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 new limits on arsenic in drinking water. We tell about how sea turtles are able to swim across the ocean and back. And we tell about the world's smallest electronic transistor.
The Bush Administration has decided to change its policy about limits of a harmful element in drinking water. The goal is to reduce levels of the poisonous element arsenic. Most arsenic is found naturally in water. Arsenic also is found in rocks, soil, air, plants and animals. It also is produced as a waste product in some industries.
Several months ago, the Bush administration suspended a rule approved by former President Clinton to reduce acceptable levels of arsenic in drinking water. Now the administration has decided to accept the proposed level.
Christine Whitman is the head of the Environmental Protection Agency. She said the agency will now permit ten parts of arsenic for every thousand-million parts of drinking water. Water systems across the country must obey the new limit by Two-Thousand-Six.
The new limit greatly reduces the current acceptable level of arsenic. The present level is fifty parts of arsenic for every thousand-million parts of water. This level was established more than fifty years ago. Mizz Whitman said the decision will improve the safety of drinking water for millions of Americans. And she said it will protect against the risk of cancer, heart disease and diabetes.
Former President Clinton had approved the new level in January only a few days before he left office. But the Bush Administration suspended the action in March. It said the new limit would be too costly. And it questioned the scientific reasons for it. Health and environmental activists criticized the move.
Some environmentalists say that the new level of ten parts of arsenic for every thousand-million parts of water is still too high. These activists say only three parts arsenic should be permitted. They say studies made since President Clinton left office prove this.
A recent National Academy of Sciences report says arsenic is more dangerous than scientists had earlier believed. The academy says even a very small amount of arsenic could increase cancer risks. It says the new level would result in a cancer risk much higher than what the E-P-A considers acceptable. Arsenic has been linked to a number of cancers. They include cancer of the lungs, bladder, kidneys and liver.
However, some water system officials, mining industry officials and others oppose the new limits. The American Waterworks Association represents most water treatment centers in the nation. It says current techniques to remove arsenic from water are very costly. The organization says the new arsenic limits could cost the nation about five-thousand-million dollars.
The National Rural Water Association represents more than twenty-thousand small communities. It also criticized the decision. It says the new limits could cost families as much as five-hundred dollars a year.
The Environmental Protection Agency says it plans to help water systems in small communities. It will spend twenty-million dollars during the next two years to develop new technologies to meet the new limits.
You are listening to the Special English program SCIENCE IN THE NEWS on VOA. This is Sarah Long with Bob Doughty in Washington.
American scientists have found strong evidence that baby sea turtles are born with the ability to recognize and measure Earth's magnetic fields. They found that the sea turtles use the magnetic fields to guide them as they swim great distances across the ocean.
Scientists at the University of North Carolina at Chapel Hill did the research. Science magazine reported the findings.
The scientists say the baby sea turtle is one of the great wonders of the animal world. Baby turtles swim directly to the open sea shortly after breaking out of their eggs. The young turtles follow complex paths that often lead across large areas of seemingly endless ocean. Baby sea turtles swim across the Atlantic Ocean and back all by themselves. People have wondered for years how they do this.
The longest and most surprising trips are made by young loggerhead turtles. Young loggerheads in the North Atlantic Ocean swim more than fifteen-thousand kilometers across the ocean before returning to the North American coast.
Loggerheads in the state of Florida follow a huge, circular current of warm water known as the North Atlantic gyre. The gyre moves from the East Coast of the United States across the North Atlantic and then south along the coasts of Spain and Africa before turning west to complete the circle. Water in the gyre is generally warm and food there is plentiful. Turtles that leave the gyre often die from the cold water.
The scientists wanted to find out if baby loggerhead turtles could recognize the magnetic fields in different parts of the North Atlantic gyre. They used turtles that had never been at sea before. They placed the turtles in a container filled with saltwater. They put wires around the container. The wires produced magnetic fields similar to those found in different parts of the gyre. Whenever the turtles were in a magnetic field like that found in the ocean, they swam in a direction that would keep them in the warm current.
One of the scientists, Kenneth Lohmann, says the findings provide direct evidence that turtles can use Earth's magnetic fields as markers. He says similar systems might exist in other ocean creatures and even some birds.
Scientists report they have created the smallest device to carry electrical current ever made. The device is called a transistor. It is about one-million times smaller than a grain of sand.
Transistors are used in many electronic devices to control the flow of electrical current. True transistors can turn the flow of electricity on and off. They also have the ability to increase electrical current.
Extremely small transistors are used in computers. They form part of what is called an integrated circuit. Powerful integrated circuits have large numbers of transistors. Scientists have developed smaller transistors year after year to produce more powerful integrated circuits.
However, the new transistor may represent the smallest possible size for this kind of device. The area that carries electrical current in the new transistor is about the width of a single molecule.
Lucent Technologies' Bell Labs in Murray Hill, New Jersey, is developing the extremely small transistor. In Nineteen-Forty-Seven, scientists at the same laboratory invented the first transistor. William Shockley, John Bardeen and Walter Brattain received the Nobel Prize for Physics in Nineteen-Fifty-Six for their discovery.
Scientists Hendrik Schon, Zhenan Bao and Hong Meng created the new transistor. It is so small that it is put together chemically. The scientists used a chemical process to attach carbon-based molecules to gold. The process creates molecule-sized openings that carry electricity.
The molecules also chemically form a molecule-sized device that controls electrical current. Releasing and stopping electrical current permits electronic processors to move and store information. This simple ability to start and stop electrical current forms the language used by most computers.
The new transistor is still being developed. However, researchers at Bell Labs have already connected together several of the transistors into a circuit. They also say the chemical process for creating the transistors appears to work well.
Yet the new extremely small transistors may be too small. One scientist at Hewlett-Packard Laboratories worries that connecting so many molecule-sized devices together would prove to be almost impossible.
This SCIENCE IN THE NEWS program was written by Jerilyn Watson, Mario Ritter and George Grow. 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.