All across the UK we’re seeing street lights and outdoor lighting being retrofitted with new environmentally friendly LED lights. Traditional HPS (High Pressure Sodium) and Metal Halide lamps are being replaced in a bid to green up our cities and protect our environment.  

While it’s true that LEDs are far less energy consumptive than older forms of lighting – allowing some local councils to reduce fuel spending by as much as 50% on street lighting – they can come at a cost, both to our environment and to ourselves. 

How LED Lighting Affects Health

Bright white LEDs like those often being installed to light our cities have a much higher percentage of blue light than traditional incandescent bulbs.

This blue light has a proven side effect of inhibiting the production of melatonin in humans and animals. Melatonin is the chemical responsible for regulating sleep and wake cycles, and lowered levels of melatonin leads to disordered and dysregulated sleep. We know that poor sleeping habits can promote a variety of chronic health issues such as heart disease and diabetes.

With the replacement of warm incandescent lighting with blue and bright white LEDs across the UK there is the potential for some of these health issues to become even more widespread. 

The Environmental Impact of LEDs

The damage of blue light is not limited to humans, and can have a strong impact on animal and insect life.

Researchers have found that moths and caterpillars are found with 52% less frequency in hedgerows lit by LED lights than in unlit areas. This is compared to 41% in hedgerows illuminated by sodium lighting.

This drop in insect populations has a knock on effect on other species, including hedgehogs and small mammals who are detected less often in areas with bright LED lights.

Bright LED lighting can also affect song birds, who themselves have their sleep and wake cycles disturbed by these bright lights, singing earlier in the morning, and later at night. 

The Risk of Light Pollution

The effects of this light pollution are wide reaching, and stretch far beyond our cities and hedgerows, cutting off our connection with the night sky.

LEDs are brightening the night sky at an ever increasing rate. In 2016 astronomers reported that the milky way was now obscured at night to ⅓ of the human population.

With current estimates claiming that our night sky is brightening by 10% per year it’s even possible that in 20 years time almost all major constellations will be largely invisible to most people.

While this may not seem of utmost importance in a time of climate change, the cultural loss of a disconnection from the heavens is huge, and would lead to further environmental apathy. How are we supposed to care about the wider environment if we are so disconnected from it? 

Aside from its astronomical and cultural impact, the brightening of the night sky has serious environmental consequences, with many nocturnal animals such as sea turtles and migrating birds navigating by moonlight. 

So Why Choose LED Lighting?

All is not doom and gloom with LED lighting. When used thoughtfully, it can be a versatile tool to illuminate our cities in safe, sustainable ways.

In fact, when implemented correctly, LEDs offer more opportunities to reduce light pollution than traditional lighting methods.

Smart Uses for LED Lighting

In some areas where native bat populations need to be protected such as cycle paths and walkways local councils can create nocturnal corridors with lights of adaptable colour intensity. Research suggests that warm coloured light is far less disruptive to animals than white or blue light. So when pathways are not in use by humans, lights can give off a soft red glow and when sensors detect human movement the lights are intensified to allow safe passage, returning to a soft animal friendly red glow when the pedestrian or cyclist has passed. This can be achieved with the use of sensors and dimmers. 

It is even possible to synchronise the colour temperature of LED lights with the seasonal needs of local insect and animal populations.

Brands like Selux have developed dynamic red-white lighting systems that change over the course of the year, adapting to the rhythms of insects and surrounding biodiversity. In colder months, when Insects are not active, more powerful 2700k colour lighting can be used.  In summer, when wildlife is more active, softer red lights can be employed to minimize disruption to behavior and habitats.

Specific colour temperatures and wavelengths are less light polluting than others.

In the Pyrenees, the ski town of La Mongie had its street lights replaced by LEDs with a colour temperature of 2700k. This limited the amount of blue light that was interfering with a nearby observatory and allowed for darker skies to be enjoyed by all in the surrounding area.

Reducing Negative Effects of LED Lighting

Light shade systems use physical barriers or reflective surfaces to contain light beams so that light only permeates intended areas. These systems effectively prevent the pollution of the light upwards and out by casting a precise downward beam, protecting dark skies while still providing needed visibility to our urban spaces. 

Handrail and low-level lighting offer another solution to curb light spill. By illuminating pathways with lights at ground level, these systems light the areas needed for navigation while leaving other spaces undisturbed in darkness.

This approach helps preserve dark zones for wildlife and maintains a natural ambiance, striking a balance between safety and ecological sensitivity. 

Even simply using less bright LEDs can have positive and wide reaching effects on light pollution and wildlife protection.

Where possible light should be no brighter than it needs to be, providing light where needed, yet not overpowering and eradicating darkness. 

LED Lighting: The Big Picture

Despite LEDs potential risk to health and the environment when used in ways that are thoughtful and holistic they can be a powerful and ecologically friendly technology.

Rather than installing intensely bright blue light street lamps (even at a low carbon running cost) there needs to be more emphasis placed on specific wavelengths of light and creative lighting solutions, to allow for light and dark, the wild and the developed to coexist in our cities. 

Balancing the Pros and Cons of LEDs:

• Potential downsides: LED lights may cause hormonal disruptions, contribute to light pollution, and impact the environment.
• Mitigation strategies:
  • LEDs can be adjusted to specific color temperatures to minimize health and environmental effects.
  • Timers and sensors can help control when LEDs are on, reducing unnecessary energy use.
  • Low-level lighting can focus on specific areas, limiting light spill.
  • Light shields can contain and direct LED light to prevent light pollution.