A study from Tel Aviv University found that artificial lighting at night, even at the intensity of street lighting, disrupts the activity patterns of the immune system in wild rodents and may increase the risk of mortality.
After previous studies showed that Artificial lighting disrupts the chirping of cricketsIt now turns out that mammals are not immune to its effects either.
New research from Tel Aviv University indicates for the first time that artificial lighting at night – even that of street lighting intensity – may disrupt the immune system of wild rodents, and even affect other mammals.
Hagar Vardi-Naim, a doctoral student in the New School for the Environment and the George S. Wise Faculty of Life Sciences, conducted the research inA. Sigles Zoological Research Garden At Tel Aviv University, under the direction of Prof. Yariv Wein – Head of the Applied Immunology Laboratory in the Faculty of Life Sciences – andProf. Noga Kronfeld-Shor – Head of the School of Environment and Rector, Tel Aviv University.
Hagar's goal was to examine how artificial lighting affects the immune system of mammals; the findings indicated that even minimal exposure to lighting at night increases the risk of mortality by 2.35 times.
A Matter of Time: The Importance of the Biological Clock to the Immune System
Overcoming jet lag after a flight isn't the only challenge to our biological clock.
According to Vardi-Naim, "large parts of our bodies – and those of all mammals – are regulated by a biological clock," which operates on a 24-hour cycle, "and is adjusted to the light and dark cycle." The clock "transmits to the various organs and systems what they are required to do at each hour," similar to the immune system.
Some of the levels of lymphocytes in our bodies – white blood cells that protect against infections, bacteria, and cancer cells – rise and fall, and as a result, more antibodies are produced against bacteria or viruses at certain times.
"The body needs to know what time it is. Light pollution changes the natural regime of light and darkness, disrupts the adjustment of the central clock to the environmental time and changes these patterns, so that time no longer has much meaning."
Rodents in the dark and light: Antibody production at night
The study involved two species of small rodents living in the Judean Desert and the Negev: the golden skunk, which is more active during the day, and its cousin the common skunk, which is more active at night.
Both species of rodents were housed in “environmental conditions that mimicked natural conditions as closely as possible,” with half of the enclosures illuminated with white LED lighting—“the most common lighting today, and at a relatively low intensity—that simulates street lighting.” The control group was left in dark conditions subject to changes in natural light, such as the sun, moon, and stars.
The researchers examined the percentage of white blood cells in the rodents' blood at several time points during the day, and discovered that, like in humans, their lymphocyte levels increase during the resting hours between two and four in the morning.
The amount of antibody production in response to an antigen (a substance that the immune system recognizes and reacts to) is a time-dependent process; therefore, "animals exposed to the antigen during resting hours produce much more antibodies against it than those exposed during active hours."
The Effects of Light Pollution: From Rodents to Humans
The research team found that exposure to light pollution at night blurred the body's antibody production patterns: "Instead of a cycle of peaks and troughs in the percentage of lymphocytes in the blood and in the immune response, we saw a complete flattening of the daily patterns." The flattening refers to the immune system losing touch with the biological clock, and in essence "may respond less optimally to infections and environmental stress or vaccination, a situation that could make animals more vulnerable over time."
The researchers speculate that the disruption of biological timing in the rodents contributed to the decrease in survival, as higher mortality rates were recorded in the animals exposed to light pollution.
The research team sees the fate of the thorns as merely an illustration – and that “light pollution should be considered as an environmental health risk with broad implications – not only for wildlife but also in the context of human health and the entire ecosystem.”
Additionally, those animals with weak immune systems may transmit their diseases to humans, thereby affecting human immune systems; therefore, the research team "highlights the need to reexamine the extent and intensity of nighttime lighting in urban and open spaces."
It is possible that reducing nighttime lighting will help restore the natural balance – and strengthen the immunity of mammals, including humans.
More of the topic in Hayadan:
