The daylight hours stretch and yawn – extending themselves into the blue edges of the night. I awaken to stars and remind myself that soon they will change – my navigable position on this planet under a glittering sky. This intergenerational knowledge passed into my mind as a child is far older than anyone in my family can remember. My grandfather taught my father and they taught me. Should I ever be lost, wait for nightfall and gain orientation by listening to where the night sky tells you to go. This comfort of belonging and knowing my place in the world is the definition of solace. Cities and light pollution strip me of a knowledge so ingrained in my neurological system I can barely explain with verbal language how I know where to go. I become disoriented.
It took my first trip to the antipodes for me to understand this fully, and not for any reason related to light pollution. Instead, when I stared up into the sky, I failed to orient myself with any landmarks. Gasping for breath in the consuming sea of stars, to gain footing I required the Southern Cross. And even with this point established, it was no Polaris, not in the way I knew or expected. Over my time in New Zealand I gained orientation, at one point finding myself in a forest of glow worms with a full dark sky above. As I traveled elsewhere in the South Pacific, the Southern Cross failed as my anchor.
Having watched and photographed galaxy rises, my back against the earth as it hurdles through space, I ponder the impacts of light pollution on those with celestial navigation as a part of their blood, be it land or sea. Before city lights, for hundreds of thousands of years, humans evolved, watching the stars and orienting ourselves alongside their existences, giving their clusters names. We immortalized warriors, kings, ethical dilemmas, and the foundations of our beliefs in Super Novas, Neutron Stars, White Dwarfs and so many other identified and yet to be identified or understood dots of light filtering through our atmosphere from billions of light years away.
And now we can’t see them. Nor can our children. Nor could many of my peers during their formative years. But what impact is this having on our health?
In December, 2020, the Southern Economic Journal published the first ever study on the link between premature births and light pollution. This showed a 12.9% increased likelihood of preterm birth associated being able to only see 0.25 – 0.33 of stars visible under dark sky conditions. Skyglow, as measured by Walker’s Law (the sky-glow intensity from a light source is approximately proportional to the distance raised to the −2.5 power), has a direct impact of fetal health. Premature birth increases the risk of neonatal mortality. Premature birth of a child is closely associated with postpartum depression in mothers.
But this is not the first time researchers have raised concerns about the link between light pollution and impacts to human health. In 2011, the journal Medical Hypotheses published a review article on light pollution’s disruption of circadian rhythm potentially contributing to the rise in obesity. These impaired metabolic processes relate to circadian gene expression conserved through all mammalian species that regulate at least 10% of our genomes, including those of household pets. This article discusses the comparative obesity problems observed in domesticated animals (including horses!) living alongside humans under light pollution conditions. Going into more detail the health impacts of circadian disruption, the article mentions studies on shift work’s impacts on the release of hormones such as insulin independent of lifestyle choices by individuals. Shift work’s negative impacts on health, while linked to light pollution by exclusion of other causes, has additional epidemiological evidence to back it up. Let’s return to that question of gene expression and focus on the metabolic gene clock. Yes. That’s the actual name.
The International Journal of Environmental Research and Public Health published a review Lighting in the Home and Health this month (January 2021). Focusing on the impacts of types of lighting and its impacts on human health they concluded that though not enough studies exist at this time. Their review found suggests insufficient natural lighting increased risks for infectious diseases, injuries, and self-reported depression. While reviewing artificial lighting, they divided the data into multiple categories: fuel based lighting and electric lighting. While fuel based lighting was associated with adverse health from the toxic effects of the burning fuel (asthma, increased risk of respiratory infection, etc) and potential physical injuries, the lighting provided lower self-reported depression with even minimal usage. However, the toxic effects of the burning fuel varied greatly based on the fuel, whereas the increased infection risk remained constant among electric light users. Artificial lights were found to be associated with increased incidence of farsightedness in some children.
The strongest impacts from artificial lighting came from its use after dark, impacting sleep quality and subsequently health. The most notable health impacts from prolonged exposure to artificial light (regardless of lifestyle) at night included primarily metabolic disorders such as obesity, type 2 diabetes, and dyslipidemia in elderly populations. This raises a concern: are these sensitive populations, indicating a more serious underlying issue the rest of society is experiencing?
In the 1950s the Circadian Resonance Hypothesis was proposed by Pittendrigh and Bruce and published in Nature. This stated that an organism’s overall fitness is proportional with the coupling of its internal circadian rhythms to its surrounding environment. While very few studies exist focusing on the impacts of artificial lights and light pollution on human health, many do exist focusing on the negative impacts on the ecosystem, biodiversity, and wildlife. Need I remind everyone reading this, humans do not exist in an isolated vacuum from the ecosystem and are in fact likely experiencing ill effects much like any other mammalian member, though our niches within that ecosystem may vary.
As I consider my future living in another city where light pollution drowns out the stars leading me home, I begin plotting my respite escapes for the sake of my own health. What more can I do until policies change and we find alternative solutions that let us turn down the lights?
Thanks for taking the time to read my writing! If you enjoyed this essay, please take a moment to like, share, and/or comment. It helps others find it and read the scientific articles I’ve linked.