6 Discussion and conclusion

Survey and health assessment of mercury in compact fluorescent lamps and straight fluorescent lamps

Mercury is a metal that is liquid under normal pressure and temperature and it appears as a heavy, odour-free silvery liquid with a relatively high vapour pressure at room temperature. Particularly mercury vapours constitute a health problem since large parts of mercury vapours are absorbed through the lungs during inhalation whereas absorption of the poorly soluble and inert metallic mercury through the skin and the gastrointestinal tract is minimal. Furthermore, mercury vapour can also easily pass the blood-brain barrier and the placenta barrier and can in that way have an impact on the central nervous system and the unborn child. Long-term exposure of the central nervous system can lead to symptoms such as tremor and memory loss.

In fluorescent lamps mercury is used either in the form of a HgFe compound, as amalgam or in the form of metallic mercury. This mercury in solid or liquid form will be in equilibrium with mercury in vapour form. Therefore, a small quantity of mercury in vapour form will be present within the lamp and this mercury vapour causes, among other substances, the lamp to light.

If one or more fluorescent lamps break in a home invisible and odour-free mercury vapour is released to the indoor air as long as the residues from the lamp/-s have not been completely removed. Mercury vapour is seven times heavier than air and will disperse along the floor in a room with insufficient ventilation.

In this study it was investigated whether the quantities of mercury present in fluorescent lamps constitute a health risk if a lamp breaks in a home. Assessments have been carried out of risks in the short term (30 minutes’ cleaning) and in the long term in the event of insufficient cleaning after breakage of a lamp.

A worst-case calculation has been made of concentrations of mercury vapour in the breathing zone during accidents with a broken lamp with different contents of mercury. These calculations, which also take into account ventilation, show that concentrations of mercury in the breathing zone during cleaning exceed the DNEL_short value (calculated concentration without effects), which means that there may be health effects when exposed to mercury vapour. The calculation model, however, is subject to several uncertainties. The calculations are worst-case calculations and the DNEL_shortvalue has been calculated based on data for an exposure time of a few hours. In addition, the calculation model shows that strong ventilation is an important factor in terms of bringing down the level of mercury vapour to a non-health hazardous level in the breathing zone. Removing the source of contamination – the broken lamp – as fast as possible also has a substantial impact.

Therefore the conclusion is that when uncertainties and assumptions are taken into consideration there is no risk of health effects through short-term exposure to mercury when a mercury-containing lamp breaks if residues are picked up immediately and ventilation is ensured.

Evaporation of mercury will take place as long as there are still mercury residues present in the room.

For prolonged exposure to mercury in a home it has not been possible within the frames of the present project to make a calculation of the concentrations of mercury in a home since it depends on many factors such as ventilation, level of cleaning etc. Therefore, a DNEL_longvalue has been compared with concentrations of mercury vapour measured in tests conducted after cleaning of broken fluorescent lamps. These concentrations derive from various tests found in a literature study.

Literature describes that it has been demonstrated in practical tests that a cleaned-up home after breakage of a fluorescent lamp can still release mercury vapours for several weeks/months after the accident. In some cases it took several weeks before measured values just above floor height were below DNEL_long value. Thereby crawling children may be exposed to concentrations with health-hazardous effects in the long-term perspective. In connection with general cleaning/vacuuming in a home mercury-containing dust may be stirred up.

Thus, the conclusion regarding exposure to mercury vapours in the long term is that there may be a risk of health effects in case ventilation and removal of all mercury-containing residues (i.e. thorough cleaning) is not ensured. Thorough cleaning after breakage of the lamp is thus important and so is ventilation for a long period, since mercury vapours may be released from invisible residues of the broken lamp.