David Keith Priegel, age 10, of Okmulgee, Oklahoma, for his question:

Does electricity cause pollution?

Not directly. But indirectly certain methods used to generate electricity cause widespread pollution. Lightning is natural electricity that may or may not cause pollution. If it strikes a tree and starts a forest fire, it pollutes the air, the earth and streams for miles around. But most lightning merely helps to change the air's nitrogen into compounds that plants need to absorb.

Some of our electric generators are run by fossil fuels, others by nuclear reactors. The fossils, coal and oil and natural gas, often are allowed to foul the air with fumes and other dangerous pollutants. At present we are not certain whether reactors pollute the environment, how much or in what way. But we do know that generators powered by falling water, from dams or natural falls, cause no pollution. Very soon we hope to generate much of our electricity with geothermal energy. This natural energy in the earth's crust does not cause pollution either.