She continued, \u201cFor example, the levels of certain white blood cells rise and fall in the blood, and the body produces more or less antibodies at specific times. Such oscillations can enhance the immune response to bacteria or viruses, but for this, the body must know the time.\u201d<\/p>\n
She continued, \u201cLight pollution alters the natural light-dark regime, disrupts the central clock\u2019s synchronization with environmental time, and changes these patterns, rendering time almost meaningless.\u201d<\/p>\n
\t![\"\"](\"https:\/\/www.europesays.com\/iran\/wp-content\/uploads\/2026\/04\/1280px-Arabian_Spiny_Mouse-640x400.jpg\")
\n\t\tA spiny mouse. (Broobas, CC BY-SA 4.0, Wikimedia Commons)<\/p>\n
The spiny mice were kept in enclosures that simulated natural environmental conditions as far as possible. Half of the enclosures were illuminated at night with white LEDs, the most common type of lighting used today, at a relatively low intensity to simulate street lighting.<\/p>\n
The control group was kept in natural light-dark conditions.<\/p>\n
The researchers measured the percentage of white blood cells, called lymphocytes, in the rodents\u2019 blood at several points during the 24-hour cycle.<\/p>\n
They found a pattern similar to the human rhythm, with lymphocyte levels in the blood rising during rest hours, between 2 a.m. and 4 a.m.<\/p>\n
They also discovered a clear 24-hour lymphocyte rhythm and found that the quantity of antibodies produced in response to an antigen (something that triggers an immune response) was time-dependent.<\/p>\n
\u201cWe saw that animals exposed to an antigen during their rest hours produced far more antibodies than those exposed during their active hours,\u201d said Vardi-Naim.<\/p>\n
\u201cExposure to light pollution, however, completely muddled these rhythms,\u201d she said. \u201cInstead of a daily cycle of peaks and lows in the level \u05ddf lymphocytes and immune response, we observed a complete flattening of the daily patterns. This means that the immune system loses its natural timing, and consequently, its response to infections, environmental stress, or vaccination might be less than optimal, possibly increasing the animals\u2019 vulnerability over time.\u201d<\/p>\n
Furthermore, extensive and rapid mortality was observed among the mice exposed to light pollution, with a 2.35 times higher risk of death compared to the control group. Vardi-Naim noted that even though the exact cause of death could not be determined, the rise in mortality occurred alongside disruption of immune and endocrine, or hormonal, rhythms, suggesting a likely connection between damage to biological timing and reduced survival.<\/p>\n
\t![\"\"](\"https:\/\/www.europesays.com\/iran\/wp-content\/uploads\/2026\/04\/2-640x400.jpeg\")
\n\t\tFrom left: Prof. Noga Kronfeld-Schor, Hagar Vardi-Naim, and Prof. Yariv Wine. (Tel Aviv University)<\/p>\n
She added that while the spiny mice in the study were only an example, the findings had implications for all living creatures, including humans.<\/p>\n
\u201cOur results show that artificial lighting at night is not merely an aesthetic environmental change, but an active biological factor capable of disrupting critical physiological mechanisms. Chronic exposure to artificial lighting at night disrupted the timing of the mice\u2019s immune and endocrine systems and impaired their survival under conditions that otherwise simulated the natural environment,\u201d she went on.<\/p>\n
\u201cWe believe that light pollution should be regarded as an environmental health risk with broad implications, not only for wildlife but also for human health and the ecosystem as a whole. Studies show that animals with weakened immune systems can transmit diseases to humans, and the human immune system may respond similarly. The study underlines the need to include biological considerations in lighting policies and to reexamine the scope and intensity of artificial lighting at night in both urban and open spaces.\u201d<\/p>\n
The study\u2019s supervisors, both also associated with the university\u2019s new Environmental School, were Prof. Yariv Wine, head of the Applied Immunology Laboratory at the School of Biomedicine and Cancer Research, and Prof. Noga Kronfeld-Schor, head of the Ecological and Evolutionary Physiology Laboratory at the School of Zoology, and rector of the university.<\/p>\n
The research, published in Environmental Pollution<\/a>, was supported by the Israel Science Foundation.<\/p>\n
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