We work by day and sleep at night; except when we don't or can't. And right now, about 30 per cent of Canadians work well into the night when many of them would rather be asleep. They are nurses, emergency room doctors, oil-rig workers, miners, autoworkers, office cleaners, police officers, prison guards, factory workers, salespeople and service personnel. They all face rotating shift work – and the problems that this causes.

One of these problems is called “light pollution,” and it is caused by exposure to a proliferation of artificial night light.

A growing concern
There is mounting evidence that such pollution not only affects human health but also the health of the entire planet.

Night workers are exposed to light when their bodies expect darkness. This causes changes to their circadian rhythm, which governs the natural rise and fall in body temperature, respiratory rate, urinary excretion, cell division and hormone production.

A circadian rhythm that is out of sync can lead to things such as chronic fatigue or jet lag. Other health effects include an incidence of peptic ulcer disease, which is eight times that of the general population, and increased cardiovascular mortality. These are documented in a policy paper developed by Dr. Harold Thomas, chair of the wellness section of the American College of Emergency Physicians.

Other research points to an increased risk of breast cancer, a risk that grows the longer a woman works at night. Why there's an increased risk is open to research, but many in the field theorize that it's the artificial light at night that is to blame.
 

Page 1 of 5 - Learn about night light's impact on your health on page 2.
Health hazards for women working late nights
Julia Knight, an epidemiologist and researcher at the Samuel Lunenfeld Research Institute at Mount Sinai Hospital in Toronto, is one expert pointing a finger at artificial light.

"Quite a few studies show that women who work rotating night shifts over a period of years are at an increased risk of breast cancer," she says. "One of the theories is that their exposure to bright, artificial light at night suppresses their melatonin."

Melatonin has been shown in both cell-culture studies and animal studies to be an anti-cancer hormone. During the day, levels are significantly lower, as they are in women who work nights. The only time melatonin levels rise is at night in the dark.

The link between low levels of melatonin and breast cancer is also supported by a study developed by Itai Kloog, a researcher in the department of natural resources and environmental management at the University of Haifa in Israel.

According to his research, the more lit up a settlement is at night, the higher the rates of breast cancer. Kloog explains that exposure to artificial lighting reduces the amount of melatonin the body produces, and this puts women at greater risk of developing breast cancer.

Melatonin stops growth of cancer
One of the more convincing studies of the influence of melatonin on cancerous tumours involved implanting human breast cancer under the skin of female rats. The researchers then took blood samples from several healthy, premenopausal volunteers.

The samples were collected under three different conditions: during the day; at night following two hours of complete darkness; and at night following 90 minutes of exposure to bright fluorescent light.

The blood samples were pumped directly through the developing tumours. The blood collected from the subjects in total darkness drastically slowed the growth of the tumours.

In contrast, the blood collected from the light-exposed subjects stimulated tumour growth. The researchers concluded that the results were due to the direct effect of the melatonin on the cancer cells.


Page 2 of 5 - Find out more about melatonin's effects on the body on page 3.

Preventive measures
However, the health of people who work at night need not be totally compromised. Research by Dr. Robert Casper, also at the Samuel Lunenfeld Research Institute, points to a possible solution: night goggles.

Casper collected salivary samples on three different nights from awake student volunteers. Samples from students kept in darkness showed that melatonin levels steadily rose to peak at about 2 a.m. – similar to what happens when we sleep. Samples from the same students subjected to bright light showed no melatonin rise. For the third night, the students wore goggles that filtered out the blue and green end of the light spectrum, but let through the red and yellow light.

They experienced the same rise in melatonin as they had in the dark, although they were in a brightly lit room, and were able to see and function well on simulated driving tests. This proved that it is only the blue and green band of the light spectrum that suppresses the body's production of melatonin.

"Now we're trying to find the narrowest band of light to block so that the goggles are not so yellow looking," says Casper. "Even so, the goggles let through more than 70 per cent of the available night light, which is more than enough for people to go about their business."

So guarding the long-term health of night-shift workers may be as simple as donning a pair of cool, comfortable specs.

Lights out to save the birds
It's not just humans who appear to be affected by the brightly lit night sky. The first compelling evidence that artificial night lighting affected life on earth came from studies of birds.

"For unknown reasons birds are attracted to any tall, brightly lit structure, like a moth to a flame," says Michael Mesure, the executive director at Fatal Light Awareness Program (FLAP) in Toronto. "They get drawn into large urban centres and either collide outright with the structures, or they circle in the light attempting to escape until they drop from exhaustion."

The estimated number of birds that die annually across North America because of these strikes ranges from 10 million to 100 million.


Page 3 of 5 - Learn how light pollution extends beyond cities on page 4.

Artificial light not just in urban areas anymore
Even in remote areas, light pollution is exacting its deadly toll.

"For the first time in history, light from our industrial activities extends to the waters of the Grand Banks," southeast of Newfoundland, says Bill Montevecchi, a professor of marine ornithology at the Memorial University of Newfoundland in Saint John's.

"There are all these off-shore oil platforms lit up like huge birthday cakes," says Montevecchi. "Lighthouses have always attracted nocturnal birds, and now we have this new fatal attraction."

In a chapter of the book Ecological Consequences of Artificial Night Lighting (Island, 2006), Montevecchi details the profound effects of night light on birds that live far offshore. Other chapters in the book cover mammals, reptiles, fish, insects, land birds and plants.

"We can save some of these creatures by minimizing our impact without compromising other things such as safety. Because whenever there is better or stronger environmental protection, there is better protection for humans," says Montevecchi.

Light pollution extinguishing stars
Tom Bolton, a professor of astronomy and astrophysics at the University of Toronto, agrees. But he's also worried about the loss of an entire field of research. Over the years, he has seen the stars go out one by one.

Light pollution from Richmond Hill, Ont., just north of Toronto, has changed the type of science he can do at the city's David Dunlap Observatory.

"We can no longer do much imaging," says Bolton. "Sky brightness has increased by a factor of somewhere between 40 and 100 per cent. This means you can no longer even see the Milky Way, except on the rarest of clear, moonless nights – and then only straight overhead. I have a photo mosaic of a cluster of stars observed between 1935 and 1970. You can see the stars becoming more and more obscured. By 1970 you can hardly see the stars against the sky background."

Light pollution is the culprit killing the beauty of the night sky.

Badly designed lighting fixtures emit light upward into the sky, where it gets scattered by atmospheric dust and water molecules. This produces a kind of haze that reduces the contrast between starlight and the sky.

"We've lost the experience of the night sky," says Bolton. "People don't look up any more because there is nothing to see."


Page 4 of 5 - Find out how Canada is fighting light pollution on page 5.

This loss, coupled with the mounting evidence pointing to the real health concerns linked to artificial light, has triggered some jurisdictions to address the issue of light pollution.

Already nine American states have adopted legislation designed to limit light pollution. Some regional authorities in Europe have passed similar laws. And the Czech Republic has enacted legislation to tackle light pollution.

Energy conservation, improved traffic safety through glare reduction and a real desire for a better view of the night sky are among the rationales for enacting such measures.

Canada cuts back on light pollution
And changes are happening right here at home. Since 1994, as a result of Bolton's work, Richmond Hill has had a light pollution control bylaw. It inspired a similar bylaw in Markham, Ont.

"It has made a huge difference," says Bolton. "Sky brightness was increasing at a rate of 30 per cent a year. Now it's at less than 10 per cent a year."

Calgary, too, is doing its bit to reduce the light it throws into the sky. It has embarked on an ambitious program of retrofitting more than 40,000 wasteful, residential streetlights with fully shielded, low-glare fixtures that direct their light downward onto the street where it is needed.

These more efficient lower-wattage lamps will save taxpayers $2 million in electricity costs a year; they will also make the streets safer for both drivers and pedestrians.

And Toronto recently became the first city in the world to approve a migratory bird protection policy. As part of this move, the city, along with 15 partners including FLAP, downtown landlords and Toronto Hydro Corporation, have announced their Lights Out Toronto! initiative in an effort to get the message out to the public that light pollution is an issue that concerns us all and one that everyone can do something about.

So while turning off the lights at night is sure to be good for the birds, it is also something that just might bring you and your family health benefits and return dollars to your pockets. Who can argue with that?


Page 5 of 5 - What is light pollution? Learn about artificial light and its effects on page 1.