To put it simply, they are the residues of potentially harmful substances you use in your home. One litre of motor oil can contaminate two million litres of drinking water. You can't treat hazardous wastes like other kinds of garbage. Buried wastes can filter down through the soil and contaminate groundwater.
Wastes can clog storm sewers and over-burden septic systems.
Plumbing systems can be damaged by corrosive chemicals. Burning hazardous wastes may simply distribute them over a larger area. Pouring hazardous liquids on the ground can poison soil, plants and water. Products labelled as corrosive, flammable, reactive or toxic should be disposed of only at a hazardous waste facility. Even if they don't have warning labels, it's safe to assume that products like paint, motor oil and old propane tanks are potentially hazardous too.