The research letter “Menthol levels in cigarettes from eight manufacturers” reports concentrations of menthol in whole cigarettes from eight manufacturers in the United States. As our research has progressed, we have re-examined our results and have identified an error in the calculations that were used to determine the reported menthol concentrations. The analytical method used to quantitate menthol concentrations in whole cigarettes was originally developed for only unburned tobacco (eg, tobacco filler). When the method was applied to whole cigarettes, we discovered that we did not account for the mass of the tobacco (400 mg) that was used in the validation of the analytical method. Because the calibration curve originally used to quantitate menthol concentrations has units of μg/g, the cigarette mass was also applied incorrectly. As a result, the calibration curve and subsequent product menthol concentrations quantitated under the original conditions in μg/g should have been adjusted by a factor of 0.4 to provide the correct concentration of menthol found in each cigarette product (μg/cig). Figure 1, has been revised to reflect the correct menthol concentrations from the different manufacturers. Table 1 contains the measured menthol concentration ranges for each manufacturer so that readers can see the measured menthol concentrations used to create figure 1. Because the calculation error applies to all products, relative concentration comparisons made in the manuscript between products remain unchanged.

The manuscript contains discussion on product comparisons that require modification. None of the measured menthol contents exceed 10 mg/cigarette. RJ Reynolds’ Capri Green has the least measured menthol content (1.31 mg/cigarette) among the tested menthol cigarettes. However, this lowest measured menthol is above the menthol perception threshold of 1 mg/g of tobacco [Ref six in original paper; Hopp R. Menthol: its origin, chemistry, physiology and toxicological properties. Rec Adv Tobacco Sci 1993;19:3–46]. Corrected menthol amounts are shown in table 2 below.

The analytical method remains fit for purpose. After investigation, the validation parameters and errors in reported menthol concentrations were found to be solely due to the mathematical issue discussed above. Overall, the conclusions of the manuscript are unaffected by the changes to reported menthol concentrations.