What is the most reliable method for determining nicotine exposure in both smokers and nonsmokers?

Measuring blood cotinine levels is considered the most reliable method for determining nicotine exposure in both smokers and nonsmokers. Cotinine is a metabolite of nicotine, which means that when nicotine enters the body, it is metabolized into cotinine. The presence and concentration of cotinine in the bloodstream provide a direct indication of nicotine exposure, reflecting both the amount of tobacco consumed and, in nonsmokers, exposure to secondhand smoke.

This method is particularly effective because it offers a quantitative measure that can be obtained through a blood sample, making it less susceptible to biases that can affect self-reported habits, such as over- or under-reporting of smoking behavior. Additionally, while exhaled breath measurements and urine analyses can also provide information about nicotine exposure, they are generally considered less accurate than blood tests, as they can be influenced by factors such as the timing of measurement and the individual’s metabolism. For instance, cotinine remains in the blood for a longer duration than nicotine itself, thus providing a more stable indicator over time for recent exposure.

In summary, measuring blood cotinine levels presents a reliable and objective way to ascertain nicotine exposure, making it the preferred choice in both clinical and research settings.