Accumulation of man-made junk in Earth's orbit could render some well-traveled pathways too risky to use and may imperil the space shuttle and planned space station, a congressional report warned Thursday.

"Unless nations reduce the amount of orbital debris they produce each year, future space activities could suffer loss of capability, loss of income and even loss of life as a result of collisions between spacecraft and debris," the Office of Technology Assessment said.So-called space junk includes deactivated spacecraft, spent rocket stages, fragments of spacecraft and their equipment, paint flakes, engine exhaust particles and spent Soviet reactors, the report said.

In the vacuum of space, objects stay in orbit for a very long time. Even tiny objects, like a snippet of wire, can inflict considerable damage if they strike spacecraft at high speeds.

"Continued steady growth of orbital debris could by 2000 or 2010 render some well-used low-Earth orbits too risky to use," the OTA said.

The congressional analysis offered no exact estimate of the amount of man-made debris currently orbiting Earth. However, they noted some experts estimate there may be 30,000 to 70,000 bits of debris 0.4 inches in diameter or greater, and many more smaller objects are thought to be in orbit.

"Neither the number nor the distribution of these objects is sufficiently well known to predict which methods of protection would be most cost-effective," the 64-page report said.

It said out that the tiny paint chip that damaged the shuttle Challenger's windshield in 1983 probably would have had the power to puncture the spacesuit of an astronaut who happened to be conducting a maneuver outside a spacecraft.

If space-faring nations and organizations took a number of "relatively simple preventive measures," the steady growth in production of man-made space junk could be greatly reduced, the OTA said.

Such steps include designing launch vehicles and spacecraft so they have minimum potential for breaking up, protecting spacecraft batteries from shorts that can cause explosions, and reducing the altitude of spent rocket stages to the point where atmopsheric drag effects will bring them down.