I found one site (http://extension.missouri.edu/xplor/wasteman/wm6004.htm) that says to flush it down the drain b/c it's flammable and toxic ("capable of causing injury or death through ingestion, inhalation, or absorption through the skin").
"'Flush down drain' indicates that a product can be poured down the drain with plenty of water. Contact your wastewater officials before pouring to determine if this recommendation is suitable in your area. If you have a septic tank, additional caution should be taken. Read the product label to determine whether the product might damage your plumbing or your septic system. If you are uncertain, see if the local wastewater plant will accept the product, or save it for a household hazardous waste collection. Never mix wastes while pouring them down the drain. Always pour small amounts at a time to avoid splashing, and flush with plenty of water."
Of course, another option is to donate them to a women's shelter.
