Limiting the impact of light pollution on human health, environment and stellar visibility

Abstract

Light pollution is one of the most rapidly increasing types of environmental degradation. Its levels have been growing exponentially over the natural nocturnal lighting levels provided by starlight and moonlight. To limit this pollution several effective practices have been defined: the use of shielding on lighting fixture to prevent direct upward light, particularly at low angles above the horizon; no over lighting, i.e. avoid using higher lighting levels than strictly needed for the task, constraining illumination to the area where it is needed and the time it will be used. Nevertheless, even after the best control of the light distribution is reached and when the proper quantity of light is used, some upward light emission remains, due to reflections from the lit surfaces and atmospheric scatter. The environmental impact of this "residual light pollution", cannot be neglected and should be limited too. Here we propose a new way to limit the effects of this residual light pollution on wildlife, human health and stellar visibility. We performed analysis of the spectra of common types of lamps for external use, including the new LEDs. We evaluated their emissions relative to the spectral response functions of human eye photoreceptors, in the photopic, scotopic and the 'meltopic' melatonin suppressing bands. We found that the amount of pollution is strongly dependent on the spectral characteristics of the lamps, with the more environmentally friendly lamps being low pressure sodium, followed by high pressure sodium. Most polluting are the lamps with a strong blue emission, like Metal Halide and white LEDs. Migration from the now widely used sodium lamps to white lamps (MH and LEDs) would produce an increase of pollution in the scotopic and melatonin suppression bands of more than five times the present levels, supposing the same photopic installed flux. This increase will exacerbate known and possible unknown effects of light pollution on human health, environment and on visual perception of the Universe by humans. We present quantitative criteria to evaluate the lamps based on their spectral emissions and we suggest regulatory limits for future lighting.

Seasonal induction of GABAergic excitation in the central mammalian clock

“…Furthermore, considering that GABA is a target for therapeutic treatments of sleep disorders and the role of the SCN in sleep regulating processes, the seasonal influence on GABAergic function may affect the therapeutic manipulation of this neurotransmitter system differently in summer compared with winter. Together, these findings imply that some crucial neuronal networks within the CNS are sensitive to changes in day length, or even to prolonged artificial light exposure common in modern society (28,29).…”

The effects of light pollution on biological rhythms of birds: an integrated, mechanistic perspective

“…In developed countries, very few places can be considered free of light pollution (Cinzano et al 2000 ). If the consequences for activities such as stargazing are evident (Falchi et al 2011 ), the same cannot be stated for wild organisms and the ecological systems they are part of. However, the last decade has seen a boost of interest into the ecological consequences of light pollution Longcore 2006 ; Gaston et al 2013 ), which the symposium "Light in the darkness: how does artificial night lighting influence bird behavior and ecology?"…”

Artificial light-at-night – a novel lifestyle risk factor for metabolic disorder and cancer morbidity

“…MLT suppression by ALAN has a dose-dependent response to both irradiance level and duration of the exposure [223]. Furthermore, the phase advance and suppression in MLT rhythms are intimately wavelength-dependent with more manifested effect at short wavelengths compared with long wavelengths [44,45,224]. Finally, the ALAN-induced MLT suppression is not age-related [225].…”

“…The melanopsin-containing ipRGCs, which regulate the pineal MLT synthesis via the SCN, are extremely sensitive to short wavelength light exposure even at low irradiance [42] and for a short period [43] as they can suppress the synthesis of the pineal hormone MLT. The spectral sensitivity of MLT synthesis suppression demonstrates wavelength-dependent sensitivity with robust effects in response to short wavelength (450-500 nm) exposure [44,45]. Accordingly, a comprehensive study on the effect of various artificial lights on MLT suppression revealed that 4000 K and 5000 K LED lights were the most effective in the suppression of the hormone compared with counterpart technologies, such as incandescent, halogen, and florescent lightening systems [46].…”