Mexico City Moves to Regulate Light Pollution

The Mexico City Congress has approved an initiative to reform and add various provisions to the Environmental Law for the Protection of Land in the Federal District concerning light pollution. A new transitional article was also approved, requiring the city’s Ministry of Environment (SEDEMA) to begin drafting an environmental standard that will establish maximum permissible levels of artificial light and regulate its emissions. The agency must also define procedures to monitor light pollution and determine which establishments will be subject to regulation.

Jesús Sesma Suárez, Legislator who introduced the proposal, explained that this type of pollution is mainly generated in large cities and industrialized zones due to artificial light sources that alter the environment, causing harm to both ecosystems and human health. He added that this new legal framework will require the Single Environmental License to include a program for the use, regulation, and control of artificial and intrusive light, in accordance with the new environmental standard.

According to UNAM, light pollution is defined as luminous flux from artificial sources that increases the brightness of the night sky. Globally, 83% of the population lives under polluted night skies to varying degrees, a figure that rises to 99% in Europe and North America. Moreover, specialists estimate that light pollution increases at a yearly rate of 2%. 

The effects of this phenomenon on human health are diverse. Raúl Aguilar, Researcher, UNAM’s Institute of Cellular Physiology, Division of Neurosciences, explains that nighttime exposure to intense light inhibits the secretion of melatonin, the hormone responsible for regulating the sleep-wake cycle. Moreover, exposure to strong light at night alters several brain functions, leading not only to insomnia but also to mood disorders during the day.

More severe consequences have also been documented. A study by the American Heart Association revealed that greater exposure to artificial light at night is associated with a 35% increase in heart disease risk over five years and a 22% increase over 10 years.

Researchers analyzed the health of 466 adults with an average age of 55 who had undergone CT scans between 2005 and 2008. They compared participants’ brain scans and health outcomes with their exposure to artificial light based on the orientation of their homes. Results showed that higher levels of artificial light were linked to brain stress activity and inflammation of blood vessels.

“Even modest increases in nighttime light were associated with greater brain and arterial stress. When the brain perceives stress, it activates signals that can trigger an immune response and inflame blood vessels. Over time, this process can contribute to the hardening of arteries, raising the risk of heart attacks and strokes,” explained Shady Abohashem, lead author of the paper.

Nighttime intrusive light has also been linked to disorders of the autonomic nervous system, such as hypertension, obesity, diabetes, and even cancer. “The connection to cancer has been found at the genomic level because some of the genes that regulate the cell cycle, which go haywire in cancer, are connected to those that generate and maintain circadian rhythms, known as clock genes,” Aguilar said.

This phenomenon also has severe consequences for wildlife and ecosystem dynamics. In birds, for instance, light pollution disrupts migration patterns. Many species migrate at night and become disoriented by artificial light, leading them to collide with buildings, lighthouses, oil platforms, and ships, causing high mortality and exhaustion rates.

These disruptions to biological cycles may even have direct consequences for climate change. A study published in Nature Climate Change found that artificial nighttime light subtly alters the natural balance of carbon cycles. The research focused on 86 sites across North America and Europe, using satellites and carbon flux monitoring to evaluate ecosystem behavior.

Researchers discovered that nighttime light pollution increases ecosystem respiration, meaning plants, microbes, and animals release more carbon dioxide. However, there was no equivalent increase in photosynthesis, the process by which plants remove carbon from the atmosphere.

“This is a widespread issue that is changing how ecosystems function, disrupting energy flows, animal behavior, habitats, and natural patterns. In short, brighter nights mean more carbon emissions, a troubling sign for our planet,” stated Alice Johnston, Researcher, Cranfield University who led the study.

The authors noted that this problem could be easily reversed through better lighting design, including the adoption of adjustable, directional, and sensor-based lighting technologies. Lighting accounts for over 15% of global electricity consumption, so reducing it would also help cut the sector’s climate impact. “Fighting light pollution represents a rare triple win for the environment, energy efficiency, and human well-being,” Johnston added.

Several countries have already taken steps to address this issue. In Europe, France, Croatia, Slovenia, and the Czech Republic have enacted laws limiting light pollution. Meanwhile, others, like Austria and Ireland, have issued nonbinding guidelines. In Latin America, Peru recently approved the regulations for the Law on the Prevention and Control of Light Pollution, establishing a technical and legal framework to mitigate the negative effects of excessive artificial light on people, wildlife, and ecosystems.