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In tobacco studies, biomarkers to assess exposure or of potential harm are both of interest. Biomarkers of exposure are tobacco smote constituents or their metabolites in a biological fluid or , tissue, hair, nails, or exhaled breath. They are not measurements of how these constituents interact with the body process/functions. 

The FDA has established a list of harmful and potentially harmful constituents ( HPHCs ) in tobacco products and tobacco smoke (see https://www.fda.gov/tobacco-products/). Additionally, a there is a  list of 20 HPHCs, selected from the full list of HPHCs, for which testing methods are well established and widely available. These The HPHC list focuses on chemicals that are linked to the five 5 most serious health effects of tobacco use (i.e., cancer, cardiovascular disease, respiratory effects, reproductive problems, and addiction.) 

The use of tobacco products results result in the uptake of nicotine and a wide range of other chemicals. Biomarkers of exposure to tobacco and nicotine delivery products are limited to the chemicals taken up during product use or during exposure to product emissions. Total nicotine equivalents (TNE) is a biomarker of nicotine consumption, defined as the molar sum of the urinary concentrations of nicotine and all of its known metabolites . Typically this includes total NIC(e.g., nicotine, total COTcotinine, total 3HC3-hydroxycotinine, and nicotine N-oxide, NNO.  ), is a biomarker of nicotine consumption. Cotinine is a  a metabolite of nicotine and is  is a widely used biomarker of nicotine exposure. Nicotine replacement therapy and tobacco use can be distinguished by the detection of a tobacco-specific alkaloid , such as anabasine. Cotinine has 6 notable metabolites including: 3′(i.e., 3-hydroxycotinine, cotinine glucuronide, 5′5-hydroxycotinine, cotinine N-oxide, cotinine methonium ion, and norcotinine).

Biomarkers of tobacco exposure are typically measured in blood (serum or plasma) and urine. Urine testing are usually recommended to detect chronic use because analytes are detectable for a longer period of time in urine than in serum or plasma. These biomarkers may be used to evaluate evaluated the pharmacokinetic pharmacokinetics of tobacco products. After the specific tobacco product . Typicalis used, when these biomarkers are measured serially after the specific tobacco product is used to determine well-defined pharmacokinetic parameters ( e.g., AUC, TMX, T 1/2 )  ; the concentration level at the pre-specified levels at prespecified timepoints would be represented in the PC/PK SDTM domains ( Section 3.3.3.2, Pharmacokinetics Concentration and Parameters (PC, PP)). Otherwise, otherwise these biomarkers would be represented in the Laboratory Testing Results (LB) domain.