FAIRFAX, Va. (AP) - A professor who developed an inexpensive, easy-to-make system for filtering arsenic from well water has won a $1 million engineering prize - and he plans to use most of the money to distribute the filters to needy communities around the world.

The National Academy of Engineering announced Thursday that the 2007 Grainger Challenge Prize for Sustainability would go to Abul Hussam, a chemistry professor at George Mason University in Fairfax. Hussam's invention is already in use today, preventing serious health problems in residents of the professor's native Bangladesh.

After moving to the United States in 1978, Hussam got his citizenship and received a doctorate in analytical chemistry. The Centreville, Va., resident has spent much of this career trying to devise a solution to the arsenic problem, which was accidentally caused by international aid agencies that had funded a campaign to dig wells in Eastern India and Bangladesh.

The wells brought fresh groundwater to farmers and others who previously had been drinking from bacteria- and virus-laced ponds and mudholes. But the aid agencies were unaware that the groundwater also had naturally high concentrations of poisonous arsenic. As infectious diseases declined, arsenic-related skin ailments and fatal cancers began to increase - a problem that attracted much attention in the 1990s.

''I myself and all my brothers were drinking this water,'' said Hussam, who added that his family did not get sick, possibly because they had a good diet, which can help stem the effects of digesting arsenic.

Allan Smith, an epidemiologist at the University of California at Berkeley, said arsenic poisoning affects millions of people worldwide and it has been difficult to convince people that what seems to be good water might be toxic.

''You can't see it or taste or smell it,'' Smith said. ''The idea that crystal-clear drinking water would end up causing lung disease in 20 or 30 years is a little weird. It's unbelievable to people.''

Hussam spent years testing hundreds of prototype filtration systems. His final innovation is a simple, maintenance-free system that uses sand, charcoal, bits of brick and shards of a type of cast iron. Each filter has 20 pounds of porous iron, which forms a chemical bond with arsenic.

The filter removes almost every trace of arsenic from well water.

About 200 filtration systems are being made each week in Kushtia, Bangladesh, for about $40 each, Hussam said. More than 30,000 have been distributed.

Hussam said he plans to use 70 percent of his prize so the filters can be distributed to needy communities. He said 25 percent will be used for more research, and 5 percent will be donated to GMU.

The 2007 sustainability prize is funded by the Grainger Foundation of Lake Forest, Ill., and the contest was set up to target the arsenic problem. Among the criteria for winning was an affordable, reliable and environmentally friendly solution to the arsenic problem that did not require electricity.

Hussam's award will be presented Feb. 20 at Union Station in Washington.