Mercury Within Car Lights
For some time now mercury has been in used in the manufacture of automobile lights and headlamps. It helps improve light output and efficiency, for such a small amount of mercury that is not deemed by itself to be a health risk. When electricity is passed across electrodes using a vapour gas that includes mercury and other gases, then light is formed, in its most simplistic explanation.

However in small quantities it is deemed as safe, but from a business point of view where many lights are being decommissioned in one go, these lamps are seen as hazardous waste and must be treated in the regulations set out by the country concerned, in the UK’s cases it is currently EU regulations.
It is important to establish the difference between headlights and headlamps, or a cluster. What we see on the front of our automobiles, is often a large plastic reflector, with much smaller bulbs within, which hold the mercury. In older classic models, the whole of the headlight was sealed in a glass vacuum, but very few of these are around now. So in modern times, it is really the disposal of bulbs that are the hazardous factor.
Right Up To Date
A very modern replacement of the mercury bulb has been LED or Light emitting Diode lighting solutions. These look great on the front and many manufacturers have a specific design, so you can recognize who is driving what in the dark. It is hard to imaging that all models will not have LED lighting in the future.

Breaker Yard Disposal
There are specialist company that deal with the disposal of all mercury lighting included fluorescent bulbs used in domestic and commercial situations. In reality there is a bigger issue domestically that in the small bulbs used in the automotive industry, but it all adds up. Breaker yards have a responsibility to ensure bulbs are sent to these the specialist companies for disposal. However this will be done in bulk and over a period of time depending on how much stock comes through the yard.
Halogen Bulbs
Yes we know the term, these can be three times brighter than normal bulbs, but these options also contain mercury and should be included within the legal disposal process.
So what Would Happen If We Ignored Proper Disposal
Just throwing away light bulbs into a bin, would mean them ending up in a typical landfill site and over time mercury could then seep into our rivers or stream contaminating everything it comes into touch with. We have seen the affects of mercury contamination with water supplies before, so there can be no short cuts when it comes to correct disposal. One report that even a small amount of mercury found in a light bulb could contaminate up to 80,0000 litres of water, that is a sober thought.