investment seems justified. Decreasing the sample sizes in national population surveys or limiting population coverage may cause compromises in data quality or generalizability. A related issue is that it might take very large population surveys to adequately cover important demographic subgroups of interest, such as pregnant women or certain minority groups. Thus, it may be more efficient to have separate surveys or surveillance surveys of special populations than only one large population survey. A comprehensive surveillance system, as described in this chapter, could also be critical for other disease control activities that are not tobacco-related, and conceivably the cost of the system could be shared.
Another important limitation is that many aspects of population surveillance depend largely on self-report, which can be subject to error. In some instances, tobacco product usage can be validated by external means, but not in all circumstances. There are also limitations to predicting behaviors based on self-reported personal knowledge and attitudes, although both are important. Here, too, there are mechanisms to improve the validity of these reports.
There may not be suitable or logistically feasible biomarkers of exposures for the range of important tobacco products and toxicants to which users are exposed. Some of the biomarkers of exposure used in the past, such as cotinine, may still have utility for assessing conventional tobacco product exposure, but as new PREPs come to the marketplace, these markers may no longer be fully suitable because they won’t necessarily serve as adequate surrogate markers for the range of major tobacco constituents.
Some elements of a comprehensive surveillance system, such as mandating tobacco manufacturers to report product characteristics, ingredients, additives, and brand-specific sales and distribution data might require a legislative or regulatory approach to enforce. Without this information, a comprehensive surveillance program would be much weaker.
Finally, it should be noted that it is not the burden of surveillance systems per se to relate PREPs or other tobacco product exposure to specific health outcomes or altered levels of those outcomes. That is usually the function of targeted epidemiological studies such as cohort studies of persons using PREPs to monitor for long-term health effects, with suitable contrast groups. Well-designed case-control studies may also be appropriate vehicles for exploring certain tobacco-disease associations, although the retrospective recall of the past product usage may not always be credible. As always, epidemiological studies should be accompanied by the best basic science and clinical research to guide the study design, apply the most modern markers of exposure and disease, and optimally interpret the findings.