We’d never heard this, can’t readily confirm it, doubt it and seek confirmation/debunking.
Ruby Gonzalez-Jimenez, LEED Green Associate, Expedient Energy asserts that:
Compact Fluorescent Light (CFL) bulbs do contain mercury, but only a small amount of between 1 to 4 milligrams (mg).
Mercury is the essential component of what allows a CFL to be an energy efficient bulb. CFLs are designed to seal the mercury tightly inside the glass tubing which prevents any release of mercury into its surroundings.
Two examples have been provided to demonstrate how small and practically insignificant the amount of mercury content in each CFL really is.
• Example 1: Mercury used in CFLs compared to traditional incandescent light bulbs
13 watt CFL contains 1.2 mg of mercury
60 watt incandescent (13 watt CFL-equivalent) contains 5.5 mg of mercury
• Example 2: Comparing mercury content in CFLs with mercury content in a thermometer
A CFL contains 1 to 4 milligrams of mercury
A thermometer (old fashion kind) contains 500 milligrams of mercury = amount of mercury in 125 CFLs
In comparison, the small amount of mercury present in each CFL does not make them a threat to the environment… [Emphasis added]