Nicotine Absorption During Tobacco Harvesting: A Scoping Review of Urinary Cotinine Levels Among Tobacco Farm Workers

Tobacco farm workers have a high prevalence of acute nicotine poisoning, known as green tobacco sickness, caused by dermal exposure during leaf harvesting. Although urinary cotinine is the most reliable biomarker of nicotine exposure, methodological inconsistencies across studies hinder the identification of absorption patterns and limit comparability. This scoping review aimed to summarize methods used to assess urinary cotinine, identify individual and occupational factors influencing its measurement, and examine temporal patterns of urinary cotinine levels.

The review followed JBI guidance and was reported in accordance with PRISMA-ScR. It was structured using the PCC framework: Population - tobacco farm workers aged ≥ 13 years; Concept - dermal nicotine exposure indexed by urinary cotinine; Context - harvesting. Searches were conducted in MEDLINE (PubMed) and LILACS without date limits, including studies in Portuguese, English, and Spanish. Two reviewers independently screened studies and extracted data.

Eleven cross-sectional, three case-control, and one intervention study met the inclusion criteria. Marked heterogeneity was found in laboratory methods (e.g. spectrophotometry, immunoassays, HPLC/GC-MS), measurement units, creatinine adjustment (rarely applied), sampling schedules, and reporting of humidity and personal protective equipment (PPE) use. In studies with repeated sampling, urinary cotinine generally peaked the day after harvesting began, clarifying the best time to carry out the urine collection. Associations of cotinine with sex, moisture, and PPE use were inconsistent. Compared with occupationally unexposed groups - both smokers and non-smokers - tobacco workers typically had higher urinary cotinine. Small, often non-representative samples and limited adjustment for confounding reduced comparability and precluded quantitative synthesis.

Tobacco workers may experience nicotine exposures comparable to or exceeding those of heavy smokers. This underscores the need for research into the health effects of intense, cumulative (over successive harvesting days) and chronic exposure in this population. Future studies should adopt standardized protocols specifying urine collection on the day after exposure, creatinine adjustment, systematic assessment of humidity, PPE use, smoking status, and other determinants, alongside robust sampling strategies and adequate sample sizes. Such measures would strengthen occupational exposure assessment and support surveillance and prevention of nicotine-related illness among tobacco farm workers.