Smoking epidemiological studies

The number of clear human epidemiologic studies is small. A total of approximately 50 compounds (c.g., benzene, vinyl chloride) and complex e.xposures (e.g., aluminum production, tobacco smoke) have sufficient data available to permit their classification as human carcinogens. The most potent human carcinogens known, the aflatoxins. are of natural origin. Their presence in food products through infestation by toxin-producing fungi constitute a serious problem in several tropical and subtropical countries. 

According to EPA (IRIS 1999), the available human epidemiological studies lack quantitative exposure data for lead and for possible confounding exposures (e.g., arsenic, smoking). Cancer excesses in the lung and stomach of lead-exposed workers that are reported are relatively small, dose-response relationships are not demonstrated neither is there consistency in the site of cancers reported. EPA (IRIS 1999) concluded that the human data are inadequate to refute or demonstrate the potential carcinogenicity of lead exposure. 

Increased age and smoking are associated with an increased oxidative stress and depletion of low-molecular weight antioxidants in many tissues including the retina (Beatty et al., 2000). Epidemiological studies indicate that on average, smokers develop late stage AMD 10 years earlier than nonsmokers (Kelly et al., 2004 Klein et al., 1998 Mitchell et al., 2002 Thornton et al., 2005 Tomany et al., 2004). 

A number of epidemiological studies have been conducted to evaluate the association between lung cancer and occupational exposure to acrylonitrile (Collins et al. 1989 Delzell and Monson 1982 Kiesselbach et al. 1979 O Berg 1980 O Berg et al. 1985). Flowever, many of the studies suffer from deficiencies such as an insufficient quantification of exposure, short follow-up, small and relatively youthful cohorts or lack of consideration of the effects of smoking, and the results of the studies are often inconsistent. 

Of course individual people can, for causes under their personal control, also benefit from the results of epidemiology studies even though epidemiology results apply to populations, individuals at least have an increased chance of benefiting by avoiding the substances or factors identified as causes of disease, especially when, as in the case of smoking, the population risk from the causative agent is unusually... 

Although a number of epidemiological studies have reported an increased risk of lung cancer among occupationally exposed beryllium workers, deficiencies in the studies limit any unequivocal conclusion. Specific criticisms concern the lack of consideration of latent effects, of smoking history, and of exposure to other potential carcinogens and the underestimation of expected lung cancer deaths in comparison populations. "... 

There is some USEPA precedent for use of statistical meta-analysis in a regulatory context, including the recent meta-analysis of organophosphate-related acetylcholinesterase inhibition data and meta-analysis of epidemiological studies on effects of 2nd hand tobacco smoke exposure. Warren-Hicks and Moore (1998) provide some discussion of the potential applicability of meta-analysis to ecological risk assessments. 

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