# LEDs and Health: New Findings Validate Long-Held Concerns
For many years, worries have been voiced regarding the possible health impacts of LED lighting, including those in smartphone screens. Recent groundbreaking research from the Pacific Northwest National Laboratory (PNNL), a national lab under the U.S. Department of Energy, has validated that LEDs can indeed pose health risks. This discovery has reignited discussions about the extensive use of LED technology and its effects on human health.
## The Issues with LED Lighting
LEDs (light-emitting diodes) have become widespread in contemporary life, ranging from household lighting to smartphone displays. They are energy-efficient, durable, and cost-effective. Nevertheless, the mechanism by which LEDs operate—by rapidly switching on and off—can produce flickering that, while not noticeable to the naked eye, can still affect human health. This flickering is frequently attributed to a technology known as **Pulse Width Modulation (PWM)**, which alters brightness by changing the duration the LED remains on during each cycle.
Although numerous LED products claim to be “flicker-free,” this phrase can be misleading. It generally indicates that the flicker isn’t visible to the human eye, yet research indicates that even undetectable flicker can lead to considerable physiological and neurological consequences.
## Significant Insights from the PNNL Study
The latest research from PNNL illuminates the health hazards linked to LED flicker. The study assessed 85 various light waveforms, including those typically found in LED lighting and smartphone screens. Participants, consisting of individuals prone to migraines and those without a migraine history, were exposed to these waveforms in a controlled setting.
### Key Insights:
1. **Health Reactions**: Up to 64% of participants indicated they experienced headaches, eye strain, and disorientation after exposure to common flickering LED lights. Even among non-migraine sufferers, 17% reported similar experiences.
2. **Annoyance Level**: The study analyzed the “mean annoyance rating” of various light waveforms on a scale from 0 (not annoying) to 8 (extremely annoying). The rectangular waveform with 100% modulation at 400Hz—similar to that used in many popular smartphones—received a score of 4.8, rendering it one of the most concerning waveforms.
3. **Phantom Array Effect**: The research underlined the “phantom array effect,” a situation where flickering lights generate a series of repeated images when the eyes move swiftly. This effect, which is more marked in LED lighting, contributes to discomfort and visual strain.
### Importance of PWM
The frequency of PWM flicker is a crucial element. Most contemporary smartphones, including those made by Samsung, Apple, and Google, utilize PWM frequencies ranging from 240Hz to 480Hz. Although these frequencies are sufficiently high to avoid visible flicker, they are still low enough to trigger health issues. Research indicates that PWM frequencies should ideally be at least 2400Hz to lessen negative effects. Some brands, such as Vivo, have already embraced higher PWM rates, significantly lowering the risk of eye strain and associated symptoms.
## The Significance of Smartphone Displays
The results are particularly alarming for smartphone users, as displays serve as a primary source of LED exposure. The transition from LCD to AMOLED screens, which depend on LEDs, has intensified the issue. For instance, Apple’s iPhone X, the initial iPhone featuring an AMOLED display, coincided with a surge in user complaints about eye strain and headaches.
While certain manufacturers have made gradual improvements—Samsung and Apple have raised PWM frequencies to 480Hz—these adjustments do not adequately tackle the underlying issue. Conversely, companies like OnePlus and Motorola have adopted **DC dimming**, a safer alternative to PWM that completely eliminates flicker.
## The Research on Flicker Sensitivity
PNNL’s study also challenged the long-established belief that flicker sensitivity is purely a visual concern. Instead, it emphasized the **phantom array effect**, which occurs when the eyes quickly traverse a flickering light source. This effect is not captured by conventional flicker measurement standards, which concentrate on the stroboscopic effect (whether the flicker is visible when the light source is static).
The findings indicated that individuals prone to migraines are more likely to notice the phantom array effect and exhibit increased sensitivity to flicker. However, even those without migraines reported discomfort, highlighting the widespread nature of the issue.
## Moving Forward: Necessary Changes
### For Manufacturers:
1. **Implement Higher PWM Frequencies**: Raising PWM frequencies to at least 2400Hz can greatly mitigate health risks. Brands like Vivo have already set a precedent by meeting this standard.
2. **Transition to DC Dimming**: DC dimming is a safer alternative to PWM and is already in use by manufacturers such as OnePlus and Motorola. This technology eliminates flicker by modulating the voltage supplied to the LEDs instead of rapidly toggling them on and off.
