9. Action Values and Temporary Abatement

This section discusses the recommended action values stipulated by the Danish Health Authority and the Danish WEA in relation to elevated exposure levels of PCBs in the indoor climate and temporary abatement.

It is the duty of the building owner to ensure that a building does not pose a health risk to the residents or occupants. This also applies if there are PCBs in the indoor air constituting a health risk to residents or occupants of the building (Danish Government, 2011). The local authority decides whether occupying a building constitutes a health risk (Ministry of Transport and Housing, 2015). The local authority has a duty to initiate an investigation when there is reason to suspect PCBs. Based on the results, they are duty bound to decide whether occupancy is associated with health risks (www.pcb-guiden.dk).

It is the duty of the employer to ensure a safe and healthy working environment in the workplace. This implies that e.g. PCB-containing caulk in the building should not off-gas or emit dust in quantities adverse to health in rooms where work is carried out (Danish Government, 2011). Pursuant to provisions of working environment legislation, the Danish WEA can intervene if it comes to their attention that a workplace is adverse to the health of its occupants (Ministry of Employment, 2010).

The Danish Health Authority and the Danish WEA’s recommended action values are described in Section 1.3.5, Recommended Action Values. The Danish Health Authority’s recommended action values for PCB concentrations in indoor air are graduated into two categories: 300-3,000 ng/m3 and above 3,000 ng/m3. The Danish WEA’s action values are graduated into three levels: 1,200–3,000 ng/m3; 3,000–10,000; and above 10,000 ng/m3.

The Danish WEA’s action values do not apply to the work involved in PCB remediation nor to demolition work where interventions are made to address building parts and materials. Managing PCB-containing materials requires special working environment measures (see SBi Guidelines 242, Renovering af bygninger med PCB, 3 Beskyttelse af mennesker og miljø (Renovating Buildings Containing PCBs, 3 Protecting People and the Environment) (Andersen, 2013b).

If the preliminary investigations and mapping of indoor air have indicated elevated concentrations of PCBs, one should assess whether to take further action and/or investigation (measurements of PCBs in indoor air and a follow-up or full mapping of all potential PCB sources in the building materials). Implementing temporary abatement while further mapping is in process is recommended (see SBi Guidelines 242, Renovering af bygninger med PCB, 1 Renoveringsproces (Renovating Buildings Containing PCBs, 1 Renovation Process)) (Andersen, 2013b).

If PCB-containing building materials are confirmed and the building is designated for renovation or demolition, the building owner has a duty to map the occurrence of PCBs pursuant to the provisions of the Statutory order on waste (Ministry of the Environment, 2012) (see Section 3, Surveys Prior to Renovation or Demolition).

If PCB-containing building materials to which building occupants have easy access are identified (e.g., caulk) they should be enclosed, as they may constitute a risk of exposure (see Section 1.3.2, Exposure Paths).

In the following section, different levels of PCB concentrations in indoor air are described relative to the recommended action values from the Danish Health Authority and the Danish WEA.

The recommended action values are often used as a measure for annual mean values. Determining annual mean values based on a single measurement or a few measurements of PCB concentrations is associated with uncertainty. German experts estimate that the uncertainty of determining annual average values based on a single measurement of airborne PCBs is 50 % for total PCBs of 300 ng/m³ (Danish Transport, Construction, and Housing Authority, 2015).

This means that a single measurement of a PCB concentration of between 200 ng/m³ and 600 ng/m³ could, in theory, indicate an annual mean value of 300 ng/m³. If an uncertainty of 30 % is considered for the Danish Health Authority’s higher recommended action limit, 3,000 ng/m³ will correspond to the interval 2,300–4,300 ng/m³. Table 23 lists the intervals for the two action values as well as for the interval 300-3,000 ng/m³.

Table 23. The Danish Health Authority’s recommended action values and the accompanying concentration intervals when the uncertainty is considered in relation to single measurements and annual mean value.

When assessing the measurements, it is important to ensure that they were done technically correct. However, the specific measurement conditions should also be considered. The measurement conditions during the actual measurement may have differed from those outlined initially. Temperature has a considerable effect on indoor-air PCB concentrations (see Section 1.6.3, Correlation Between Temperature and PCBs in Indoor Air) and it is necessary to ascertain whether the temperature remained within normal levels during the conditioning and measurement period. Furthermore, it is necessary to allow for seasonal changes and ventilation conditions.

Since measurements are usually taken in more than one location in a building, the two (or more) measurements should be compared with the recommended action values. It is not reasonable to take a mean value of the measurements, because PCB-concentrations may vary considerably within the same building (both in relation to the position of the measuring equipment and source types as well as to the airflows) (see Section 1.6, PCBs in Indoor Air).

The action values stipulated by the Danish WEA are based on those of the Danish Health Authority but are regarded as the PCB concentration present during working hours. The Danish WEA will only allow brief and occasional work to be carried out at levels close to 10,000 ng/m³ (Danish WEA, 2014).

If PCB concentrations below 200 ng/m³ are measured, the concentration is below the lower recommended action value stipulated by the Danish Health Authority when the 50 % uncertainty in relation to determining the annual mean value is allowed for.

If indoor-air PCB concentrations are below 200 ng/m³, but above a limit of detection (e.g., 30 ng/m³), there is very likely at least one PCB source in the building. Outdoor air measurements from Southern Sweden and near Birmingham in England showed PCB concentrations of a few ng/m³ (Backe et al., 2000; Curra & Harrad, 2000). It is likely that the measurements are affected by local sources if PCB concentrations in the indoor air exceed this level. Although it does not cause adverse health problems, in these cases one should decide whether a mapping of the building materials should be performed. This would help to identify PCB sources and enclose them to avoid dermal contact. Steps should also be taken to discover whether the source could be PCBs in a capacitor in a fluorescent light ballast, which should be removed to prevent the situation from worsening (see Section 5.2.4, PCBs in Capacitors).

If PCBs were confirmed in material samples, the accompanying documentation must be conveniently filed. The data are valuable for subsequent renovation or demolition projects where special consideration should be given to the working environment and waste (see SBi Guidelines 242, SBi Guidelines 242, Renovering af bygninger med PCB (Renovating Buildings Containing PCBs)) (Andersen, 2013b).

Occupants or building administrators should be familiarised with the way the ventilation system works and the fact that any changes could have a negative effect on the indoor climate (due to the presence of PCB sources in the building). Although the indoor climate is satisfactory, PCBs may have been confirmed in exterior caulked joints. It will be necessary to ensure that the ventilation system does not take in polluted air through the climate envelope (e.g., via leakages at windows with PCBs) (see SBi Guidelines 242, Renovering af bygninger med PCB, 1.7. Kontrol og dokumentation (Renovating Buildings Containing PCBs, 1.7 Control and Documentation)) (Andersen, 2013b).

PCBs may have been confirmed in material samples while PCB concentrations in the air do not give rise to intervention. If the preliminary investigation confirms the existence of substantial primary sources indoors (percentage content in caulk) while the air samples are low, consider whether the air measurements could be faulty and should be repeated.

If there is caulk or paint containing high-chlorinated PCBs (Aroclor 1260), the off-gassing to the indoor air will be limited due to the low vapour pressure of the heavily chlorinated PCBs (see Section 1.6.2, Correlation Between Indoor-Air Congener Type and Building Materials). This will not necessarily entail problems with the indoor climate, but caulk that is easily accessible should be enclosed.

In relation to the indoor climate, a concentration below 200 ng/m³ will not prompt a reaction from the Danish WEA. However, as above, an investigation to ascertain whether there could be PCB-containing capacitors in fluorescent light ballasts is recommended.

In theory, PCB concentrations measuring between 200 ng/m³ and 600 ng/m³ can be an expression of an annual mean value of 300 ng/m³, because the uncertainty associated with determining the annual mean value based on a single measurement is 50 % for a total PCB of 300 ng/m³. If the measurements were made for the purpose of an assessment relative to the Danish Health Authority's lower action value, several measurements should be made to determine whether the lower action limit has been exceeded.

If PCB concentrations of around or below 200 ng/m³ are confirmed repeatedly, it can be assumed that the concentrations are below the Danish Health Authority's lower action value.

If measurements indicate that concentrations are above 300 ng/m³, but below an annual mean value of 3,000 ng/m³, please consult the guidelines issued by the Danish Health Authority (see Section 1.3.5, Recommended Action Values). Initially, temporary intervention should be carried out (see Section 9.3, Temporary Abatement Interventions). If material samples have not already been collected, this must be done to identify the sources of PCBs in indoor air.

The recommended lower action value is set at 1,200 ng/m³ for indoor working environments. If measurements show values around this level, it might be necessary to make further measurements to clarify variation and the necessity to intervene.

If the measurements indicate values in the interval 1,200–3,000 ng/m³, the guidelines of the Danish WEA should be observed, which might involve an assessment of exposure levels relative to actual working time and the deadline for implementation of temporary and permanent abatement interventions (see Section 1.3.5, Recommended Action Values).

If PCB concentrations exceeding 4,300 ng/m³ are measured, the Danish Health Authority’s upper action value has been exceeded. Action without undue delay is recommended and the guidelines by the Danish Health Authority should be followed (see Section 1.3.5, Recommended Action Values). If PCB concentration are measured in the interval 2,300–4,300 ng/m³, further measurements are needed to determine whether the concentration is above or below 3,000 ng/m³.

If PCB concentrations in indoor air exceed the upper action value of 3,000 ng/m³, building occupants must be informed of the discovery of PCBs and be advised of the immediate abatement interventions implemented to mitigate PCB concentrations in the air (Danish WEA et al., 2011). In situations when it is difficult to mitigate PCB concentrations in indoor air within a reasonable time frame, the provisions in the Act on Urban Regeneration concerning condemnation can be applied (Ministry of Urban Areas, Housing and Rural Districts, 2013).

If considerable PCB concentrations in indoor air are confirmed without the primary sources having been identified, it is necessary to carry out mapping once more, as a source could possibly have been overlooked (e.g., hidden in the construction). In this scenario, one should consider whether the source may have been removed (e.g., the caulk could have been replaced or capacitors with PCBs in fluorescent light ballasts could have been replaced earlier).

A PCB concentration of 3,000 ng/m³ would also prompt action from The Danish WEA.

If PCB concentrations are in the interval 3,000–10,000 ng/m³, the guidelines issued by the Danish WEA should be observed, involving an assessment of exposure levels (relative to actual working hours) and a deadline for temporary and permanent remediation interventions (see Section 1.3.5, Recommended Action Values).

If concentrations exceed 10,000 ng/m³, an immediate enforcement notice will be issued (see Section 1.3.5, Recommended Action Values).

When a need to reduce PCB concentrations in indoor air has been identified, it is recommended to implement temporary abatement interventions according to the Danish Health Authority recommendations (2013a) and/or the Danish WEA (2014). Owners should consider whether the building should undergo more extensive remediation or be demolished.

In some cases, the temporary abatement will be adequate to meet the need for abating PCB concentrations in indoor air. However, if the PCB problem persists it will require ongoing follow-up over the next years to confirm that the desired effect will last into the future. Mapping results should be filed, as this documentation will be valuable in the context of later renovation or demolition projects (when PCB-containing materials require special management and waste separation).

Temporary abatement may consist of several interventions. At minimum, initial deep cleaning must be carried out, followed up by thorough cleaning on a current basis and increased rate of ventilation (www.pcb-guiden.dk). Furthermore, enclosure will ensure that direct dermal contact with PCB-containing caulk is avoided. Enclosure will also mean that dust will not come into contact with the caulk and that flaking from the caulk is avoided. This, in turn, will reduce the impact on the indoor-climate (see Section 1, PCBs – Properties and Applications).

Prior to implementing remediation intervention, it is necessary to be clear about how to avoid dispersing dust and dirt, as this may elevate PCB concentrations in indoor air.

Temporary abatement is intended to reduce exposure levels for building occupants. This remediation principle is discussed in SBi Guidelines 242 (SBi Guidelines 242, Renovering af bygninger med PCB, 2.1. Afhjælpningsprincipper (Renovation of Buildings Containing PCBs, 2.1 Remediation Principles)) (Andersen, 2013b). Remediation can also be enacted by reducing the source, thereby attempting to reduce indoor-air PCB concentrations.

A source could be enclosed by sealing it with aluminium foil and cover strips. Screening off for dust and flaking can be achieved by sealing the object with strong plastic, but this will not reduce the off-gassing of PCBs from the caulk to the same extent as aluminium foil (see SBi Guidelines 242, SBi Guidelines 242, Renovering af bygninger med PCB, 2 Afhjælpningsmetoder (Renovating Buildings Containing PCBs, 2 Remediation Methods)) (Andersen, 2013b).

The purpose of cleaning is to remove dust and particles in a room, as these will contain PCBs and could also increase source emission via contact (see Section 1, PCBs – Properties and Applications). One should start with a deep cleaning, using a vacuum cleaner with a HEPA filter. Thereafter, all surface areas should be cleaned with a wet or damp cloth or mop. Dusting with a duster or similar instrument should be avoided, as this will shift dust rather than removing it. Cleaning equipment that comes into contact with primary sources should be discarded and not used for further cleaning. A suitable protective suit and gloves should be used while cleaning and hands should be washed afterwards. Make sure that all cleaning equipment (mop, cloth, filters, water, suit) is discarded afterwards in accordance with applicable rules. Following this, regular cleaning should be performed with a wet or damp cloth and vacuum cleaning using a HEPA filter. Two weekly thorough cleaning sessions per week are recommended where all surface areas are wiped to reduce dust, however, there is no basis for recommending specific types of detergent (Haven & Langeland, 2011).

The combination of cleaning with an increased air exchange rate has been met with positive results (Haven & Langeland, 2011). Under the same conditions, increasing the air exchange rate will lower PCB concentrations in the indoor air, but will also increase the off-gassing from certain sources (see Section 1.6.4, Correlation Between Air Exchange and PCBs in Indoor Air). It is not entirely clear, therefore, to what extent an increased rate of air exchange will affect PCB concentrations in the indoor air (see SBi Guidelines 242, Renovering af bygninger med PCB, 2.7 Ventilation (Renovating Buildings Containing PCBs, 2.7 Ventilation)) (Andersen, 2013b). If there are PCBs in exterior caulk, care should be taken to ensure that air is not drawn in through the climate envelope by negative pressure ventilation, thus adding polluted air to the indoor air.

Airing out can be increased by doing so in a series of brief and strong bursts (e.g., making a through draft three times a day by opening windows and doors) which generally helps to improve the indoor climate.

If there is a ventilation system, it is necessary during the mapping procedure to investigate whether it has been contaminated internally by PCBs (see Section 8.8, Tertiary Contaminated Materials). If the ventilation system proves to be contaminated, the cause should be identified. It could be due to recirculation of contaminated air or it could be that the ventilation intake is close to a primary source. Once the cause has been identified, the source should be removed, and if possible the recirculated air should be filtered through a carbon filter. If necessary and possible, the air intake should be moved to a more appropriate location.

Following this, the ventilation system should be cleaned thoroughly on the inside. Any PVC flexible hoses in the system should be replaced. Vent ducts, fresh-air vents, and cavities should be included in the deep cleaning (see DS/EN 15780:2011) (Danish Standards, 2011; Haven & Langeland, 2011).

Building structures and airflows should be analysed and the ventilation should be correctly adjusted and balanced (see SBi Guidelines 242, Renovering af bygninger med PCB, 2.7 Ventilation (Renovating Buildings Containing PCBs, 2.7 Ventilation)) (Andersen, 2013b). Increasing the ventilation may cause draught or noise nuisance and each case should be assessed separately.

Instead of increasing the air exchange rate, the air can be cleaned by filtering it through a HEPA filter followed by an active carbon filter. Noise nuisance should be considered.

If a decision to screen off parts of the building is made (e.g., in the case of an extension containing PCBs) this might have to be ventilated via negative pressure ventilation to avoid PCB migrating to other parts of the building. Alternatively, dust-screening walls can be erected. If this measure proceeds for a long time (years), PCB-contaminated air must be prevented from penetrating the dust-screening wall and dispersing.

Under controlled conditions, increasing temperature will elevate PCB concentrations in the air, as increased off-gassing is proportional to a rise in temperature (see Section 1.6.3, Correlation Between Temperature and PCBs in Indoor Air and SBi Guidelines 242, Renovering af bygninger med PCB, 2.10 Temperatursænkning (Renovating Buildings Containing PCBs, 2.10 Lowering the Temperature)) (Andersen, 2013b). If the temperature can be kept low (e.g., via solar protection), heating and increased off-gassing can be prevented. With less heating or air conditioning, a general lowering of the temperature may possibly lead to decreased PCB emissions. However, the effect has not yet been robustly documented (Haven & Langeland, 2011).