MEASUREMENT ERROR IN AIR-POLLUTION EXPOSURE ASSESSMENT

The exposure of an individual to an air pollutant can be assessed indi rectly, with a ''microenvironmental'' approach, or directly with a per sonal sampler. Both methods of assessment are subject to measurement e rror, which can cause considerable bias in estimates of health effects . If the exposure estimates are unbiased and the measurement error is nondifferential, the bias in a linear model can be corrected when the variance of the measurement error is known. Unless the measurement err or is quite large, estimates of health effects based on individual exp osures appear to be more accurate than those based on ambient levels.