The good news here is that LEDs do NOT contain mercury. Unlike fluorescent , compact fluorescent, and certain other lamps that DO contain small amounts of mercury with LEDs you do not have to dispose of them as hazardous waste.
There are laws governing the disposal of mercury containing lamps (particularly for large Users that dispose large amounts). If they end up in our landfills, contamination of soil and leaching into our streams and lakes has an adverse effect on fishes, etc. So, laws require proper re-cycling of mercury containing products.
With LEDs, they can be disposed of as standard waste. This further reduces costs for many Users and thus is a safe product. Just another benefit for using LEDs.