You've rummaged through the fridge and found a package of luncheon meat hiding in the back with an expiration date for sometime last month. The same applies to garden chemicals stored over the winter.
Most cities have a hazardous materials waste disposal procedure for pesticides.
Check with your water department to see if one is available in your city. As always, it's best if you can use all the chemicals before the season ends. Do the same when purchasing or using biological controls for use in the garden. Predatory mites, for example, can live only a few days inside their shipping container. They should always be mailordered using express mail services.