LIFE in big cities means pollution of all kinds - typically air, water and noise - but few people know that the bright city lights in many forms are also pollution that can be dangerous. Zhang Qian sees the light.

Though we seldom give it much thought, we are constantly subjected to light pollution in big cities - from light bouncing off glass-walled buildings to flickering fluorescent office lights to strobes at night clubs.

Long exposure may cause damage to sight, skin and the nervous system. But adjustments in interior decoration and habits can reduce exposure.

The idea of light pollution was first raised in the 1930s to describe the negative influence of urban lighting to celestial observation, according to Professor Huang Jiping with the Physics Department of Fudan University.

Since then the idea of light pollution has been expanded to cover many ways that bright light has a negative impact on people and the environment. Light can be ultraviolet (we know that's bad for skin and eyes), infrared and visible.

"There are generally three kinds of light pollution in daily life - white-brightness pollution, artificial lighting and color light pollution," says Professor Huang. "All are common in urban areas, especially big cities like Shanghai."

Dr Zhou Min, chief of the eye department at Fudan University's Eye and Ear Hospital, agrees about the potential accumulated damage over time, but he hasn't seen specific cases.

The white-brightness pollution comes from many buildings with glass walls, glazed panels, polished metal and marble and stone that reflect dazzling sunlight which can hurt the eyes. Most people shield their eyes because the light is uncomfortable.

Long exposure to this kind of dazzling environment can damage the retina and iris; there's a higher occurrence of cataracts among these people, says Dr Zhou.

Long exposure to this kind of blinding light can cause dizziness and distraction.

Glaring interiors with bright fluorescent lighting, highly polished metal and marble can create similar discomfort.

When the sun sets in nature, the world gets dark. But street lights, advertising lights, neon and other bright and pulsing lights turn night into day. This kind of glare over time is also bad for vision; it can disrupt sleep and the normal biological clock.

Night clubbers are exposed to different pollution from colored, flickering and pulsating lights - black lights, strobe lights, fluorescent lights and lights that bounce off hundreds of mirrored facets of decorative balls hung above a dance floor.

Again (not to scare the party animals who know this) prolonged exposure may cause discomfort and disorientation. Some people get dizzy, feel sick to the stomach and experience insomnia. Add alcohol to the mix and there can be some unpleasant sensations.

"The ultraviolet radiation in black light is even stronger than that in natural sunlight," says Professor Huang. In the most extreme cases, he says, long exposure may lead to nose bleeds, cataracts, loss of teeth, leukemia or other cancers. But nobody's going to stay on the dance floor that long.

It's well known that long exposure to ultraviolet radiation can cause skin cancer; it accelerates the aging of skin cells and causes wrinkles and discoloration.

Precautions are obvious: limit exposure, wear a hat and proper clothing, wear sun screen, wear polarized lenses, and so on.

We can do something about interior light pollution. Use satin or matte finish for tiles and surfaces; use off-white or cream-colored paint, don't overdo the mirror and glass surfaces, or make sure they don't get a lot of light; use heavy curtains or blinds, and avoid fluorescent lighting.

Fluorescent light is high in ultraviolet radiation. Incandescent lamp and energy-saving light bulbs of 60-100w - not harsh - are recommended. Hanging lamps that sway are not good for the vision.

Stay away from too much black light , flickering light and strobes.

Heart bypass queried

Two new studies could change care for hundreds of thousands of heart patients each year. One finds that bypass surgery has been overrated for many people with very weak hearts from clogged arteries and previous heart attacks. The other challenges the way artery-opening procedures have been done for decades.

It was the first big test of doing balloon angioplasty to clear heart arteries through an arm instead of a leg. Complications were fewer with the arm method and at hospitals that did this more often, deaths, heart attacks and other big problems were lower, too.

The arm method is common in India, Israel, Europe and Canada, but less than 5 percent of US cases are done this way.

"This is the way we should head," and more doctors should be trained, said Dr Edward McNulty of the University of California, San Francisco. He is a leader of the American College of Cardiology conference where the studies were released last week.

The bypass study's surprising result is "a blockbuster," McNulty said. The operation did not improve survival for heart failure patients who already were taking medicines to control high cholesterol and high blood pressure.

Estrogen relief

Strokes and other health problems linked with estrogen pills appear to fade when women quit taking them after menopause, according to the first long-term follow-up of a landmark study.

It's reassuring news for women who take the hormone in their 50s when menopause usually begins.

The study bolsters previous evidence that concerns about breast cancer and heart attacks are largely unfounded for those who take the hormone for a short time to relieve menopause symptoms. Estrogen-only pills are recommended just for women who have had a hysterectomy, and the study focused only on them.

About 25 percent of women in menopause have had hysterectomies. Other women are prescribed a combination of estrogen and progestin because for them, estrogen alone can raise risk of uterine cancer.

Prostate cancer screening

The longest study on prostate cancer testing provides more evidence that screening doesn't cut the chances of dying from the disease. In a 20-year study of over 9,000 Swedish men, researchers found no difference in the rate of cancer deaths between the men periodically screened and others.

Routine screening for prostate cancer is controversial and the new results aren't likely to end the debate about the value of testing.

Critics say screening leads to unnecessary biopsies and treatment with little proof that it saves lives. Testing is done with a physical exam and a PSA blood test.

Breast cancer

Smoking raises the risk of breast cancer for healthy-weight and overweight women but not for those who are obese, new research suggests.The reason is not known and more research is required. It could be that they die sooner from other causes.

It's a first-of-its-kind finding, and even if other studies confirm it, it doesn't mean that smoking is safe for women who weigh way too much, researchers say.

"Smoking is a strong risk factor for many diseases other than breast cancer," including lung cancer and heart disease, said Juhua Luo, a West Virginia University scientist who led the study and presented results Sunday.

Obesity has long been recognized as a risk factor for breast cancer, but research tying smoking to breast cancer is much weaker. Luo's study found a 16-percent higher risk of breast cancer among postmenopausal women who smoke or used to smoke versus those who never did.

Those who were healthy-weight or overweight, with BMIs under 30, were more likely to develop breast cancer if they smoked, 16-25 percent. But searchers saw no added cancer risk in obese smokers (BMI of 30 or above).