This comes from our friends at www.SafeMinds.org
"The Coalition for SafeMinds is a non-profit organization founded to scientifically investigate, support research, raise awareness, change policy and focus national attention on the growing evidence of a link between mercury and neurological disorders such as autism, attention deficit disorder, language delay and learning difficulties."
SafeMinds frequently provides us with updated information on the issues regarding mercury in CFL products. Below is the best explanation we have seen regarding the claim that there is only a "small amount of mercury in a CFL bulb". Although the average amount of mercury in a CFL is 4mg - SafeMinds does the following analysis based on the impact of just 2.5mg.
"It's A Small Amount"
A Message from SafeMinds President, Theresa Wrangham
One argument that is often made about compact fluorescents is that they only contain a "small amount of mercury". Current CFLs typically contain less than 5mg (not mcg) of mercury. Some contain as "little" as half of that or 2.5 mg. Let's put that number in perspective:
There are 1000 mg in a gram so 400 CFLs contain a gram of mercury. A gram of mercury (about 1/70th of a teaspoon because mercury is very heavy) is enough, if vaporized, to contaminate a 20-acre lake for a year to the point where the fish are unsafe to eat. Now consider the fact that in 2007 the EPA estimates that 380 million CFLs were sold. Those bulbs contained enough mercury to make 950,000 lakes toxic! This is by no means a "small" amount of environmental mercury.
Now let's look at the "small" amount of mercury in a single compact fluorescent assuming that it just broke in your home. Again, we take a CFL containing 2.5mg of mercury but this time we convert it to nanograms, which are billionths of a gram. 2.5mg= 2,500,000 nanograms of mercury.
A typical 12'x14' room with an 8' ceiling contains 38 cubic meters of air. If you divide these numbers you get an air concentration of 65,789 nanograms of mercury per cubic meter of air. For argument's sake, let's assume that only a 10th of the mercury in that CFL actually vaporized (which is conservative based on the published data), so now you are down to 6,579 nanograms per cubic meter of air. Next, let's look at some of the safety reference ranges that the government has established:
300 nanograms per cubic meter of air - this is the Environmental Protection Agency's reference concentration for chronic occupational exposure to mercury vapor in adult males.
200 nanograms per cubic meter of air - this is the Agency for Toxic Substances and Disease Registry's Minimal Risk Level for chronic exposure in adult males. They have also established a re-occupancy level of 1000ng/cubic meter; this is the level at which it is safe for people to re-enter a building that has been contaminated with mercury.
Both of these reference ranges have safety factors of 30 built into them. One single CFL, when broken, produces an air concentration of mercury roughly equivalent to the level that is known to cause neurological effects in adults
90 nanograms per cubic meter of air - this is California's Reference Exposure Level to prevent mercury damage to the developing brain based on animal studies. In our conservative example a broken CFL exceeds this reference range by 73 times!
Obviously, the amount of mercury in the air will dissipate over time, but this assumes that the homeowner knows that there is mercury in the CFL and cleans up and ventilates appropriately. At SafeMinds, we would rather be cautious and consider the "what if" scenarios:
"What if the homeowner is a pregnant woman?"
"What if the bulb breaks in a toddler's bedroom - or a daycare?"
"What if someone drops a multi-pack of bulbs?"
"What if the room has no windows to ventilate through?
"What if the broken bulb gets left in the trash can for a week?
"What if the homeowner doesn't have a clue that they have a neurotoxin on the floor?"
Even a "small amount" of mercury should not be taken lightly.