Science News Digest

This is Sarah Long. And this is Bob Doughty with SCIENCE IN THE NEWS, a VOA Special English program about recent developments in science. Today, we tell about the raising of the sunken Russian nuclear submarine Kursk. We also tell about the increased risk of breast cancer for women who work at night.

Dutch recovery experts have raised the sunken Russian nuclear submarine Kursk. The recovery ends fears of serious environmental threats from the submarine. The Kursk had been on the bottom of the Barents Sea for more than a year. The submarine was on training exercises when it sank in August of last year. Scientists feared that its two nuclear reactors were leaking radiation. Earlier this month, recovery experts from two Dutch companies lifted the Kursk about one-hundred-meters. They raised it to a level near the water surface. Scientists reported normal radiation levels in the area.

The Kursk was one of Russia's most modern submarines. Two explosions caused the Kursk to sink. The cause of the explosions still is not known. One-hundred-eighteen crew members on the submarine died. Some naval experts believed removing the Kursk from the bottom of the sea would be impossible. The submarine weighs more than eighteen-thousand tons. Scientists said it would be difficult to lift the ship out of the mud at the bottom of the sea. However, workers raised the submarine in about fifteen hours. The job cost Russia a reported sixty-five-million dollars.

The Dutch recovery experts started developing plans for the operation in May. It took more than three months of work at sea to complete. Recovery experts had expected to raise the Kursk last month. However, storms and technical problems caused repeated delays. Russian officials and recovery workers worried about the postponements. They said severe weather conditions would have made it too dangerous to raise the submarine. The Barents Sea is in the Arctic area.

In July, divers cut twenty-six holes in the submarine. Devices that shoot water at high pressure helped make the holes. The goal was to create spaces to attach strong steel ropes called cables to lift the submarine. Each cable contained fifty-four ropes of steel. The workers added equipment to hold the cables. Then they connected the submarine to the cables.

Late last month, a huge ship called Giant Four arrived near the Kursk. This barge had sailed from the port of Kirkenes, Norway. It brought equipment to cut off the front part of the submarine. This front area contains underwater missiles called torpedos.

Recovery workers had feared that a torpedo might explode while they cut the rest of the submarine free. They also had worried that the front part of the submarine might break off. That would have wrecked the lifting operation. However, the workers successfully cut off the front part of the submarine.

Russian weather experts continually reported air and sea conditions to the recovery team. Calm periods often lasted only five or six hours. Divers worked underwater eight hours at a time to prepare the submarine for lifting. Underwater cameras recorded their progress and the position of the submarine. Devices to measure radiation provided information about the condition of the nuclear reactors. They showed no signs that the reactors were leaking radiation.

For several weeks, bad weather delayed the recovery operation. Finally, the team attempted to raise the Kursk on October Eighth.

Workers on the Giant Four barge operated the cables lifting the submarine. The recovery team controlled the pressure on each cable with special devices. Computers measured the force on the cables as the submarine rose. Centimeter by centimeter, the submarine was lifted to a place just below the surface of the water. Workers connected the Kursk to the bottom of the barge. Another large ship pulled the barge and submarine slowly to port near Murmansk, Russia.

Large floating devices called pontoons brought the Kursk up to the surface of the water. Workers removed the devices that held the cables. This action freed the submarine from under the barge. Then the Giant Four barge began sailing back to Kirkenes, Norway. It had successfully brought the Kursk home from the bottom of the sea.

The Russian Navy now is working on the wrecked submarine. Officials will remove the remains of the crewmen who died on the Kursk. The bodies will be given to the families for burial.

Workers also will remove more than twenty missiles from the submarine. Scientists will examine the inside of the Kursk. They will try to find the cause of the explosions that sank the submarine. However, many experts say this evidence is probably in the front part of the submarine. That part of the Kursk remains on the bottom of the Barents Sea. Plans call for trying to raise it next summer.

You are listening to the Special English program SCIENCE IN THE NEWS on VOA. This is Bob Doughty with Sarah Long in Washington.

The Journal of the National Cancer Institute has published two new studies about breast cancer and women who work at night. These studies suggest that women who work nights have a greater chance of getting the disease than other women. The research suggests that bright light during the night may decrease production of a brain chemical called melatonin. An organ called the pineal gland makes melatonin during the night.

Reduced levels of melatonin may cause levels of the hormone estrogen to increase. Earlier research has linked increased estrogen levels with breast cancer.

The women in the studies worked between seven at night and nine in the morning. The body produces the most melatonin after midnight, between one and two in the morning.

Researchers from the Fred Hutchinson Cancer Research Center in Seattle, Washington carried out one of the studies. Scott Davis led a team that examined the records of more than one-thousand-five-hundred women. They were from twenty to seventy-four years old. About half the women had breast cancer. The others did not have the disease.

The researchers found that the women who worked nights for up to three years were more likely to have breast cancer than the other women. These night workers showed about a forty percent higher chance of developing the disease. Women who had worked nights for more than three years were sixty percent more likely to get the disease.

Night workers were not the only women showing increased risk from bright lights during the night. Other women who were awake during early mornings also showed similar risks. Women who stayed up past two in the morning at least three times a week had a forty percent higher risk. However, women who slept with some light in their bedrooms did not show a higher risk for breast cancer. Also, turning on lights for short periods during the night did not affect a woman's chance of developing the disease.

Researchers at Brigham and Women's Hospital in Boston, Massachusetts reported another study. Their research included more than seventy-eight-thousand nurses. The nurses are part of a continuing Nurses' Health Study. The scientists examined the medical and work records of these women between Nineteen-Eighty-Eight and Nineteen-Ninety-Eight. One group of nurses worked at least three nights each month.

They did this for as many as twenty-nine years. These women were about eight percent more likely to develop breast cancer. However, nurses who worked at least three nights each month for more than thirty years were thirty-six percent more likely to get the disease.

Earlier research also has suggested that working at night is unhealthy. Night work has been blamed for increased risk of several conditions. They include heart disease and problems involving pregnancy and the stomach and intestines. Working some days and some nights also is suspected of causing these problems.

This Science in the News program was written by Jerilyn Watson. This is Bob Doughty. And this is Sarah Long. Join us again next week for more news about science in Special English on the Voice of America.