Abstract
Indoor light pollution threatens human health. This study examined how built environment characteristics affect nighttime light levels in the bedrooms of urban areas. Indoor illuminances were monitored in the bedrooms of 28 participants in the city of Daejeon, Korea, between 2 a.m. and 4:30 a.m. over five days. Five built environment variables surrounding the bedrooms under study were assessed. Results illustrate that residential floor area on floors of influence (±3 floors from the bedroom under study) increased indoor illuminance, but residential floor area on all floors, including those vertically distant from the bedroom, did not. Tree canopy percentage reduced indoor illuminance, suggesting that tree canopies block artificial light at night emitted at ground level. Non-residential floor area and length of road lanes did not have significant effects, further suggesting that tree canopies protect urban residents on upper floors from light directed upwards from streets and commercial facilities at ground level. These findings indicate that vertical separation of residential areas is an effective measure to mitigate light pollution, especially in high-density urban areas where horizontal separation is not feasible. These findings also imply that policy efforts should focus on reducing light trespass from neighbors at similar heights.
Published Version
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