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—Dr Domino notes that our estimate of dietary nicotine contribution to cotinine (0.02 ng/mL) is below the limit of detection (sensitivity) of our analytical method. We agree that our estimate of dietary nicotine contribution is less than the detection limit of our method and represents a small contribution. Such an estimate can be made because we had cotinine data on thousands of persons in the regression analysis. From our Figure 2, Domino states that the maximum serum cotinine levels peak at approximately 0.1 ng/mL. The maximum is actually much greater than 0.1 ng/mL—the geometric mean we reported (Table 4) was 0.113 to 0.124 ng/mL, depending on age group.Since our study provides, to our knowledge, the only data available in the literature that relates measured levels of cotinine to dietary consumption, we thought it was important to provide an estimate of the contribution of diet to cotinine levels even though
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