Numerous bits of orbiting debris threaten spacecraft, so two teams propose tracking them with unique license plate-like transponders.
Mixtures of chemical pollutants may harm people and wildlife, even when each chemical is below its regulatory threshold.
Low oxygen areas are disappearing almost a month earlier than they did 30 years ago.
Nationwide study shows how manufacturing facilities can increase levels of medical compounds in waterways.
Researchers found that efforts to curtail tourism-related emissions have been outpaced by the industry's growth.
Ambitious plan aims to keep waste out of rivers without massive new pipes.