Household Chemicals, Old Medicine Etc

[lingling]

Over the years some things tend to pile up; expired medicine (both OTC and prescription), various household chemicals, old engine oil and other automotive fluids. In the west there are established ways to properly dispose of these; expired medicine can be returned to pharmacies, old engine oil returned to the auto part stores, radiator fluid/antifreeze flushed down the toilet etc. How about in Thailand, how do one dispose of these things properly here? Flushing down medicine and/or household chemicals is obviously a bad idea since it will not only upset the biological balance in the septic tank but potentially add to environmental damage. So... what is the proper way to dispose of these items here?