*Throw it in the trash. Some hazardous wastes in small amounts are acceptable at some landfills. Generally, you can dry out the substance. Paint can be dried with newspapers.
*Flush it. Using plenty of water, some hazardous substances can be put down your household drain. The toilet is recommended because it instantly dilutes the product and it is away from food preparation areas. One rule: Never mix chemicals together. Wait at least two hours between flushing ammonia and bleach to avoid a chemical reaction.
*Recycle it. If you have leftover paint, donate it to your church or a theater group. Paint thinner can be reused if the sludge settles out from the bottom and is discarded.
*Save for hazardous waste handler or reclaimers. Four quarts of motor oil can be reprocessed into 2.5 quarts of reusable oil. When you buy a new automobile battery, ask the store if they take back old ones. Leftover pesticides can be diverted to garden clubs, landscapers or exterminators. Call your local extension service for names of others who will use up pesticides.
In terms of waste handlers, two places that can direct you are the Maryland Environmental Service, (800) I RECYCLE, and the University of Maryland Cooperative Extension Service, (301) 454-3742.
If you are cleaning out an old house or your grandmother's basement, or renovating a building, and there are cans or bottles of unmarked chemicals left behind, do not dispose of them until you get professional advice.
"You may find insecticides left by someone who used to do extermination on the side years ago," says Ralph Cullison, chief of the Environmental Services Division, of Baltimore's Department of Public Works. Chlordane, which is now banned, is one such old termiticide that is highly toxic and should be handled with care.
"For those types of chemicals, you can call the City Health Department for information on how to dispose of it," says Mr. Cullison.