Light Exposure during Days with Night, Outdoor, and Indoor Work
Level 3 - non-randomized controlled study
Prospective observational exposure study comparing light dosimetry across occupational cohorts
OpenAlex W2922433488 · doi:10.1093/annweh/wxy110
What was done
Continuous personal light intensity was monitored for 7 days across seasons among 509 Danish workers (170 indoor, 151 outdoor, and 188 night workers) located at 55–56°N. Dosimeters recorded white light intensity, duration of exposure above 80, 1000, and 2500 lux, and the spectral composition (proportions of red, green, and blue light) during work days and days off across time of day and season.
What was found
During daytime work hours, indoor workers' average exposure intermittently exceeded 1000 lux in summer and never exceeded 1000 lux in winter. Most outdoor workers exceeded 2500 lux in summer and 1000 lux in winter during daytime shifts. Night workers were exposed to >80 lux for an average of 10 to 50 minutes during night shifts. On days off, indoor and night workers experienced higher light exposure than on work days, resulting in few differences between worker groups. Spectral composition of light was similar across indoor, outdoor, and night workers during work and off days.
Why it matters
This study provides objective dosimetric quantification showing that typical indoor work environments provide very low light intensity, especially in winter at northern latitudes, whereas night workers experience light levels capable of triggering biological circadian disruption.
Limits
Conducted at high latitude in Denmark (55–56°N), limiting generalizability to sunnier or lower-latitude locations. Health and biological outcomes—such as direct melatonin suppression, circadian phase shifts, or mood alterations—were not measured directly, only inferred from exposure thresholds. Specific job roles, sensor wear compliance, and exact variance metrics are not detailed in the abstract.
Cited by
- supports Ambient outdoor light on a cloudy day delivers around 5,000 lux of light intensity.