Smoking is a known risk factor for renal cell carcinoma [ 25] and our results are consistent with smoking prevalence by ethnic group [ 26].
This was consistent for smoking cessation and breast feeding.
Positive exposure to nicotine, which is consistent with smoking, will be defined by cotinine ≥10 ng/mL.
The evidence seems more consistent for smoking where data indicating a positive relationship with smokeless tobacco use are seen in published studies in the USA [ 59, 71, 72] and in Sweden [ 73] and also in unpublished data provided by Statistics, Sweden (I Sjöberg, personal communication).
Our data are consistent with smoking-induced liver CYP1A2 activity altering heme metabolism and increasing the biotransformation of mono- ortho PCB congeners.
Recent studies demonstrated that having a parent who smokes or smoked is another strong and consistent predictor of smoking initiation [ 20- 26], while parental expectations not to smoke are protective [ 27].
The evidence of adverse effect of occupational dust exposure on COPD is not consistent compared with smoking [ 26- 29], and we have adjusted the main risk factor like smoking and passive smoking.
The mean (± SD) age of study participants was 29.5 ± 4.3 years, 12.8% had plasma cotinine levels consistent with active smoking (Shaw et al. 2009), and 11.7% reported current smoking during pregnancy (Table 1).
Among our MoBa study participants, 8 of the 136 women (5.9%) with cotinine values consistent with active smoking (≥ 56.8 nmol/L) reported that they did not smoke during pregnancy.
Irrespective of full understanding of the pathophysiological mechanisms, strong and consistent associations with smoking of a variety of CpG sites suggest their potential use as main correlates for smoking exposure.
