Engineering topics

Hanifin, John P.

Publications and source records attributed to Hanifin, John P..

3 records

DOE OSTI2022

Impact of Solid State Roadway Lighting on Melatonin in Humans

Introduction: In 2009, the World Health Organization identified vehicle crashes, both injury-related and fatal, as a public health hazard. Roadway lighting has long been used to reduce crashes and improve the safety of all road users. Ocular light exposure at night can suppress melatonin levels in humans. At sufficient light levels, all visible light wavelengths can elicit this response, but melatonin suppression is maximally sensitive to visible short wavelength light. With the conversion of roadway lighting to solid state sources that have a greater short wavelength spectrum than traditional sources, there is a potential negative health impact through suppressed melatonin levels to roadway users and those living close to the roadway. This paper presents data on the impact of outdoor roadway lighting on salivary melatonin in three cohorts of participants: drivers, pedestrians, and those experiencing light trespass in their homes. Methods: In an outdoor naturalistic roadway environment, healthy participants (N = 29) each being assigned to a cohort of either pedestrian, driver, or light trespass experiment, were exposed to five different solid state light sources with differing spectral emissions and one no lighting condition. Salivary melatonin measurements were made under an average roadway luminance of 1.0 cd/m2 (IES RP-18 Roadway Lighting Requirements for expressway roads) with a corneal melanopic Equivalent Daylight Illuminances (EDI) ranging from 0.22 to 0.86 lux. Results: The results indicate that compared to the no roadway lighting condition, the roadway light source spectral content did not significantly impact salivary melatonin levels in the participants in any of the cohorts. Conclusions: These data show that recommended levels of street lighting for expressway roads do not elicit an acute suppression of salivary melatonin and suggest that the health benefit of roadway lighting for traffic safety is not compromised by an acute effect on salivary melatonin.

60 APPLIED LIFE SCIENCES↗

NASA NTRS2005

Photons, clocks, and consciousness

Light profoundly impacts human consciousness through the stimulation of the visual system and powerfully regulates the human circadian system, which, in turn, has a broad regulatory impact on virtually all tissues in the body. For more than 25 years, the techniques of action spectroscopy have yielded insights into the wavelength sensitivity of circadian input in humans and other mammalian species. The seminal discovery of melanopsin, the photopigment in intrinsically photosensitive retinal ganglion cells, has provided a significant turning point for understanding human circadian phototransduction. Action spectra in humans show that the peak wavelength sensitivity for this newly discovered sensory system is within the blue portion of the spectrum. This is fundamentally different from the three-cone photopic visual system, as well as the individual rod and cone photoreceptor peaks. Studies on rodents, nonhuman primates, and humans indicate that despite having a different wavelength fingerprint, these classic visual photoreceptors still provide an element of input to the circadian system. These findings open the door to innovations in light therapy for circadian and affective disorders, as well as possible architectural light applications.

Review↗

NASA NTRS2003

Inferior retinal light exposure is more effective than superior retinal exposure in suppressing melatonin in humans

Illumination of different areas of the human retina elicits differences in acute light-induced suppression of melatonin. The aim of this study was to compare changes in plasma melatonin levels when light exposures of equal illuminance and equal photon dose were administered to superior, inferior, and full retinal fields. Nine healthy subjects participated in the study. Plexiglass eye shields were modified to permit selective exposure of the superior and inferior halves of the retinas of each subject. The Humphrey Visual Field Analyzer was used both to confirm intact full visual fields and to quantify exposure of upper and lower visual fields. On study nights, eyes were dilated, and subjects were exposed to patternless white light for 90 min between 0200 and 0330 under five conditions: (1) full retinal exposure at 200 lux, (2) full retinal exposure at 100 lux, (3) inferior retinal exposure at 200 lux, (4) superior retinal exposure at 200 lux, and (5) a dark-exposed control. Plasma melatonin levels were determined by radioimmunoassay. ANOVA demonstrated a significant effect of exposure condition (F = 5.91, p < 0.005). Post hoc Fisher PLSD tests showed significant (p < 0.05) melatonin suppression of both full retinal exposures as well as the inferior retinal exposure; however, superior retinal exposure was significantly less effective in suppressing melatonin. Furthermore, suppression with superior retinal exposure was not significantly different from that of the dark control condition. The results indicate that the inferior retina contributes more to the light-induced suppression of melatonin than the superior retina at the photon dosages tested in this study. Findings suggest a greater sensitivity or denser distribution of photoreceptors in the inferior retina are involved in light detection for the retinohypothalamic tract of humans.

NASA Discipline Space Human Factors↗