Light, lighting and human health

Abstract

Light can impact human health via the visual and non-visual systems originating in the retina of the eye or as optical radiation falling on eye or skin. This paper provides a summary of what is known about these impacts. Topics covered include aspects of lighting likely to cause eyestrain and headaches; increase the risk of falls; induce circadian disruption; enhance sleep; mitigate Alzheimer’s disease and depression; produce tissue damage; alleviate diseases through phototherapy and inactivate viruses through germicidal irradiation. It is concluded that human health is undoubtedly influenced by lighting, but there are four conditions that should be attached to such a simple assertion. First, the impact of lighting on human health can be either positive or negative. Second, human health is affected by many factors other than lighting. Third, the severity of the effects of light exposure can vary widely from the short-lived and trivial to the long-term and fatal. Fourth, the same lighting conditions can have very different health impacts for different individuals depending on their age and medical status. Taken together, these conditions imply that care is required when judging the veracity and relevance of broad assertions about the benefits of lighting for human health.