To the residents of certain neighbourhoods in Hong Kong, it may seem as if the nights are just getting brighter and brighter, with eye-popping LED advertising panels, colour-saturated neon signs and floodlit billboards illuminating the streets, adjacent buildings and the night sky all around.
Although the bright lights promote the image of a modern and vibrant cosmopolitan city, they may be adversely affecting the daily lives and health of those living amid the glare in the city's high density commercial-cum-residential areas.
'In the past couple of years, the light pollution issue has got more serious in the urban jungle,' says Edwin Lau Che-feng, a local director of environmental group Friends of the Earth.
'There are more and more advertising spotlights, panels and big screens being put up in different parts of the city. The government has received many complaints from the public about [external] lights shining through their windows and curtains.'
Last year, the Environmental Protection Department (EPD) received 361 complaints about external light installations that were the responsibility of private organisations - mostly about light nuisance caused by advertisements, decorative lighting, or spotlights directed on building facades. The number of complaints has increased dramatically over a five-year period; even in 2007, 40 had been a seven-year high. And of course, many others suffer in silence.
'To be fair to the city, they have resolved a lot of the complaints,' says Carl Gardner, director of the London-based CSG Lighting Consultancy. Local authorities invited Gardner in October to conduct training seminars on practical lighting improvements based on British legislation.
Gardner says the local authorities have been going out to complainants and those responsible for the lighting to reach an informal solution, 'but they were starting to find it overwhelming because the number of complaints has increased exponentially'.
In response to the growing problem, the EPD established a task force of advisers from various professional bodies - environmental groups, advertisers, property developers, lighting designers and engineers - to set up technical guidelines to minimise light nuisance and energy waste. The six-page document, 'Guidelines on Industry Best Practices for External Lighting Installations', was released in January (available at the Environment Bureau's website www.enb.gov.hk ).
According to EPD information officer Chau Yau-fai, copies of the guidelines will be given to the offending parties when handling light nuisance complaints and compliance encouraged. 'Among other things, [the EPD task force] will consider whether a voluntary or a mandatory approach should be taken to regulate external lighting installations,' he says.
The voluntary nature of the new guidelines has its limitations, says Gardner. 'Hong Kong doesn't want to go down the legislative route, but if you don't have any sticks, then you need carrots to incentivise advertisers through subsidies on equipment or tax breaks. Otherwise, you won't get any change.'
In 2007, Dr Jason Pun Chun-shing, professor of observational astrophysics at the University of Hong Kong, began a light pollution survey in the city funded by the Environment and Conservation Fund. Having collected half a million data points, Pun found that the night sky in urban areas was many times brighter than in rural areas, even when measured on the same night with identical weather conditions.
'Unfortunately, in urban locations we don't achieve a good night sky until very late in the evening,' says Pun. 'City lights should be turned off around 11pm or so, but we still have a lot of lights around 1am, mostly unnecessary.'
Light pollution is defined as light seeping into the night sky, creating an aggregate halo effect over the city. It is barely noticed by most urban dwellers, but may have manifold environmental effects from the waste of energy to changing the ecological lifestyle of nocturnal animals and plants.
Unlike many other cities, Hong Kong's commercial and residential zones are not strictly separated. 'In places like Causeway Bay, Mong Kok or Wan Chai, you might see 30 big spotlights shine on an advertising board and just above it would be residential flats,' says Friends of the Earth's Lau.
In several cases, tenants have complained that the lights actually penetrate through curtains and make it difficult for them to sleep. Because no real studies have been conducted specifically on the health effects of this light trespass, it is difficult to prove any direct danger. There are, however, serious consequences when light at night causes disruption of sleep.
David Blask, professor of structural cellular biology at Tulane University in New Orleans, is a leading expert on the link between cancer and light at night. In 1987, he read a paper published by Dr Richard Stevens, an epidemiologist, hypothesising that electrification in industrialised societies may account for the elevated risk of breast cancer, which is roughly three to five times higher than in less developed countries.
At the time, Blask was conducting groundbreaking research on the hormone melatonin and its ability to combat cancer.
'The literature was quite solid showing that light at night would shut off melatonin production,' Blask says. 'If you put animals on constant light, the tumours would grow faster. [Stevens] put the experimental work in a context never considered before. The possibility that light at night, which is so prevalent in a 24-7 society, could be a cause of breast cancer by suppressing melatonin is an intriguing and important idea.'
Melatonin is a powerful antioxidant that can prevent mutations by stimulating DNA repair. It also blocks tumours from taking up linoleic acid, which is 'the king of pro-inflammatory fatty acids' and provides the fuel for tumour growth, Blask says.
The body is run by an internal clock that's synchronised by light. Darkness - usually around 9pm - triggers the production of melatonin via the pineal gland in the brain. Light deactivates the pineal gland and stops production of melatonin.
Since 1993 Blask has teamed up with colleague Robert Dauchy, who pioneered a method to inject and grow human tumours in rats. In one experiment, some rats were kept in a facility with a light leak at night.
'We noticed that the tumours were growing much more rapidly in these animals than in the control animals,' says Dauchy.
They suffused human tumours in rats with blood from volunteers at three different times - daytime, at nighttime and after being exposed to 90 minutes of light at night. They found that tumour growth proliferated with the daytime and light-at-night blood whereas the melatonin-rich nighttime blood shut down the tumour.
They also conducted light box experiments in which implanted female rats were kept under light of varying intensities. The brighter the light, the faster the tumours grew.
'Melatonin puts cancer cells to sleep at night,' says Blask. 'Without melatonin, they are awake 24 hours a day.'
A 2005 study, by epidemiology Professor Scott Davis of the Fred Hutchinson Cancer Research Centre in Seattle, Washington, established the link between night-shift work and an elevated risk of breast cancer.
Lau suggests light nuisance could be minimised through mandatory curfews like noise control ordinances.
'There should be a time for advertisers to stop shining their spotlights. In different districts, lights may be turned on until 3am. No one is doing any more shopping once they close at 10.30pm, so why do you need all that advertising?'
To Gardner, the solution is to regulate design principles. 'I've seen signs where 50 per cent or more of the light is spilling across the street. This is the wrong way to do it; with the right technique, you can position the light on the sign with no light spilling on the street,' he says.
He also suggests dimming the LED lights atop buildings so that the glare does not exceed a limit in square metres. 'The city once had quite a good skyline,' says Gardner. 'But what you notice more and more are the really, really bright building signs - one overpowering the other, with just so many bright spots. It's quite garish. There is no sense of balance over the city.'
But Pun disagrees: 'In this city, brightness means prosperity.'
In a 2010 survey by the Advisory Council on the Environment, 70 per cent of 2,700 respondents felt that light pollution existed in Hong Kong, but 78 per cent said lights helped beautify the environment and promoted the city's image.
In other words, most Hongkongers like the bright lights, so change may be a challenge.