Surprise! More Than Twice As Much Mercury In Environment As Thought
sciencehabit writes The most comprehensive estimate of mercury released into the environment is putting a new spotlight on the potent neurotoxin. By accounting for mercury in consumer products, such as thermostats, and released by industrial processes, the calculations more than double previous tallies of the amount of mercury that has entered the environment since 1850. The analysis also reveals a previously unknown spike in mercury emissions during the 1970s, caused largely by the use of mercury in latex paint.
A bit of calculation will show that CFLs are likely to save more mercury by decreasing the amount of coal burned, even if you smashed each one on the ground at the end of life. A huge fraction of anthropogenic environmental mercury comes from burning coal. Overall, they are almost certainly a net reduction in anthropogenic mercury. I don't think they're great, but they are a reasonable stop-gap solution until LEDs take over.