These results indicate that place of residence during the Hunger Winter is a reasonably adequate proxy of exposure, although unavoidable misclassification may have caused attenuation of the association.
As carbaryl concentrations in the field are difficult to quantify, we used land use intensity as a proxy of exposure.
In some instances, the exposure simply does not vary spatially in a way that makes location alone a useful proxy of exposure.
The availability of individual data made it possible to overcome the possibly biased approaches using spatial distance from putative environmental sources as a proxy of exposure [ 13].
We also conducted sensitivity analyses using 1-year mean of NO2 at the residential address at enrollment (1993 1997, corresponding to the time period for the self-reported physical activity data) as an alternative proxy of exposure to air pollution.
The distribution pattern and statistical association of the eight PAHs are consistent overall with those for ∑8c-PAH, demonstrating that ∑8c-PAH is an appropriate proxy of exposure to the eight individual carcinogenic PAHs.
Area measurement of air pollutants is often used as a proxy of exposure in epidemiological studies and for the purpose of this paper the two terms will be used interchangeably.
First, when using residential proximity to a monitoring site as a proxy of exposure, the mother's postcode at the time of exposure is unknown; it was recorded only at the date of the ultrasound scan.
Body-worn dosimeters are likely to underestimate daytime exposure due to the influence of the body's own electric activity and night-time measurements are not a valid proxy of exposure [ 23].
Among the 537 participants at the first (baseline) study visit, the average age was 71 years, BMI was 25 kg/m, and creatinine-adjusted urine cotinine as a proxy of exposure to either passive or active smoking was 255 mg/g (Table 1).
As the primary traffic related air pollutants are highest at the roadside and decline exponentially[ 12], we have chosen to use distance between home residence and the nearest major road as an objective proxy of exposure to traffic pollution, and to look particularly at dose-response relations across the first 150 m from the roadside where most of the decline occurs.
