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

5 Exposure and risk assessment

• 5.1 Exposure levels
  • 5.1.1 Exposure scenarios
  • 5.1.2 Calculation method
  • 5.1.3 Calculation values
  • 5.1.4 Exposure calculations
• 5.2 Risk assessment
  • 5.2.1 Calculation method
  • 5.2.2 DNEL values
  • 5.2.3 Risk assessment scenario 1: Short-term exposure for 30 minutes
  • 5.2.4 Risk assessment scenario 2: Exposure over longer time
• 5.3 Summary and discussion

In this chapter theoretical concentrations to which consumers may be exposed if compact fluorescent lamps or straight fluorescent lamps break in the consumer’s private home are calculated. Then associated health risks are assessed.

5.1 Exposure levels

As described in the health assessment of mercury released from a broken fluorescent lamp, inhalation is the primary exposure route for mercury. Absorption through the skin of mercury vapours can happen to a limited extent, but since skin absorption only accounts for around 2-3 % compared with inhalation a calculation is only made of health risks from inhalation of mercury vapours from broken compact fluorescent lamps and straight fluorescent lamps.

Both the short-term exposure, e.g. during clean-up from an accident with breakage of a fluorescent lamp in the private home, and a long-term exposure in case, for instance, of insufficient cleaning exposing continuously consumers to mercury vapours, are interesting in a risk assessment context.

Therefore, relevant exposure levels for both short-term and long-term exposure are dealt with.

5.1.1 Exposure scenarios

The two exposure scenarios under assessment are two situations where exposure to mercury is highest. In the first situation a person picks up the broken compact fluorescent lamp and is exposed shortly to a high concentration of mercury.

In the second situation the broken compact fluorescent lamp is not completely cleaned up and thereby people are exposed to mercury for a longer period of time. For this scenario it is not possible to calculate the concentration of mercury in the home, since it depends on many factors such as ventilation, level of cleaning etc. In principle evaporation of mercury may take place as long as there are mercury residues in the room. Tests have been conducted where concentrations of mercury have been measured above the US RfC value (long-term concentration without harmful effects) of 0.0003 mg/m³ several weeks after breakage of a compact fluorescent lamp.

Following exposure scenarios are assessed:

• Scenario 1: A fluorescent lamp breaks and cleaning is done within 30 minutes. Exposure is calculated for an adult person. Concentrations are calculated with and without ventilation of the room.
• Scenario 2: Situation where cleaning after breakage of a fluorescent lamp is insufficient. Values measured in tests of breakages of fluorescent lamps are compared with various limit values.

5.1.2 Calculation method

For the short-term exposure scenario a model is used as presented in Chandrasekhar (2007) for how the mercury concentration in a room will fall over time after breakage of a fluorescent lamp when ventilation of the room is taken into account. Chandrasekhar has set up the following formula:

Where

Chandrasekhar assumes that the entire quantity of mercury from the lamp will evaporate immediately (time 0 min). This is found exaggerated since tests conducted by, among others, Aucott et al. (2003) showed that only a minor part (up to 7 %) of mercury in the lamp will evaporate within the first few minutes. Chandrasekhar furthermore assumes in the model that a fan is used. This fan contributes to ensuring that the concentration in the entire room is assumed to be the same – since heavy mercury vapours are otherwise naturally concentrated near the floor.

5.1.3 Calculation values

The following values are used for the calculation of the exposure scenarios. The values are explained in more detail below.

Table 5-1 Values used for calculation of exposure scenarios

Quantity of mercury Q_Hg

According to the Danish Environmental Protection Agency it is being considered at the moment to change the maximum permitted concentration of Hg in compact fluorescent lamps. It is being considered to reduce the present limit of 5 mg to 3.5 mg Hg or as low as 2.5 or 2 mg Hg per lamp. Similarly, new limits are being discussed for straight fluorescent lamps and for special forms of compact fluorescent lamps with levels of 7 mg Hg, 13 mg Hg, 15 mg Hg and as much as 40 mg Hg for compact fluorescent lamps/straight fluorescent lamps above 400 W. To reflect possible health risks associated with broken fluorescent lamps containing these new and revised amounts, calculations will be made with these values as well.

The existing limit for straight fluorescent lamps is at 5, 8 and 10 mg Hg respectively per straight fluorescent lamp depending on lifetime and phosphor added. Therefore, risk assessments will be made with these amounts as well.

The survey in connection with the present study has shown, however, that compact fluorescent lamps today have a content of mercury between 1.2 and 4.9 mg Hg per lamp, and straight fluorescent lamps have a content between 1.4 and 9.5 mg Hg per lamp. It is relevant to draw up risk assessments for these minimum and maximum values.

For the calculation the following values have therefore been used (since in practice no distinction is made between a compact fluorescent lamp and a straight fluorescent lamp):

• 1.2 mg, 1.4 mg, 2 mg, 2.5 mg, 3.5 mg, 4.9 mg, 5 mg, 7 mg, 8 mg, 9.5 mg, 13 mg, 15 mg and 40 mg Hg per lamp.

According to REACH Guidance Documents it should generally be assumed that 100 % of the mercury evaporates immediately. However, tests have shown that this would give an overestimated exposure.

Information from literature/industry shows that between 0.04 and 0.5 % of total mercury in the lamp will be in vapour form. As described it depends on temperature and inner volume of the lamp how large a quantity of mercury vapour is found in the lamp. Saturated mercury vapours have a concentration of 20 mg Hg/m³ at 25 °C. Sources from literature state amounts between 0.002 and 0.05 mg mercury in vapour form in a lamp. With the stated rates and the above quantities of mercury in a lamp this corresponds to between 0.0005 and 0.2 mg mercury. This quantity of mercury vapours within a lamp will disperse immediately in case of breakage. The mercury in the broken lamp can now evaporate further.

Experience from tests (Aucott et al., 2003) as described in Chapter 3 shows that around 10 % of total quantities of mercury in a fluorescent lamp will have evaporated within the first 30 minutes. However, this is subject to reservations for the following reasons:

• It is uncertain whether release of mercury depends on the type of amalgam used in the different lamps,
• Age of lamp may have an impact, and
• Not least, the concentration of mercury in the lamp has an impact on the release of mercury.

Despite these reservations a value of 10% is used in the calculations since it is found to be more realistic than a 100 % momentary release.

In practice, thus, a maximum of 0.5 % of total quantities of mercury will evaporate momentarily and in the subsequent 30 minutes up to around 10 % of total quantities of mercury in the lamp will evaporate (7 % already after a few minutes). For the worst-case calculations it is assumed, however, that the 10 % of the total mercury amounts will evaporate immediately when the lamp breaks.

Duration of exposure t

It is assumed that the cleaning scenario in the worst case lasts 30 minutes and that the person is exposed to the same concentration of mercury for all 30 minutes - corresponding to the initial concentration at the time 0. It is assumed for the long-term exposure that in the worst case it will be 24 hours per day in order to take into account homebound persons.

Volume of room V_room

It is stated in the ECHA Guidance Chapter R.15 (2008) that for short-term local exposure the volume of a room can be set at 2 m³ in order to represent the air immediately surrounding the exposed person. This value is used as the only value for the cleaning scenarios since mercury vapours are heavy, and the concentration of mercury in a room will be unevenly distributed where most mercury is found nearest to the place of breakage. According to, among others, Stahler et al. (2008) the concentration of mercury will be larger in, for example, 30 cm’s height than in 1.5 metre’s height. Thus, it will give an incorrect picture to “dilute” the mercury concentration on the entire volume of the room.

The 2 m³ immediately next to the exposed person can thus also be used as an estimate for the concentration in the lower 30-50 cm from the floor surrounding the place of the accident.

Ventilation A of room

The concentration of mercury in the room is calculated for three different rates of ventilation: No ventilation, normal ventilation and ventilation with all windows and doors open. No ventilation means an air exchange rate of zero and corresponds to a fictitive situation where the concentration is constant in the period of time applied. Normal ventilation is defined by the Danish Environmental Protection Agency as 0.6 times per hour. According to the ECHA Guidance Chapter R.15 (2008) air exchange in a room with all windows and doors open is at either 4.2 or 6.2 times per hour. Here, the most conservative value of 4.2 times per hour is used.

Thus, the following values for ventilation of the room are used:

• No ventilation – corresponding to 0 m³/min (note that this is a fictive value, since there will always be minor leaks in a house).
• Normal ventilation – corresponding to 0.02 m³/min for a volume of 2 m³ (room size x air exchange per hour / 60 minutes).
• Strong ventilation (all windows and doors open) – corresponding to 0.14 m³/min for a volume of 2 m³ (room size x air exchange per hour / 60 minutes).

5.1.4 Exposure calculations

5.1.4.1 Scenario 1: Short-term exposure for 30 minutes

As described above the short-term exposure is calculated with and without ventilation.

A calculation using the assumption of no ventilation is the worst case and a fictive calculation, since there will always be some leaks in a house.

The calculation of the concentration in the breathing zone during an accident with a broken compact fluorescent lamp or straight fluorescent lamp is done by dividing the quantity of mercury released from the lamp by 2 m³, which is the volume chosen for the breathing zone. The quantity of mercury released is calculated as 10 % of the total amount of mercury in the lamp (i.e. 1.2 to 40 mg). The results are shown in Table 5-2 below.

Table 5-2 Calculated concentrations in the breathing zone of mercury with a broken compact fluorescent lamp/straight fluorescent lamp in a room when it is assumed that only 10 % of total quantity of mercury will evaporate during the first few hours. The meaning of the green cells is discussed later.

Click here to see Table 5-2

To allow for the impact from ventilation the mercury concentration in the breathing zone has been calculated with the formula described in Chandrasekhar (2007). The concentration has been calculated for 13 different concentrations of mercury in compact/straight fluorescent lamps and for three different scenarios regarding ventilation (none, standard and all doors/windows open). Chandrasekhar uses a fan in his model to ensure that the concentration of the heavy mercury vapours is the same in the entire room. This will not be the case in practice, so in this study a small volume is used, corresponding to a breathing zone of 2 m³. Thus, it is assumed in the calculations that the mercury is not dispersed over the breathing zone of the 2 m³, which will be, for instance, around 30-50 cm just above the site of the accident in an area of 2-3 metres x 2 metres around the site of the accident. In the calculations it is assumed as above that only 10 % of the mercury of the fluorescent lamp will evaporate momentarily at the time 0.

5.1.4.2 Scenario 2: Exposure over longer time

Stahler et al. (2008) has shown in tests that even if cullet and mercury have been removed mercury concentrations above the USEPA long-term concentration without harmful effects (RfC = 0.0003 mg/m³) can be measured in the hours after breakage of a fluorescent lamp when windows and doors are closed again – even if there are no visible residues of the broken lamp. The same test also showed that it may take from a few days to more than 60 days before the concentration just above the floor dropped to below RfC.

The same study has also shown that mercury concentrations of up to 0.029 mg Hg/m³ can be measured several weeks after removal of lamp residues. These high concentrations were measured just above floor height and after vacuuming and impacting of the flooring material (simulation of walking/crawling on the floor). Carpets in particular seem to contain more ”mercury residues” after cleaning compared with wooden floors, but it is not difficult to imagine a wooden floor with large spaces that can easily collect as much mercury as a carpet. Thus, it is relevant to compare this value with the limit values for long-term exposure to mercury, even if it in this case is a high, short-term value that will drop when ventilation or airing brings down the concentration. The measured value of 0.029 mg Hg/m³ is thus not an expression of average concentration in the room.

Real-life tests conducted by Stahler et al. (2008) thus show that mercury residues can remain in the flooring for several weeks after the accident. It is not possible to calculate the concentration of mercury in the home based on the calculation formula from the ECHA Guidance Document Chapter R.15, since it depends on many factors such as ventilation and level of cleaning and the calculation formula does not take this into consideration. In addition it is uncertain for how long time mercury will evaporate. This would require more sophisticated calculations or use of, for instance, a computer model for calculation of consumer exposure, such as ConsExpo, as described in the REACH Guidance Document Chapter R.15. However, this has not been possible within the limits of this project.

In the following section the measured values are compared with relevant limit values for mercury at short-term and long-term exposure.

5.2 Risk assessment

5.2.1 Calculation method

For calculation of the risk of health-hazardous effects when a fluorescent lamp breaks the ECHA ”Guidance on information requirements and chemical safety assessment” (ECHA Guidance Chapter R.8 and R.15, 2008) has been used. These documents describe how to derive a DNEL^[10] value from a NOAEL or a LOAEL^[11] value.

The calculated DNEL value (endpoint specific) is calculated as:

Where

The risk is found by dividing the calculated exposure with the calculated DNEL value – and the so-called RCR value (Risk Characterisation Ratio) is thus calculated. If the exposure is larger than the DNEL value, there is a health risk for the calculated exposure scenario (RCR >1) (ECHA Guidance Chapter R.8, 2008).

For inhalation the DNEL value is stated in the unit mg/m³. This value is thus compared with the calculated exposure, corresponding to the concentration of mercury in the room (measured in mg Hg/m³), to which the consumer is exposed.

5.2.2 DNEL values

As described in the ECHA REACH Guidance Chapter R.8 (2008) the following types of (un)certainty factors should be used after correction for differences between experimental and expected human exposure conditions:

• Interspecies differences
• Intraspecies differences
• Differences in duration of exposure
• Issues related to dose-response
• Quality of whole database

Short-term exposure (DNEL_short)

As described in the health assessment in Chapter 4 no information about NOAEL values for short-term exposure to mercury is available. Most data on health effects from mercury vapours are derived from occupational exposures. At very high exposures to mercury vapours in the working environment the lungs are the target organ. At a few hours’ exposure to 1-3 mg Hg/m³ (1000-3000 µg/m³) acute fatal chemical pneumonia can occur. Even if the value of 1-3 mg Hg/m³ is a very high concentration of mercury vapour with very serious effects and even if the value is applicable for a few hours’ exposure and thus covers a longer period of exposure than for cleaning after breakage of a fluorescent lamp, the value of 1 mg Hg/m³ is used as the LOAEL value, since it is the lowest reliable value identified for short-term exposure.

The value is derived from occupational exposures in the working environment and the time of exposure is close to identical to the cleaning scenario, so the value of 1 mg Hg/m³ is used directly as the LOAEL value.

The LOAEL value is based on observations of humans, i.e. there is no (un)certainty factor (= 1) for interspecies differences. As standard is used a factor 10 as (un)certainty factor for intraspecies differences. For differences in duration of exposure no (un)certainty factor (= 1) is used since the LOAEL value is based on acute effects. For issues relating to dose-response the REACH Guidance Documents state an (un)certainty factor of 3-10 to convert from LOAEL to NOAEL, but it is stated that an (un)certainty factor of 3 should be used in most cases. For the quality of the whole database a further (un)certainty factor may be used. Altogether, an (un)certainty factor of 1 x 10 x 1 x 3 x 1 = 30 is used. This (un)certainty factor of 30 results in:

DNEL_short value = 0.033 mg Hg/m³ (33 µg Hg/m³).

This value, after calculation with the (un)certainty factors, is close to the Danish occupational threshold limit value, which is set at 0.025 mg Hg/m³ (25 µg Hg/m³).

Long-term exposure (DNEL_long)

Most data on health effects of long-term exposure to mercury vapours is derived from occupational exposure. Many existing limit values for mercury vapours are based on a LOAEL value of 0.025 mg Hg/m³ (25 µg Hg/m³ – identical to the Danish occupational threshold limit value). A recent study (Richardson et al., 2009) recommends LOAEL at 0.014 mg Hg/m³ (14 µg Hg/m³) for long-term exposure to mercury vapours.

A NOAEL value for long-term exposure of 0.010 mg Hg/m³ (10 µg Hg/m³) is used to determine the DNEL value since a LOAEL requires an additional certainty factor of at least 3.

The NOAEL value is converted to long-term exposure (as described in section 4.7) by multiplying with 5/7, as well as a factor 10/20 to take into account all seven days of the week and the total respiration volume of 24 hours. This gives 0.004 mg/m³ as the corrected NOAEL value for an exposure of 24 hours a day over a long period of time.

The NOAEL value is based on observations of humans, i.e. there is no (un)certainty factor (= 1) for interspecies differences. As standard is used a factor 10 as (un)certainty factor for intraspecies differences. For differences in duration of exposure no (un)certainty factor (= 1) is used since the NOAEL value is already based on chronic effects. For issues relating to dose-response it is stated that an (un)certainty factor of 3-10 can be used to convert from LOAEL to NOAEL. Here, it is not necessary to convert values, since it is a NOAEL value, so no (un)certainty factor is needed. For the quality of the whole database a further (un)certainty factor may be used. Altogether, an (un)certainty factor of 1 x 10 x 1 x 1 x 1 = 10 is used. This (un)certainty factor of 10 results in:

DNEL_long value = 0.0004 mg Hg/m³ (0.4 µg Hg/m³).

This value is close to the USEPA long-term reference concentration without harmful effects (RfC) of 0.0003 mg Hg/m³ as stated in Table 4-2.

5.2.3 Risk assessment scenario 1: Short-term exposure for 30 minutes

The short-term exposure is calculated above in section 5.1.4 ‘Exposure calculations with and without ventilation’ (see Table 5-2).

It is seen that the calculated concentrations in the breathing zone, regardless of quantities of mercury in the fluorescent lamp, exceed the DNEL_short value of 0.033 mg Hg/m³ (33 µg Hg/m³), when it is assumed that there is no ventilation in the room and assuming a momentary evaporation of 10 % of the total amount of mercury at the time t=0. This is an exceedance of around 2 to 60 times. With a content of 5 mg Hg in the lamp the exceedance is 8 times the DNEL_short value and 10 times the Danish occupational threshold limit value.

However, this calculation is as mentioned a worst-case calculation and a fictive calculation, since there will always be some natural ventilation.

In Table 5-2 are also stated calculated concentrations in the breathing zone, when ventilation is taken into account. The values marked by green background are below the DNEL_short value of 0.033 mg Hg/m³ (33 µg Hg/m³).

Calculations show that after 10 minutes’ ventilation with all doors and windows 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 thereby not constitute an acute risk. After 15 minutes’ strong ventilation the concentrations in the breathing zone will be below the DNEL_short value for compact fluorescent lamps with the presently permitted content of mercury (= 5 mg Hg), and after 30 minutes the mercury concentration is below the DNEL_short value for all calculated levels of mercury in compact fluorescent lamps and straight fluorescent lamps.

Thus, calculations show that with the assumption that 10 % of mercury has evaporated during the first 30 minutes the concentration of mercury in private homes will be above the DNEL_short value and thus constitute a risk – unless strong ventilation is ensured. Ventilation has a very significant impact in view of lowering concentrations of mercury down to non-hazardous levels in the home during an accident.

However, it should be noted that the DNEL_short value has been calculated based on a LOAEL value for an exposure of a few hours (not specified in more detail). In a cleaning scenario the cleaning time will probably only be about 10 minutes – in the worst case 30 minutes as assumed in the calculations. In case of fast clean-up the exposure time may be shorter than the one for which the DNEL_short value has been calculated and this means that the exposure to mercury in this shorter period of time is in reality much lower and thereby does not constitute a health hazard.

Generally, however, many factors have an impact on the assessment of the real risk:

• These calculations assume momentary evaporation at the time 0 and show how the concentration in the breathing zone decreases over time through strong ventilation.
• It is assumed that the concentration of mercury does not decrease during the first 30 minutes, which it will do when the source of contamination – the broken lamp – is removed.
• The distribution of mercury vapours in the room has not been studied in detail.
• It has not been studied in detail whether strong ventilation works just as efficiently on air exchange at floor level where mercury vapours are concentrated, as it does on air exchange higher up in the room. The Stahler et al. (2008) study shows, however, that ventilation from a window also has an effect on concentrations at floor height.

However, the tests show that a few minutes will pass before 7 % of mercury has evaporated and calculations show that 10-15 minutes’ strong ventilation can reduce concentrations significantly. It is thus important to pick up mercury quickly before too much of it evaporates. Coldness will reduce the rate of evaporation and heating will increase the rate of evaporation. It may be relevant to close doors to other rooms so that mercury vapours are not dispersed in the home.

Calculations are based on breakage of one fluorescent lamp. Thus, calculations indicate that if several fluorescent lamps break at the same time it will be necessary to ensure strong ventilation immediately and continue this ventilation for a long time after cleaning.

5.2.4 Risk assessment scenario 2: Exposure over longer time

Concentrations measured for a long period of time after breakage of a fluorescent lamp are stated above in section 5.1.4 ‘Exposure calculations’.

The measured peak value of 0.029 mg Hg/m³ is far above the DNEL value for long-term effects (0.0004 mg Hg/m³), but below the DNEL value for short-term exposure (0.033 mg Hg/m³). However, the values cannot be compared since the high experimental value was measured briefly in connection with, for instance, vacuuming and only just above floor height. The measured values are thereby not an expression of the average concentration in the room.

Stahler et al. (2008) showed however through tests that it may take from a few days to more than 60 days before the concentration just above floor height drops to below 0.0003 mg Hg/m³ – which is the US reference concentration (long-term concentration without harmful effects), which was used as a benchmark. Thereby, it cannot be excluded that there may be a risk of harmful effects (particularly for children crawling on the floor) after cleaning of a broken fluorescent lamp if there is not much focus to thorough and regular airing – also in the months after the accident.

Thus, experience from Stahler et al. (2008) shows that it is very important to continue airing after the accident – in particular in connection with cleaning and specifically if the accident happened on a carpet – also when it looks clean to the naked eye.

5.3 Summary and discussion

Short-term exposure

For the exposure scenario with 30 minutes’ exposure to mercury vapours during cleaning after breakage of a fluorescent lamp a LOAEL value of 1 mg Hg/m³ has been used to calculate the DNEL_short value. This LOAEL value covers a few hours’ occupational exposure and thereby a period of exposure longer than the assumed 30 minutes, though still relatively close to this.

Practical tests as described in Chapter 3 show that up to 7 % of the mercury in a fluorescent lamp evaporates during the first few minutes and that up to 13 % evaporates during the first 8 hours after breakage of a fluorescent lamp. Therefore it has been assumed that 10 % of the total amount of mercury in a fluorescent lamp evaporates within 30 minutes.

In the calculations it has been assumed that 10 % evaporates momentarily at the time 0 and that the resulting concentration is constant for 30 minutes, if there is no ventilation. Calculations show that with this assumption the concentration of mercury in the indoor air will exceed the DNEL_short value and thus constitute a risk. 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 low content of mercury (= 2,5 mg Hg), and thus not constitute an acute risk. After 15 minutes of strong ventilation the concentration in the breathing zone will be below the DNEL_short value for compact fluorescent lamps with the presently permitted content of mercury (= 5 mg Hg) and after 30 minutes the mercury concentration will be below the DNEL_short value for all calculated levels of mercury in compact and straight fluorescent lamps.

However, there are a number of uncertainties in the calculations; for example, momentary evaporation at the time 0 has been assumed, and the DNEL_short value is based on occupational exposure to mercury during a few hours. These uncertainties and assumptions in the calculations together with fast clean-up, for instance during 10 minutes, means that the exposure time will be significantly shorter than the 30 minutes’ period which again means that the resulting exposure is lower than calculated and does not constitute a health risk.

However, many factors play a role in the assessment of the risk in question. Thus, there are a number of uncertainties in the calculations, for example:

• The model assumes that the entire quantity of mercury (here 10 % of total quantities of mercury in the lamp) evaporates in the very instant of the accident since the calculations do not take into account the rate of evaporation. However, mercury evaporates quickly (7 % evaporated within a few minutes), so the overestimation is not large.
• It is assumed in the calculations that mercury vapours only disperse to the breathing zone of 2 m³ and not beyond this zone and that vapours are evenly distributed in this volume. This assumption may lead to an overestimation.
• The model assumes that the consumer is exposed to the entire quantity of mercury in the entire period of exposure – the 30 minutes it takes to clean up – though without the quantity reduced by ventilation. Thereby, the model does not take into account the fact that the concentration of mercury in the breathing zone will decrease as the source of exposure (the broken lamp) is picked up during the period of exposure.
• The model assumes that mercury vapours are evenly distributed through the use of a fan so airing will also lead to even ventilation of mercury vapours in the room. It has not been studied in detail whether strong ventilation is just as efficient for air exchange at floor height where mercury vapours are concentrated as for air exchange higher up in the room. However, the study by Stahler et al. (2008) shows that ventilation from a window also has an effect on concentrations at floor height.
• The DNEL_short value has been calculated on the basis of a LOAEL value for exposure for a few hours (not specified in more detail). In a cleaning scenario the cleaning time will probably be shorter – in the worst case 30 minutes as assumed in the calculations. In case of clean-up of, for instance, 10 minutes the exposure time will be significantly shorter and the resulting exposure lower than calculated.

Calculations are based on breakage of one fluorescent lamp. Calculations thus indicate that if several fluorescent lamps break at the same time it is necessary to ensure strong ventilation immediately. Generally, it is important to pick up mercury quickly and continue ventilation for a relatively long period after cleaning.

Long-term exposure

For the scenario with long-term exposure to mercury vapours in case of insufficient cleaning after a broken fluorescent lamp a NOAEL value of 0.010 mg Hg/m³ (10 µg Hg/m³) has been used to calculate the DNEL_long value.

This DNEL_long value is compared with measured levels from practical tests of broken compact/straight fluorescent lamps. In the tests cleaning had been done after the accident.

Calculations and a literature review also show that it is important to pick up mercury in case of an accident, since mercury remaining in a home may constitute a health risk.

The practical tests conducted by Stahler et al. (2008) showed that a cleaned-up home after breakage of a fluorescent lamp can still give off mercury to the indoor air for several weeks/months after the accident. In some cases it took several weeks before measured values had decreased to below the US long-term concentration without harmful effects (0.0003 mg Hg/m³) and under the calculated DNEL_long value of 0.0004 mg Hg/m³. Thus, it is also important to ensure extra ventilation after breakage of a lamp – particularly in connection with general cleaning/vacuuming of the home which may cause mercury-containing dust to be stirred up. Ventilation has a substantial impact in relation to lowering concentrations of mercury to non-harmful levels in the home after an accident.

[10] DNEL = Derived No Effect Level

[11] NOAEL = No Observed Adverse Effect Level, LOAEL = Lowest Observed Adverse Effect Level

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