In these high-exposure cases, occupational workers are exposed to, on average, approximately 0.74 ppm (WHO 2001).
High-exposure cases are chosen in LD studies to mitigate the problem of ongoing background exposure (Grandjean et al. 2008).
Coggin et al. (2003) also assessed a subcohort of 4000 men with high exposure (>2ppm); no cases of NPC were observed.
More case mothers had low exposure compared with control mothers and more control mothers had moderate or high exposure compared with case mothers (P=0.052) (Table 2).
All smoking variables showed higher exposure among cases than among cohort members, including proportion of smokers at enrollment, smoking intensity, duration of smoking, and exposure to ETS.
Second, the periods during which exposures are ascertained for FoodNet case-control studies tend to be long (5 7 days), so the likelihood of detecting a difference in exposure between cases and controls is limited by high exposure frequencies among both cases and controls.
The aORs for PCE and vinyl chloride were based on two cases with high exposure and the aOR for DCE was based on three cases with high exposure.
For example, in the logistic regression analyses, the results for PCE and vinyl chloride were based on two cases with high exposure and the result for DCE was based on three cases with high exposure.
For average exposure to PCE, there was an exposure-response relationship for the unadjusted OR analysis; these results were based on two cases with low exposure and two cases with high exposure.
However, this influence is only detectable if there are large differences in the consumption of vegetables and fruit between the groups and could appear only in case of high exposure to carcinogens, like, for example, in smokers.
However, this study was limited by small numbers of cases in high exposure categories.
