Comparison of Carboxyhemoglobin Concentrations in Adult Nonsmokers with Ambient Carbon Monoxide Levels

Abstract

Blood samples from several thousand current nonsmokers were collected by the National Center for Health Statistics between 1976 and 1980 in a national probability survey (NHANES II). The blood samples were analyzed for carboxyhemoglobin (COHb) levels using highly sensitive techniques by two laboratories under rigorous quality control procedures. COHb levels of 1528 persons were compared to the immediately preceding one-hour and eight-hour ambient carbon monoxide (CO) averages in 20 U.S. cities. Spearman rank correlation coefficients between COHb and ambient CO were not significant for a large majority of fixed monitoring stations in the 20 cities. No improvement was shown when the comparisons were limited to central-city residents. A regression of all 1528 COHb values on the “best” ambient stations in each city resulted in an R² value of 0.03, i.e., 3% of the variance in COHb concentrations was explained by the fixed stations.

We conclude that fixed outdoor CO monitors are not, in general, providing useful estimates of carbon monoxide exposures of urban residents. This finding calls into question the assumptions underlying the national policy of attempting to protect public health by setting an outdoor standard for CO.