This biweekly column tries to answer some of the most commonly asked questions about recycling, composting and the town's solid waste program.

Q: I was looking for a product to remove rust stains from a shirt, and noticed one in the supermarket that claims to do the job but has poison warnings all over it and contains hydrofluoric acid! If I don't use the whole bottle do I have to take the rest to the hazardous waste site? Is there some less toxic alternative?
A: There are lots of items that are considered toxic/hazardous even though they are sold in supermarkets, hardware stores, and so forth. It should say on the label that they need to be treated as hazardous for disposal purposes, but often they only say "dispose of properly." Lots of these things (moth balls, drain cleaners, paint thinners, many others) keep for a very long time, so you could store them carefully and eventually use them up. In cases in which you only need a single use and have lots left in the container, you could try to find a friend who also needs that chemical and pass it on. For substances that you really won't use again and don't want to store, take them to the Household Hazardous waste collection site. The next day is Oct. 19. The Oct. 3 Lexington Minuteman had a lot of information about the products accepted, and there was a mailing from the town this summer also with information.

For rust stains, a frequent recommendation is oxalic acid, which is not benign either but is less scary than hydrofluoric acid. In either case, use heavy rubber gloves in a well ventilated place. It might be better not to buy toxic products in the first place.

Baking soda and vinegar (often in combination) can be used to replace a number of toxic products. For example, instead of a commercial drain cleaner, try pouring a half cup of baking soda down the drain followed by a cup of vinegar. Let it sit for a while, and then rinse with boiling water. Doing this regularly can help prevent clogging. A paste of baking soda and water can be used to scrub sinks and tubs, to clean out the inside of ovens, and other sorts of scrubbing. To clean brass, cut a lemon in half, sprinkle it with salt, and rub on the metal. Buff it with a cloth.