Multi-parameter characterization of indoor air quality in a medical marijuana cultivation facility in Oklahoma: a pilot study of occupational exposure determinants.

Li H.; Yang Y.; Yang A.; Cheng W. · Annals of work exposures and health · 2026

**Background & Methods** This pilot study conducted continuous multi-parameter air quality monitoring in a 186 m² indoor medical cannabis cultivation facility in Oklahoma housing ~900 plants over 23 days (July 10–August 1, 2023). Seven instruments measuring CO₂, particulate matter (PM), volatile organic compounds (VOCs), and thermal-humidity conditions were deployed across three spatial zones at breathing zone height (1.5 m), generating approximately 113,000 quality-controlled records for analysis. **Key Findings** • CO₂ concentrations exhibited photoperiod-linked diurnal patterns driven by the plant light/dark cycle, with mean levels ranging from 979–1,086 ppm and maximum concentrations exceeding 2,200 ppm; elevated nighttime CO₂ reflected plant metabolism and intermittent CO₂ enrichment rather than worker respiration. • Median PM₂.₅ concentrations were generally low (1.4–3.1 µg/m³), but episodic spikes reached 5,000–35,000 µg/m³, with the largest daytime excursion coinciding with in-flower canopy maintenance activities (trimming, defoliation). • Mean total volatile organic compound (tVOC) concentrations reached 3.61 mg/m³, with ethanol proxies exceeding 8,000 ppb at the 95th percentile; temperature and relative humidity frequently reached levels potentially increasing heat stress risk and sensor performance artifacts. **Dosage & Administration** Not reported. **Safety & Adverse Effects** Not reported. However, the study identifies potential occupational hazards including elevated CO₂ concentrations, episodic particulate matter spikes, VOC exposure, and extreme thermal-humidity conditions that may pose respiratory risks and heat stress to cannabis workers. **Evidence Quality** This pilot study has significant limitations: single-facility design limits generalizability; short 23-day monitoring period may not capture seasonal variability; lack of worker health outcome data; no comparison to occupational exposure limits or established standards; and potential sensor performance artifacts under high-humidity conditions. The study provides descriptive exposure characterization rather than causal inference. However, it represents the first published air quality characterization of Oklahoma cannabis cultivation facilities and addresses a critical knowledge gap in occupational cannabis research. The authors appropriately acknowledge the urgent need for expanded cannabis-specific occupational health research, standardized ventilation guidance, and worker health surveillance programs.

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