There was a suggestion of a modest decrease in birth weight with higher exposure based on continuous exposure measures {somewhat stronger for male births [see Supplemental Material, Table 1 (http://dx.doi.org/10.1289/ehp.1104752)]}, but no monotonic gradient across quintiles.
Tissue levels of saturated fat are not always valid measures of dietary saturated fat, and associations based on these exposure measures are difficult to interpret because of shared endogenous and exogenous sources.
Observational data used to determine BMDs and BMDLs are based on exposures that are seldom measured without error.
While our estimates of in-home exposure were based on published exposures measured in homes in urban areas, it is possible that in-home exposures in NYC are higher than other areas due to factors such as population density, housing stock quality, and street traffic volumes.
The method of FA exposure has limitations as the estimates were predicted by means of interviews and mathematical models and were not based on measured exposures.
Several of the studies with positive findings are also based on aggregate measures of exposure, and although misclassification of the exposure is likely a problem in such studies, Feychting says, publishing only those with positive findings would give a false impression of consistency.
Similarly, epidemiologic studies often report results using analyses based on logarithmically transformed exposure measures.
Furthermore, as environmental regulations set acceptable exposure limits based on outdoor measures, we believe that this exposure is most relevant from the public health perspective.
We compared the results based on our primary exposure measure (NO2 since 1971) with those for four alternative exposure measures: NO2 since 1991, NO2 at the baseline address, presence of a major road within 50 m and total traffic load within 200 m of the baseline address (Table 3).
These data have often supplemented or even supplanted estimates of exposure based on environmental measures.
