Can we overcome the hazards and irritations of light and sound pollution? Duncan Graham-Rowe goes in search of the quiet dark.
Take a trip to Galloway Forest Park, 40 miles west of Dumfries, and like many tourists you'll discover 300 square miles of stunning Scottish woodland. Pay a visit at night and you'll find you're not alone. A growing number of these tourists flock to the area not for the stunning landscape, but rather for the very fact that none of the surroundings are visible.
That's because since 2009 Galloway has held the status of Dark Sky Park, the first in the UK, and only one of a handful of places around the world to receive recognition for how utterly devoid it is of artificial light pollution. As such, it's a magnet for amateur astronomers who are willing to travel great distances for a rare chance to see the stars without their view being impaired by the almost ubiquitous nightglow of civilisation.
While some people seek out darkness, others crave silence - an equally rare commodity in the 21st century. And sound and light pollution are not just aesthetic concerns: there's growing evidence that they can have a seriously damaging effect on the health of humans and ecosystems alike.
The World Health Organisation cites noise-induced hearing impairment as the single most prevalent irreversible occupational hazard, causing a disabling effect on 120 million people. Both light and sound pollution have also been linked to a range of seemingly unrelated diseases, from heart conditions and high blood pressure to cancer. There is even growing evidence that light pollution is playing a significant role in the rise in obesity - more of which later.
Meanwhile, they are taking their toll on wildlife, too. Brightly lit office buildings, for example, can confuse night-flying migratory birds, leading to collisions or starvation as they lose their way. And as if the odds aren't already stacked against their survival, newborn sea turtles can suffer a similar fate. During their night time dash for the sea, bright lights can confuse these hatchlings to the point that they end up crawling inland instead, to their almost certain death.
Sound can confuse animals, too. Military sonar has been found to disorientate migrating whales, leading them to become repeatedly beached. In fact, there is also evidence that anthropogenic sounds have changed the way whales and birds communicate, forcing them to demonstrate the so-called Lombard vocal response, where they effectively have to raise their voices to be heard over the noise, which of course only worsens the problem. In humans this can lead to higher levels of aggression and increased blood pressure, and by extension the encouragement of a shouting society: if you don't make a big noise you won't be heard.
"There's a clear distinction between sound and noise," says Philip Evans, an occupational health consultant with RPS Group who has more than 25 years' experience specialising in acoustics and vibration. "Noise is sound you don't want to hear", he says. And in terms of its impact on most humans, the vast majority of this comes from transportation: cars, trucks and planes in particular.
The definition of light pollution, on the other hand, is less straightforward. There is no consensus, says Christopher Kyba, a physicist with the Institute of Space Sciences at the Free University of Berlin, who has been researching the subject. "Some people say that all human light is pollution, while others believe it only begins at certain thresholds", he says. Part of the problem is that lighting is often associated with safety, so one person's light pollution could be another's (real or imagined) security.
In occupational health, the link between exposure to noise and direct damage to the auditory system is well established, but for less direct health effects the evidence is less clear, says Evans. Even so, the WHO warns of the effects that noise can have in provoking disturbed sleep, including raised blood pressure and cardiac arrhythmias. And noise seems to affect cognitive performance too. Studies have shown that children in schools around airports tend to under-perform, while children from noisier areas in general have increased stress hormone levels and elevated resting blood pressure.
With light pollution the evidence is even more damning, says Kyba. Normally when the sun goes down, our bodies are wired to start producing the hormone melatonin. But for most of us this is generally suppressed because of artificial lighting. "Melatonin is a powerful antioxidant," he says. So besides helping to explain why some people find it so difficult to get to sleep, its suppression should also carry an increased risk of cancer - and indeed it does, says Kyba. "Shift workers tend to have higher incidences of breast and prostate cancer." It's even been shown that breast cancer rates are higher in places with higher lighting levels, he adds. Even dim light at the wrong time - the soft glow of an LED clock or standby display of a DVD player in the bedroom - can have a negative impact on people, Kyba claims.
The disruption of our circadian rhythms also has a knock-on effect on how we metabolise food. In animal studies it has been shown that eating food at different times can alter the rate at which it's metabolised, resulting in an increase in weight. There is now a growing body of evidence to suggest that this is also happening in humans, to the extent that it is contributing to obesity levels, says Kyba.
Hardly surprising, then, that the American Medical Association announced earlier this summer a new policy recognising the need to understand the risks posed by excessive light at night and its disruption to sleep.
So what can we do about these menacing problems? While it's easy enough to unplug devices in the bedroom - though often not very practical - it's harder to block out the glow of the city and the sound of traffic filtering in through our windows. To get a sense of the scale of the challenge, stop, look and listen during WWF's Earth Hour, an annual campaign held in March which encourages people and businesses to switch off for an hour.
Campaigners for action on both sound and light pollution can point to the fact that, in general, things that are bright and noisy consume more energy and produce more carbon emissions than their dimmer, quieter equivalents. In some cases, they also cost more, too. According to the Carbon Trust, UK businesses and public sector organisations could each year save £350 million and the equivalent of 2.2 million tonnes of CO2 just by switching off unnecessary lighting.
So it's no surprise that tackling these pollutants is rising up the political agenda. But as it does so, there are some awkward tradeoffs emerging. Take the recent fashion for architectural lighting. It can bring the nightscape of a city like London into elegant relief - but it also adds to skyglow. Then there's street and security lighting, the spread of which has been driven by concern over personal safety. It certainly helps make people feel secure (although the actual impact on crime levels is much less certain), but it also saturates the night sky - in part thanks to badly designed lamps, which waste much of their energy sending light upwards.
Poor design can make things worse. Street lamps should illuminate a road to make it safer for drivers and pedestrians, but if done poorly, such as having lights that shine out in all directions as is often the case, then it can actually increase glare, making the road less safe and more confusing.
In fact, shining light just above the horizontal is more of a problem than pointing it directly up into the sky, says Kyba. Straight up there's a good chance that most of that light will escape the atmosphere. But horizontally it has further to travel, where eventually it becomes scattered and reflected back down to earth, contributing to that familiar nightglow that hovers over urban landscapes.
This can be avoided with so-called 'full cut-off lights', which ensure that none of the light is emitted above the level of the horizon, directing it downwards only. This becomes obvious when you drive along a road lit by these kinds of lights, says Kyba. The light is so efficiently directed downwards that it cuts glare to the point that it appears as if the lamps ahead are turned off and only switch on as you approach them. This is now being used in cities and on streets around the world, although it remains very much a minority practice.
Combining this approach with other new technologies can yield huge benefits, as was demonstrated recently by a group of researchers led by Chintan Shah at the Delft University of Technology in the Netherlands. They experimented with using motion sensors, wireless communications and dimmable streetlights to ensure that lighting levels remained very low unless there was activity in the area. The results suggested this could cut the Netherlands' €300 million annual streetlighting electricity bill, and the 1.6 million tonnes of CO2 associated with it, by as much as 80%.
In the UK - where lighting accounts for one fifth of all electricity consumed - the use of smart sensors could equally help to mitigate against that other contributor to skyglow and light pollution: the office block. While some companies have started to do this, far too many leave their lights on throughout the night, says John Meacham, of the British Astronomical Association's Campaign for Dark Skies. They say that they need them on constantly for cleaners and for security, but that argument simply doesn't stand up to scrutiny, he says.
Indeed, there's growing evidence that bright lights in general do not in themselves make places safer - even if there's a widespread belief that they do. "Recent energy saving late night switch-offs of street lighting in Essex, Buckinghamshire, West Sussex and other areas were not followed by increases in crime rates, says Meacham. On the contrary, "there was a substantial fall in crime rates". The UK government's report on Home Security and Crime Reduction advice now states that harsh glaring lights are not a deterrent to criminals.
Perhaps surprisingly, offices can also be a significant source of sound pollution. It used to be the case that any new installation of an external heating, ventilation or air-conditioning unit to a building was required to be no louder than the background levels in the area, says Evans. However this led to an effect similar to whales having to sing louder to be heard. "Each new installation raises the baseline, so you get 'creeping background'", he says. Now, regulations require new installations to be set at 10 decibels below the existing background, so there won't be any net increase, says Evans.
But what about the biggest source of sound pollution: transportation? It has been suggested that as we move away from combustion engines towards electric vehicles, so sound pollution will drop significantly. In fact EVs are so quiet that some manufacturers are looking at introducing artificial sounds so people can hear them coming. There has even been a proposal to mount a speaker in the front of one model, emitting 'conventional' engine noise.
But Evans is not convinced that EVs will have much impact on reducing noise pollution, even without these artificial sounds. Even if you replaced half of all cars with EVs, this would only reduce ambient levels by around 3dB, he says. And this is only taking engine noise into account. "At higher speeds a lot of the noise comes from the tyres," he says. There are some porous road surfaces that help to reduce the sound of traffic, but these need regular maintenance to keep them free of dirt.
Noise remains the Cinderella of pollutants, attracting little attention. But there are some whispers of activity under way. At the European level, the Environmental Noise Directive requires all member states to map noise levels. And in the UK the Department for Environment, Food and Rural Affairs [Defra] is attempting to create Quiet Areas, a concept not that dissimilar to Dark Sky Parks, but for noise. It is currently working on new standards for noise safety thresholds. However, Defra has yet to come up with any hard values and the noise maps of Europe only cover main roads, says Evans.
Aviation is also being muffled - to some extent. As tougher regulations come into force on noise produced during take-off and landing, older planes will eventually be replaced by a new generation of jet engines which, unlike their predecessors, are capable of controlling the amount of air that bypasses the main jet turbine - one of the chief causes of high noise levels. The US military and a handful of private engineering firms are even working on ways to enable aircraft to travel at supersonic speeds, but without the sonic boom that so dogged the Concorde throughout its lifespan. Flight tests have shown that it is possible to shape the nose of planes so that they cause any shockwaves produced - which are the cause of sonic booms - to travel upwards only. In the long term we might even see some aeroplane flights replaced by airships: an almost infinitely quieter alternative.
Meanwhile, though, with aviation the fastest growing form of transportation, it is questionable whether these technologies will result in any net reduction of noise pollution. Indeed, as with any mitigation strategy, there is always the risk of making things worse thanks to the rebound effect. Making aircraft quieter and more fuel efficient could easily lead to more flights and so more noise. And making lights cheaper to run could remove the incentive to turn them off, adds Kyba.
But that's no reason to despair. As energy costs rise, evidence of health impacts grows, and concerns over safety shift from fear of the dark to fear of climate chaos, the tide could turn.
In time, with the mass deployment of new technologies such as EVs, adaptive jet engines, noise-absorbing road surfaces and smart lighting, we might be able to not just slow the increase in the amount of light and sound pollution, but actually reduce it to create a quieter and darker world.
Perhaps then we could all live as peacefully as the residents of Galloway.
Duncan Graham-Rowe is a science and technology journalist based in Sussex.