Health and wellness

How light pollution is a real health issue and five things you can do to reduce it

Hong Kong’s illuminated skyline is famous, but it could be bad for your health. Parts of the city at night are 1,000 times brighter than the global average. We share tips on how to lessen the unbearable brightness of being

PUBLISHED : Tuesday, 12 December, 2017, 6:46am
UPDATED : Tuesday, 12 December, 2017, 6:04pm

Our world is a brighter place – and not in a good way. According to Dr Jason Pun Chun-shing from the University of Hong Kong’s Department of Physics, whose work involves gauging the level of light pollution, Hong Kong ranks among the worst on the planet. A 2013 study by the university’s scientists found the city’s urban night sky to be as much as 1,000 times brighter than international norms.

A study of global satellite images suggests the entire night time face of the Earth is getting too bright – especially in places where wealth and urbanisation are expanding, such as China.

That brightness – estimated to be growing at 20 per cent a year in some parts of the world – may be doing significant harm to our health. Eighty per cent of the world’s population has never even seen the Milky Way.

While it’s clear that light at night is important, the value of darkness – true darkness – is often forgotten. As Steven Lockley of Harvard Medical School’s Division of Sleep Medicine reminds us, it is essential to the healthy biological function of most living things – the flick of a switch interferes with mating, moving and migrating patterns.

Pun agrees, referring to light pollution as “environmental degradation, which affects the natural environment and the ecosystem”.

In humans, light at night suppresses the production of melatonin, a hormone that helps promote healthy sleep patterns and is believed to protect against tumour growth. Being exposed to light at night has been linked with increased risk for diabetes, sleep disorders, and even obesity.

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So how can we protect ourselves, our world and promote a little darkness? Pun says that most “light pollution is caused by excessive artificial outdoor lighting, such as street lamps, neon signs, and illuminated signboards”, and adds that “any improvement in the lighting would benefit the community”. This could take the form of reduced intensity, or adjusting the direction of lighting to the specific area it is needed, and applying proper shielding.

Kevin Gaston, a professor of biodiversity and conservation at the University of Exeter in Britain, specialises in the ecological impacts of artificial nighttime light. In the Journal of Applied Ecology, he and his team of researchers suggest five bright ideas to dim the lights.

1. Start with the light switch. The most obvious, most effective and most economical way to reduce light pollution is to start turning lights off. Even outside lights at night can be turned off when you go to bed: there’s little evidence to support the notion that exterior lighting reduces crime.

2. If you must keep outside lights on, consider replacing bright ones with a low-glare variety, or installing motion sensors on lights. Lighting on demand trumps a manual switch and will pay for itself in savings on electricity bills.

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3. Limit device use at night. Virtually impossible? No, for your health’s sake, switch off that smartphone. The consensus is that the blue light that LED screens emit can slow or even halt the production of melatonin (which is why you’re not sleeping well after late-night computer use). You could adjust device settings to dull the brightness, but your eyes, your mind, and your partner will all benefit from a break. Read a book. Write a handwritten note. Have a real-life conversation over a candlelit dinner, a perfect precursor to a good night’s sleep.

4. The simple act of shielding our lights – or directing light towards its intended target – is one way to control light pollution. Pun agrees. “If we can … use better design to direct the lighting at a better angle and use the right amount of light, we can reduce a lot of light pollution,” he says. Think anglepoise lamps and elegant light shades, and install heavy curtains or blinds to stop street lights bleeding in – called ‘light trespass’.

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5. Campaign locally for kinder night lights. To promote dark sky preservation, Pun’s team at the university is running a “Be a responsible stargazer – Enjoy the meteor shower” campaign, aimed at creating an awareness of light pollution while simultaneously promoting light-pollution reduction and encouraging the healthy habit of stargazing.

People can post photos showing lighting fixtures which cause, or reduce, light pollution (with location) to Facebook with the hashtag “#ResponsibleStargazer. The organisers will select the best posts and showcase them during the Hong Kong Science Festival at the Hong Kong Science Museum in March. Details of the campaign can be found at

Now, enjoy the darkness. Don’t be scared of it. Rarely is the night completely black: there is moonlight, stars offer pinpricks of light and ... oh wait ... is that the Milky Way?