers based on their position in the exposure-disease continuum (e.g., parent compound, metabolite, adduct).
• Constructed a database of 12,077 repeated air and biological measurements from 127 datasets.
• Estimated within- and between-person variance components and ratios for air and biomarker measurements.

Main Results:

• Biomarker variance ratios decreased with longer residence times (short-term > intermediate-term > long-term).
• Biomarkers consistently showed smaller variance ratios than air measurements, especially in environmental settings.
• This suggests biomarkers provide less biased exposure surrogates than air measurements.

Conclusions:

• Biomarkers generally offer less biased estimates of exposure compared to air measurements in epidemiological studies.
• Epidemiologists should consider variance ratios, practicality, and cost when selecting exposure surrogate measures.