4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL) is a tobacco-specific nitosamine metabolite that can help to distinguish active from passive tobacco exposure.
Half-life of NNAL in the urine: 10 to 16 days
Half-life of cotinine in the urine: 16 to 19 hours
Units of measurement for NNAL: pg/mL (ng/L)
Units of measurement for cotinine: ng/mL (µg/L)
Urine Cotinine
Interpretation
< 10 ng/mL
nonsmoker or passive exposure or short-term abstinence
10 to 100
probable passive exposure
100 to 500
probable active smoker
> 500
active smoker
from Figure 1 page 205
Urine NNAL
Interpretation
< 3 pg.mL
nonsmoker or passive exposure
3 to 10
probable passive exposure
10 to 47.3
uncertain (mix of active and passive smokers)
47.4 to 100
probable active smoker
> 100 pg/mL
active smoker
from Figure 2 page 205
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