The LED problem nobody talks about

In 2014, the Nobel Prize in Physics was awarded to the inventors of the blue LED. The Nobel Committee called it a technology that "will contribute to the saving of enormous amounts of energy." They were correct. The transition from incandescent and fluorescent lighting to LED has been one of the most successful energy transitions in history — dramatically reducing electricity consumption and carbon emissions globally.

What the Nobel Committee did not mention — and what most public discourse still ignores — is that the same spectral property that makes LEDs so efficient (their bright, blue-shifted emission) also makes them biologically disruptive in ways that incandescent bulbs never were. The energy revolution came with a circadian cost that is only now being systematically quantified.

Why LEDs are spectrally different from older lighting

Incandescent bulbs work by heating a tungsten filament until it glows. The light produced follows a blackbody radiation curve — heavily weighted toward red and infrared wavelengths, with relatively little blue. The colour temperature of a standard incandescent is approximately 2700K, and the spectral distribution resembles, in a rough way, candlelight or firelight — the light sources human biology evolved alongside for hundreds of thousands of years.

Compact fluorescent lamps (CFLs) moved somewhat toward the blue end of the spectrum. But LEDs are categorically different. White LEDs are not actually white — they are blue LEDs coated with a yellow phosphor that converts some of the blue light to longer wavelengths. The residual blue peak is sharp, intense, and sits squarely at 450–470nm — the range that maximally stimulates melanopsin in the ipRGC retinal cells responsible for circadian signalling.

The 2016 AMA warning that went largely unheard

In June 2016, the American Medical Association adopted a formal policy statement on the health effects of high-intensity LED street lighting. The AMA stated that these lights have "five times greater impact on circadian sleep rhythms than conventional street lamps" and warned of potential health consequences including "discomfort, disability glare, and potential public health impacts including increased risk of cancer, cardiovascular disease, obesity, and diabetes."

This was not a fringe position. It was the official policy of one of the world's largest and most respected medical organisations, adopted after review of the accumulated peer-reviewed literature. It received minimal mainstream media coverage. LED adoption accelerated. The AMA warning was largely forgotten outside specialist circles.

Indoor LED lighting: the overlooked exposure

Most public attention on blue light focuses on screens — phones, laptops, tablets. This is understandable, as screens are held close to the face and are explicitly interactive. But the contribution of indoor LED lighting to circadian disruption is substantial and systematically underestimated.

The typical modern Indian home or office is lit with 4000K–6500K LED overhead fixtures — a colour temperature chosen for its "daylight" quality that enhances perceived brightness and alertness. At these colour temperatures, the blue emission peak is pronounced. A person sitting in a room lit with 6500K LEDs at 200 lux — a typical indoor lighting level — is receiving significant circadian-alerting blue light even if they are not looking at any screen.

The outdoor ALAN problem: a global public health emergency

Artificial Light At Night (ALAN) from outdoor sources — street lighting, commercial signage, building illumination — has been increasing at approximately 2% per year globally. The transition to LED street lighting has compounded this by shifting the spectral composition of ALAN toward the blue-heavy range that maximally disrupts circadian biology.

Research published in Science Advances found that ALAN exposure is associated with significantly increased rates of breast cancer, prostate cancer, obesity, diabetes, and cardiovascular disease at the population level. A study of 500,000 people in Spain found that those living in areas with high outdoor artificial light had 1.5 times higher odds of breast cancer and 2.1 times higher odds of prostate cancer compared to those in darker areas.

These are dose-response relationships — the more light exposure at night, the greater the risk. And the risk is not theoretical. The World Health Organisation classifies night-shift work (which involves high ALAN exposure) as a Group 2A carcinogen. The mechanism — chronic melatonin suppression disrupting cell cycle regulation and immune surveillance — is increasingly well understood.

The Indian context: why this matters more here

India's LED transition has been among the fastest in the world, driven by the UJALA scheme which distributed over 360 million LED bulbs between 2015 and 2020. The energy savings have been significant. But the circadian consequences have been entirely absent from public health discourse.

Indian households that replaced warm incandescent bulbs with cool 6500K LEDs — the most common variety distributed at subsidised rates — made a meaningful shift in their evening light environment without any awareness of the biological implications. A family sitting under 6500K LED overhead lighting from 7 PM to 10 PM is receiving a sustained circadian-alerting signal throughout the critical melatonin onset window.

Combined with India's already high smartphone penetration (600+ million users) and long average daily screen time (5+ hours), the cumulative blue light burden in the evening hours is substantial. India's consistently low average sleep duration (6.5 hours, among the lowest globally according to Fitbit and similar large-scale datasets) is almost certainly partially attributable to this light environment.

What can actually be done

The solutions operate at multiple levels, from individual to systemic.

At the individual level: Replace overhead LED bulbs in living spaces and bedrooms with 2700K warm white equivalents. Install dimmer switches — lower lux in the evening significantly reduces circadian impact even at the same colour temperature. Wear amber-tinted glasses after 7 PM to filter residual blue wavelengths from any remaining light sources and screens. These three interventions, combined, create an evening light environment that is substantially more circadian-compatible than the default modern home.

At the systemic level: Cities and municipalities should adopt warm-spectrum LED street lighting rather than the 4000K–5000K products currently favoured. Some European cities — including Amsterdam and Paris — have begun this transition, explicitly citing circadian and ecological health impacts (blue-shifted street lighting also disrupts wildlife circadian systems and reduces biodiversity). India's rapid urbanisation makes this a significant public health opportunity if addressed proactively.

The screens and lights together

It is important to understand that screens and ambient lighting are additive sources. A person using a smartphone in a room lit by 4000K LEDs is experiencing blue light from two sources simultaneously. Reducing one while ignoring the other produces incomplete benefits. A comprehensive approach addresses both: warm the room lighting and filter the screen light.

This is why After7 amber glasses work even when the room lighting has not been changed. They address the direct retinal input from screens and partially compensate for ambient light through the filtering effect. But combining glasses with warm room lighting produces a substantially better result — the amber lenses handle what the room lighting cannot, and vice versa.

Sources

American Medical Association (2016). AMA adopts guidance to reduce harm from high intensity street lights. AMA Policy Statement H-135.927. · Falchi, F. et al. (2016). The new world atlas of artificial night sky brightness. Science Advances, 2(6). · Kloog, I. et al. (2009). Global co-distribution of light at night and cancers of prostate, colon, and lung in men. Chronobiology International. · Garcia-Saenz, A. et al. (2018). Evaluating the association between artificial light-at-night exposure and breast and prostate cancer risk. Environmental Health Perspectives. · Ministry of Power, India. UJALA scheme: Annual Report 2020.