The Dark Side Of Bright Lights In India

On a routine drive between Madhya Pradesh’s Jabalpur city and the forest, Nikita Khamparia, a naturalist, often finds herself blinded, not by dust or fog, but from the glare of LED headlights. Once a smooth commute, it has now turned hazardous, as high beams from vehicles force her to hit the brakes and wait for oncoming cars to pass by, before she can continue with her journey.

Experts warn that this is a sensory hazard on the road. Drivers around the world have reported the same sensory experience, which, in some cases, ends in a crash.

“For the same reason that the sunset appears red, colours with shorter wavelengths scatter earlier, while longer wavelengths travel farther, blue light scatters more in the human eye than red, consequently by a factor of ten to one,” says Dr. Mario Motta, a cardiologist and amateur astronomer, who helped shape the American Medical Association’s (AMA) policy on light at night. “The disability glare increases exponentially as you get older.”

Experts note that increasing artificial lighting is disrupting human health, wildlife, and ecosystems.

The use of LEDs has public health and ecological consequences. Blue light is a well-known suppressor of melatonin, the sleep hormone. A Harvard study found it was twice as effective as green light. In another experiment, just two hours of exposure to an LED tablet reduced melatonin by 55%, and shifted circadian rhythms by 1.5 hours, compared to reading a book under low light.

“Every additional amount of blue further reduces the production,” Dr. Motta adds, “and a disrupted circadian rhythm can lead to chronic fatigue syndrome, obesity, depression, and other psychiatric illnesses.”

When the body’s internal clock goes out of sync with its environment, it can impair critical functions like DNA repair, hormone regulation, metabolism, and the immune system, often leading to endocrine-related cancers. A large, multi-control study, found that exposure to outdoor artificial night at light (ALAN), especially in the blue spectrum, increased the risk of breast cancer by 47% and of prostate cancer by 105%. At least 24 different studies have concluded there’s a link, according to Dr. Motta.

But, humans are not the only species affected.

Up to 88% of sea turtle hatchlings, which rely on a moonlit horizon to navigate, end up crawling inland when there’s an artificial light source, and die. In one study, moth caterpillar abundance shrunk by 52% under LED street lamps, in comparison to unlit areas. Bat-foraging reduced dramatically near white LEDs, leading to fewer fruits per plant, while over 70% of moths were drawn away from flowering plants towards street lamps, and bees’ sleep patterns were disrupted. With a few exceptions, artificial blue light is also a threat to pollinators, whose decline can, in turn, affect global food security.

Iain Macrae, a UK-based lighting design expert and consultant, says that warmer light comes with its own troubles, like snails and slugs in the garden. “While reducing blue content is an excellent start, the approach going forward should be lighting only when it’s needed.”

A century of warnings with little legal action

Astronomers first caught on to light pollution in the early 20th century. The Vatican Observatory was famously moved from Rome to the papal residence at Castel Gandolfo as the skyglow — the bright haze created when artificial lights scatter in the atmosphere — kept getting in the way of observations, and later to Arizona, U.S., for the same reason.

Over 95 years and several international recognitions later, “light pollution” has still to be legally defined in most countries, including India, where a large portion of the population lives under light-polluted skies,

The brightening of the night sky is traceable to an early form of artificial light, the gas lamp. It was only accelerated when electrical lighting was introduced and became a runaway problem as the light got bluer.

“Standardisation of lighting takes years to catch up with research,” explains Macrae, “and is heavily influenced by manufacturers. Just because photometry — the science of measuring visible light — does not yet reflect the human experience, or prove there is glare, it does not mean concerns should be ignored.

The cost of over-lit cities

While early LEDs were more efficient at a higher or “cold” correlated colour temperature (CCT), measured in Kelvins (K), that’s no longer true. They aren’t inherently bad either. LEDs far outshine older technologies at efficiency as very little electricity is converted into heat, and more into light. They also fare well on longevity, visibility, and recyclability compared to the older lights.

The overuse of LEDs is the concern. While at greater output it’s possible to light up an area with fewer light sources, the economies of LEDs ended up making them more accessible and have led to wider adoption instead. The shift from traditional bulbs to LEDs alone contributes to skyglow, even without the introduction of a single extra lamp. At 5100K, colloquially known as “daylight” or neutral white, an LED lamp produces nearly eight times more skyglow than a low-pressure sodium light, a 2014 study found.

The Indian urban lightscape is dominated by LEDs. Light pollution creates a dome of scattered light that obstructs our view of celestial objects. It sits over major population clusters. The bigger the city, the brighter and thicker the dome.

Shweta Kulkarni, a renowned dark-sky advocate and Fellow of the Royal Astronomical Society (FRAS), in July published a report, quantifying the rise in Maharashtra’s night sky brightness.

“In Pune, I now see the downside of every over-lit flyover,” said Kulkarni. Satellite data shows the city’s night sky has grown nearly 50% brighter in just over a decade, while Mumbai is already among the brightest in the country, she indicates. “Pune’s upward radiance leapt from 31.6 nW cm⁻² sr in 2012 to 47.4 nW cm⁻² sr in 2024, while Mumbai already blazes past 51 nW cm⁻² sr,” she specifies.

Kulkarni adds that India’s night sky brightness is increasing by 10% annually, about 2% faster than the global average, and erasing darkness itself, a resource that at least 60% of earth’s species depend upon.

Her research points out that skyglow is expanding across Maharashtra, driven by LED proliferation, rapid urbanisation, and growing tourism infrastructure.

“LEDs now account for about 99.80% of Mumbai’s street lights,” says S.N. Inchnalkar, Deputy Chief Engineer (Street Lighting), Brihanmumbai Electricity Supply and Transport Undertaking (BEST). Depending on the area’s specific lighting requirement, these lamps are either warm white (2700–3300K) or cool white (4500–5700K).

K.H. Perekar, Chief Engineer (Mechanical & Electrical), Brihanmumbai Municipal Corporation (BMC), adds that to mitigate the impact of LEDs, they now have smart, sensor-equipped lights that dim to a lower intensity during late night and early morning hours. “Due to law and order concerns, however, the rollout stays limited to some interior areas and administrative offices.”

Mumbai also has a centralised control system that allows for remotely turning lights on or off and monitoring technical faults. But for all these strides, there still isn’t a statutory spectral or luminance limit.

In Gujarat, a recent study found that over a decade, from 2013 to 2024, the radiance of night light increased by 60% in Ahmedabad, 45% in Surat and 41% in Vadodara. “From 2014 to 2023, all three cities show a consistent upward trend in radiance, with significant seasonal fluctuations observed from July to September due to monsoonal cloud cover,” noted the study. “These findings underscore the interplay between seasonal variability and long-term growth, highlighting the severity of light pollution in urban areas and emphasising the need for data-driven interventions to inform urban planning and resource management strategies.”

Bright LEDs can also cause glare and create blind spots. Kulkarni explains that modern LED car lamps can shine up to 10 times brighter than old halogens, but India has no glare limits like those set by the UN. Similarly, a single LED billboard can emit enormous brightness (90,000 lumens for a 50m² billboard), yet most municipal laws don’t set standards for it.

Outdoor lighting should not exceed 2200K, unless a specific colour rendering — how accurately a light source shows colours compared to natural sunlight — is necessary, according to Travis Longcore, ecologist and an adjunct professor at the UCLA Institute of the Environment and Sustainability, who coined the term “ecological light pollution”. “There’s no excuse for using 5000K outdoor lights except in extraordinarily limited circumstances such as professional sports stadiums during play,” he says. In addition, there are many well-established solutions for reducing excess runaway light, all workable with existing fixtures.

Darren Evans, professor of Ecology and Conservation, Newcastle University, and co-author of the study involving moth caterpillars, says, “We are confident that the detrimental impacts of LEDs in particular can be resolved through spectral tuning, in addition to shielding, dimming and motion sensor activation, an easy measure for providing only when it is needed, rather than emitting unnecessary light all night long.

(Published under Creative Commons from Mongabay India)