EPA’s 1997 study estimated about 1.5 tons per year of mercury emissions from lamp breakage (in 1994-1995), out of a total of 158 tons.
Now another chunk of mercury comes from lamps that are thrown in the garbage and subsequently incinerated. My rough guess is about another 1.5 tons, so say 2 percent of the total.
The gross amount has probably risen since 1995, as more flourescent bulbs are used. Nobody seems to have found a substitute yet, and even though manufactureres may be using a little less per bulb, there are a lot more bulbs being made.
Whay are people unaware? Well, the best answer is that making individuals aware of it hasn’t been a priority for government agencies or (very much) for environmental groups. Even the little mercury in a flourescent bulb is a Bad Thing, but it would be a big effort to enforce haz waste regulations for individuals tossing a single bulb and/or convince them not to do it voluntarily. And saving energy by using more efficient bulbs is in general a Good Thing. So the effort has been deemed (I think rightly) not worth it.
As opposed to educating and/or enforcing haz waste laws for large facilities, where you only need to reach one person to affect thousands of bulbs a year. This government agencies have done and, as previous posts demonstrate, most large facility managers are getting the message about proper disposal of mercury bulbs.
Many agencies have been working on educating individuals about mercury thermometers (and to a lesser degree thermostats and other switches). These have a LOT of mercury compared to a light bulb, so it’s a little better use of resources to try and teach people about them.
So bottom line: it’s an environmental hazard, but not the biggest hazard we’re facing right now, so groups with limited resources have focused on other things.