Findings About Air Pollution and Heart Disease / Fossils from the 'Missing Years' in Africa / U.S. Bans Ephedra for Weight Loss
This is SCIENCE IN THE NEWS, in VOA Special English. I'm Bob Doughty. And I'm Sarah Long. This week -- fossils help bring light to a mysterious time in prehistoric Africa.
New findings about air pollution: Could it be worse for the heart than the lungs?
And, in the United States, the government acts to ban a weight-loss product.
Researchers say they have identified animal fossils from twenty-seven-million years ago in what is now Ethiopia. The remains are from the middle of a time called the "missing years" or the "dark period." This is because scientists have so little information about the mammals that lived then.
The period began thirty-two-million years ago. Africa and Arabia were a single continent, a huge island known as Afro-Arabia. The period ended twenty-four-million years ago, after a land bridge formed with Eurasia.
John Kappelman is an anthropologist at the University of Texas in Austin and leader of the American and Ethiopian search team. Mr. Kappelman says eight million years is a long time to lack information about a continent. He says scientists have only been able to guess what happened to African mammals during that period.
The remains found in the Chilga area of Ethiopia offer important evidence.
The remains include teeth, skull pieces and other bones. The scientists found them in a farming area about two-thousand meters above sea level, in the highlands of Ethiopia. Satellite pictures helped the researchers decide where to dig. The fossils came from about seventy different digs. The magazine Nature published the findings.
The scientists say the fossils come from before large numbers of animals began to arrive in Africa from Europe and Asia. The fossils also show that some animals existed millions of years before scientists had thought.
The researchers found several kinds of ancient proboscideans. These are animals with trunks. Modern elephants are proboscideans. Scientists have long thought elephants began in Africa. They say this discovery proves that theory. The ancestors weighed about one-thousand kilograms, a lot smaller than African elephants today.
John Kappelman says the elephant ancestors were one of the few African mammals that survived the invasion of mammals from Eurasia. He says elephants got their start in Africa during the eight-million-year period, and then spread around the world.
The researchers also found the remains of an ancient animal with two horns on its head, called the arsinoithere. The scientists were excited, because this is the youngest set of such remains yet discovered. The animal is much larger than its ancestors. Earlier forms were about the size of pigs. But the arsinoithere found at Chilga was about two meters tall and weighed more than two tons.
They were similar to the modern rhinoceros. The two are not related. In fact, scientists thought arsinoitheres had disappeared from the Afro-Arabian continent once rhinos arrived from Eurasia. One researcher says it now appears they did not compete for survival.
Scientists say they expect more discoveries to come about the mammals that lived during the so-called missing years.
A study finds that air pollution is worse for the heart than the lungs.The American Heart Association published the findings in its magazine, Circulation.
Researchers used information given by more than half-a-million adults between nineteen-eighty-two and nineteen-ninety-eight. The information is from a continuing study by the American Cancer Society on cancer prevention. The study included people thirty and older living in cities where officials kept records on air pollution.
During the sixteen-year period, one in five of the people in the study died. The scientists found that heart disease caused about forty-five percent of the deaths. Only eight percent of the people died from diseases of the breathing system.
The researchers compared the information with air pollution records from more than one-hundred-fifty cities. The scientists controlled for things that increase the risk of heart disease, like smoking and being overweight. Still, they found a stronger link between air pollution and heart disease than respiratory disease.
Arden Pope of Brigham Young University in Provo, Utah, led the study. He says air pollution is not the main cause of heart disease. But, he says, breathing polluted air causes swelling and worsens disease in the arteries of the blood system. He says this affects the ability of the heart to operate effectively. The study also suggests that air pollution harms the nervous system, leading to abnormal heartbeat.
The study involved air polluted by small particles of soot. Vehicles that use diesel fuel create a lot of soot. So do some factories. But it is also released into the air by burning wood and other substances including animal waste and vegetable oil for fuel.
Soot was cause for a different concern in another recent study. Scientists with the American space agency, NASA, suggest it as a major cause of global warming. The NASA researchers say soot may be responsible for twenty-five percent of global warming observed over the past century.
With computers they recreated the effects of industrial gases and other influences on world climate. They say carbon dioxide and other gases that trap heat have been the main cause of recent global warming, and will remain so. Still, they say soot may be worse than has been thought.
The study says the problem is how soot interacts with snow and ice.
Snow and ice have highly reflective surfaces. A lot of the sunlight that hits them is forced back up toward the sky. This helps prevent melting. But the scientists say the problem develops when snowflakes pick up fine particles of soot as they fall. The black carbon in soot reduces the ability of snow and ice to reflect sunlight. Instead, the black soot absorbs the energy and warmth, and causes melting.
James Hansen and Larissa Nazarenko of the Goddard Institute for Space Studies reported the findings. They estimate that soot particles in snow reduced reflectivity by three percent in northern land areas of the world. Their estimate for the Arctic is one-and-a-half percent.
The scientists say the soot causes the melting season of glaciers to begin earlier and last longer. This has a large effect, they say, because wet snow is much darker than dry snow. So the problem increases.
The scientists estimate that soot is two times as effective as carbon dioxide in changing surface air temperatures. But they say the good news is that cleaner diesel engines and other technologies are being developed to reduce soot.
The study is in the Proceedings of the National Academy of Sciences.
In the United States, the government is acting to ban the sale of ephedra as a product to help people lose weight. Ephedra is a plant that contains ephedrine and pseudoephedrine. These substances can increase a person's energy level and cause weight loss. However, officials warn that ephedra also raises blood pressure. Ephedra has been linked to heart attacks, strokes, seizures and deaths.
The secretary of Health and Human Services announced the ban. Tommy Thompson urged people to stop using ephedra even before the ban takes effect. He said he did not want to delay the announcement, because people often try to lose weight at the start of a new year.
The market has grown sharply for herbal products known as dietary supplements. Companies do not have to prove them safe and effective the way drug makers do. In nineteen-ninety-four, Congress limited the ability of the Food and Drug Administration to take action against supplements. This is the first ban since then.
The ban will not include the version of ephedra used in medicines to treat breathing infections. Ephedra has long been used for this purpose as a traditional medicine in China, where the plant is called ma huang.
SCIENCE IN THE NEWS was written by Caty Weaver and produced by Cynthia Kirk. I'm Sarah Long.
And, I'm Bob Doughty. Join us again next week for another program about science in Special English on the Voice of America.