The introduction of CFLs has seen some emotive claims made about the perceived hazard from the mercury released from a broken bulb. We've looked at an extensive independent study into the health risks, and conclude that the tiny amount of mercury in a broken CFL is unlikely to be a health hazard.
What's the risk?
All CFLs contain very small amounts of mercury (less than 5mg), which is only released if the bulb is broken. The amount of mercury released depends on how used the CFL is – the amount reduces as the bulb ages.
Mercury is particularly toxic to children, pregnant women (and the baby they’re carrying), and people with kidney disease. When mercury vapour enters our bodies, it has a half-life of about 2 months. That is, it takes around 2 months for the mercury level to halve, another 2 months to halve again … and so on.
But how much mercury is toxic? The total amount that enters our bodies is dependent on the combination of the mercury concentration level and the exposure time.
Safe concentration levels have been established by several overseas studies. It varies with the exposure time and for continuous lifetime exposure the concentration level is much lower than for short durations.
The Ministry study
We were planning to do our own testing of the health hazards from broken CFLs – but when we heard in late 2008 of a study being conducted by the Ministry of Health we decided our test would be a waste of resources.
The Ministry’s study looked at 2 broken-CFL scenarios. In the first, mess from the broken bulb wasn’t cleaned up and the room wasn’t ventilated. In the second, the mess was cleared up and the room was ventilated by opening the window.
Mercury vapour concentration levels were measured 15, 30 and 60 minutes after the breakage at the breathing levels for a child (300mm above the floor) and an adult (1500mm).
The study concluded that:
- “The averaged one hour concentrations were not likely to be a health risk - even if the broken bulb was not cleaned up immediately”; and
- “adequate ventilation and clean up results in lower mercury concentrations”.
For both scenarios “human health risk is unlikely”.
The report can be downloaded from the Ministry of Health website.
Who did this study?
The study was performed by US-based Toxicology Excellence for Risk Assessment (TERA), under contract to the Institute of Environmental Science and Research Limited (ESR) and the New Zealand Ministry of Health.
TERA’s business is to “protect public health by developing and communicating risk assessment values, improving risk methods through research, and educating the public on risk assessment issues.”
… “this assessment was conducted by an independent, non-profit organisation, using state-of-the-science chemical risk assessment methods to protect public health”.
TERA used data from several different laboratory experiments where CFLs were broken in a controlled environment and the mercury-vapour concentrations measured over time.
- Consumer endorses CFLs as a way of reducing household energy bills and the CO₂ emissions from electricity generation.
- Be careful when handling CFLs – try not to break them. Don't use excessive force and try to hold the CFL bulb by the base and not the tubes when fitting it.
- Don't use them in places where they are likely to get broken.
- If a breakage occurs, children and pregnant women should stay away from the room. Ventilate the room and use the recommended clean-up procedures.