Summary and conclusions

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

Compact fluorescent lamps contain small quantities of health-hazardous mercury
What is mercury
Forms of mercury in compact and straight fluorescent lamps
Why is mercury a health problem?
Calculation of level of mercury vapours without harmful effects
Which levels can be found after breakage of lamps in a home in the short-term perspective?
Which levels can be found after breakage of lamps in a home in the long-term perspective?

Compact fluorescent lamps contain small quantities of health-hazardous mercury

Compact fluorescent lamps represent one of the most efficient solutions available today to improve energy efficiency of house lighting – but compact and straight fluorescent lamps contain small amounts of the element mercury, which is hazardous to health. With this project, the Danish Environmental Protection Agency will examine whether there is a health risk associated with breakage of a compact or a straight fluorescent lamp in a private home.

Therefore, the following is examined

types of compact and straight fluorescent lamps on the Danish market for private use, and
quantities of mercury and mercury compounds in these fluorescent lamps.

Based on this information, a theoretical risk assessment is made of a potential accident with breakage of a fluorescent lamp emitting mercury vapour in a private home.

The assessment is made partly as a theoretical calculation of quantities of mercury that expectedly will evaporate, when a compact fluorescent lamp or a straight fluorescent lamp breaks in a home; and partly through an assessment of measured concentrations in a home in the weeks after an accident with breakage of a compact fluorescent lamp. Concentrations are compared with known values for concentrations where health hazardous effects have been seen.

The project has been commissioned by the Danish Environmental Protection Agency and carried out but FORCE Technology in the period from December 2009 to May 2010.

What is mercury

Mercury is a metallic element appearing as a free metal as well as in inorganic and metal organic compounds. Furthermore mercury can be mixed with other metals to form amalgams. Mercury (Hg⁰) is the only metal which is liquid under normal pressure and temperature, and it appears as a heavy, odour-free silver liquid with a relatively high steam pressure at room temperature. Handling of liquid mercury will therefore mean exposure to invisible and imperceptible mercury vapours. Mercury vapours are seven times heavier than air and will disperse along the floor in a room with insufficient ventilation.

Forms of mercury in compact and straight fluorescent lamps

In compact/straight fluorescent lamps mercury is used either in the form of a HgFe compound, in the form of amalgams or in the form of metallic mercury. This solid or liquid mercury species will be in equilibrium with mercury as vapour. There will be a small quantity of mercury as vapour inside the fluorescent lamp, and that, among other factors, causes the lamp to light.

If one or more compact or straight fluorescent lamps break in a home, mercury vapours will be released to the indoor air as long as residues of the lamp have not been completely removed.

Consumers will be better protected against exposure to mercury in the lamps, if the lamps use encapsulated mercury (in the form of a tablet or as amalgam) compared with the use of liquid mercury – for the very reason that the mercury will be bound.

Why is mercury a health problem?

Mercury vapours are toxic and a health problem, because the vapours are extensively absorbed through the lungs during inhalation. In contrast, absorption is low of the poorly soluble metallic mercury through the skin and from the gastrointestinal tract. Furthermore, mercury vapour readily passes the blood-brain and the placental barriers, and it can in that way have an impact on the central nervous system and the unborn child.

Most data on health effects of mercury vapour originate from occupational exposures. The lungs are the target organs at very high exposures to mercury vapours as in the working environment. The effects are irritation and corrosion of the respiratory tract, and at a few hours of exposure to 1-3 mg Hg/m³ (1000-3000 µg Hg/m³) a fatal acute chemical pneumonia can develop. There is immediate danger to life and health at exposure levels of about 10 mg Hg/m³ (10,000 µg Hg/m³).

At prolonged high exposure to mercury vapours at levels of > 0.100 mg/m³ (>100 µg/m³) the critical organ is the central nervous system. At these levels serious damage with classical poisoning symptoms such as tremor, insomnia, depression, mental unbalance, irritability, memory loss, abnormal shyness and gingivitis can be expected.

Minor acute toxic effects (such as hand tremor or memory loss) in humans can be anticipated at long-term exposure to 0.025-0.050 mg Hg/m³ (25-50 µg Hg/m³). This value of 0.025 mg Hg/m³ (25 µg Hg/m³) is identical to the Danish occupational threshold limit value and the Threshold Limit Value (TLV) by the American Conference of Governmental Industrial Hygienist (ACGIH).

Calculation of level of mercury vapours without harmful effects

Based on a health assessment of mercury vapour DNEL values (Derived No Effect Level) of both short-term (30 minutes’ clean-up) and long-term (if a proper clean-up has not been carried out after an accident with a broken lamp) exposure have been calculated in this report. The calculated DNEL values for short-term (DNEL_short value = 33 µg Hg/m³) and long-term (DNEL_long value = 0.4 µg Hg/m³) exposure are close to the Danish occupational threshold limit value (25 µg Hg/m³) and the USEPA Reference Concentration (RfC) – a long-term concentration with no harmful effects (0.3 µg Hg/m³), respectively.

LOAEL (Lowest Observed Adverse Effect Level) and NOAEL values (No Observed Adverse Effect Level) used for the calculation of the DNEL values in this project, as well as the different threshold limit values that exist for mercury vapour, are all based on observations from the working environment of adult humans and their exposure to mercury vapours. As the documentation is based on occupational exposure, it is not known whether children are more sensitive to exposure to mercury vapours. However, children are generally considered more sensitive than adults towards toxic effects. Children have a lower respiration volume than adults and will therefore inhale smaller amounts of the toxic mercury vapours, but children also have a lower body weight than adults. Furthermore, their nervous system is under development, and as described in Chapter 4 the critical organ at prolonged high exposure to mercury vapours is exactly the central nervous system. No assessment has been made in this project whether these concentrations will present a special risk to children that are present in a room where a fluorescent lamp breaks. The DNEL values have, however, been calculated by use of a safety factor of 10 thus accounting for individual differences between humans. This safety factor should therefore account for the fact that children are more sensitive than adults towards toxic effects. However, information has been found showing that exposure to mercury vapours is a special risk for pregnant women, since mercury vapours can pass the placenta barrier and harm the unborn child.

The calculated DNEL values are then compared to the calculated worst-case concentrations during clean-up and to concentrations measured in tests after clean-up of broken fluorescent lamps. These concentrations derive from different tests found in literature.

Which levels can be found after breakage of lamps in a home in the short-term perspective?

For the calculation of short-term exposure (30 minutes’ clean-up), a calculation model has been used that accounts for ventilation in the room. The calculation model uses a specific measure for the volume of air surrounding the exposed person – in this report called the breathing zone. This specific measure has been taken from the ECHA Guidance Chapter R.15 (2008), which describes that for short-term local exposure the volume of air immediately surrounding the person can be set at 2 m³. The calculations show the following:

No ventilation: By using the assumption that 10 % of the mercury has evaporated during the first 30 minutes, the concentration in the room without ventilation will exceed the DNEL_short value and thereby present a health risk – regardless of the amount of mercury in the lamps. Calculated concentrations of mercury vapours (for =5 mg Hg in a compact fluorescent lamp) exceeding the DNEL_short value with up to 8 times have been calculated. This is, however, an overestimation as no ventilation (zero) is a fictive value since this corresponds to a theoretical air tight room with no ventilation through cracks and fissures.
Ordinary ventilation: Is slow reduction of concentration of mercury vapours in the room. It will take up to two hours before the concentration of mercury vapours in the breathing zone falls below the DNEL_short value at an ordinary ventilation rate – and if only one lamp is broken (for =5 mg Hg in a compact fluorescent lamp).
Strong ventilation: Is of significant importance with respect to reducing concentration of mercury to non-harmful levels in the home after accidents. After 10 minutes of ventilation with all windows and doors open, the mercury concentration in the breathing zone of 2 m³ will be below the DNEL_short value for compact fluorescent lamps with a low content of mercury (=2.5 mg Hg), and will therefore not present an acute risk. After 15 minutes of strong ventilation, the mercury concentration in the breathing zone is below the DNEL_short value for compact fluorescent lamps with the presently permitted content (=5 mg Hg), and after 30 minutes the mercury concentration is below the DNEL_short value for all calculated contents of mercury in fluorescent lamps.

The calculations are based on an accident with one single compact or straight fluorescent lamp. The calculations thereby indicate that if more than one lamp breaks, the evaporation of mercury is larger, and thus the need for ventilation is greater.

However, the calculations are subject to many uncertainties. Amongst others:

The calculation model assumes that the entire amount of mercury (here 10 % of the total content of Hg in the lamp) evaporates instantly, when the accident happens, as the calculations do not account for the evaporation rate. Mercury does, however, evaporate quickly (7 % evaporates within a few minutes), and therefore the overestimation of using 10 % is not high.
It is assumed in the calculations that mercury vapours only disperse within the breathing zone of 2 m³ and not beyond this area. It is also assumed that the vapours are distributed evenly inside this volume. That assumption can cause an overestimation.
The model assumes that consumers are exposed to the entire amount of mercury during the entire time of exposure – i.e. the 30 minutes it takes to clean up (except the amount of mercury that is removed through ventilation). Therefore, the model does not account for the fact that the real concentration of mercury in the breathing zone will be lower, if the exposure source (the broken lamp) is removed from the room before the end of the exposure time. If the mercury and lamp residues are removed quickly, the calculations are hence overestimated.
The model assumes that mercury vapours are evenly distributed by use of a fan, and therefore ventilation of the room will result in an even ventilation of the mercury vapours in the room. It has not been investigated further, whether strong ventilation is as effective regarding air exchange near the floor, where the mercury vapours are concentrated, compared with air exchange higher in the room. However, investigations show that air exchange from a window also has an effect on the concentration of mercury near the floor.
The DNEL_short value is calculated by use of a LOAEL value for an exposure for a few hours (not specified further). It is assumed in this report that clean-up in the worst case will take 30 minutes. If clean-up is quick, e.g. 10 minutes, the exposure time will be significantly shorter, meaning that the exposure will be significantly lower than calculated.

When the uncertainties and the assumptions of the calculations are taken into account, the conclusion is that there is no health risk associated with a short-term exposure to mercury vapour released, after breaking a fluorescent lamp in a home, provided that lamp residues are removed quickly, and the room is ventilated immediately.

Which levels can be found after breakage of lamps in a home in the long-term perspective?

This is a situation where not all residues of the broken lamp are removed and therefore people can be exposed to mercury vapours in a prolonged time period. For this scenario, it has not been possible to carry out a calculation of the concentration of mercury vapours in the room, as it depends on many factors, such as ventilation, how well clean-up has been performed etc. Evaporation of mercury can in principle continue as long as residues of mercury are left in the room.

Consequently, the calculated DNEL_long value has been compared with concentrations of mercury vapours measured in various studies with broken lamps described in literature.

These studies show that mercury from a broken lamp can evaporate in a cleaned-up home for several weeks/months after the accident. In some cases it took several weeks before the measured values were below the US long-term concentration without harmful effects of 0.0003 mg Hg/m³ (0.3 µg Hg/m³) and thereby also under the calculated DNEL_long value of 0.0004 mg Hg/m³ (0.4 µg Hg/m³).

Extra ventilation after an accident is therefore important – especially in connection with ordinary cleaning/vacuuming in the home, which can cause mercury-containing dust to be stirred up. Ventilation has a substantial effect in terms of lowering mercury concentrations to non-harmful levels in homes after accidents with a broken fluorescent lamp.

For long-term exposure to mercury vapours the conclusion is that if all mercury residues are not removed properly (i.e. thorough clean-up), they may constitute a health risk. Thorough clean-up soon after the accident will remove most of the mercury. Furthermore, it is important to continue ventilation after an accident, as mercury vapours can be released from non-visible residues of the broken lamp for several weeks/months after the accident.