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Guidelines Part 4
Guidelines Part 4 - Indoor air quality
G4.79 Moulds and indoor air quality
Issued June 14, 2002; Revised February 8, 2007
Regulatory excerpt
Section 4.79(1) of the OHS Regulation ("Regulation") states in part:
The employer must ensure that the indoor air quality is investigated when
(a) complaints are reported ...
Section 4.79(2) states in part:
An air quality investigation must include ...
(c) sampling for airborne contaminants suspected to be present in concentrations associated with the reported complaints ...
Section 3.10 states:
Whenever a person observes what appears to be an unsafe or harmful condition or act the person must report it as soon as possible to a supervisor or to the employer, and the person receiving the report must investigate the reported unsafe condition or act and must ensure that any necessary corrective action is taken without delay.
Purpose of guideline
This guideline discusses the application of the Regulation to workplaces with mould showing on exposed or hidden surfaces, or where mould may be a factor in complaints regarding indoor air quality. The guideline provides information for investigating indoor air quality complaints with respect to mould contamination, including information on sampling for the presence of moulds in buildings. Information is also provided on possible health effects and for cleanup personnel involved in the remediation of buildings damaged by water and mould.
The presence of mould should be suspected if there is visible moisture (condensation) on building surfaces or if there has been water damage, for example, due to roof or wall leaks, plumbing failures, or flooding. Workers who occupy damp or water-damaged buildings and workers involved in the remediation of water-damaged buildings may be exposed to mould. The presence of moulds may also result in complaints from workers about poor air quality in the building, such as a musty odour. These complaints require an investigation by the employer (Regulation sections 3.10 and 4.79(1)). In order to establish whether there is a potential for worker exposure to mould, a risk assessment must be carried out. Some basic principles are outlined in this guideline, including precautionary measures that need to be considered in order to minimize the potential for worker exposure.
Note: Public exposure to moulds. WorkSafeBC applies the Regulation to protect workers under its jurisdiction from the adverse health effects of exposure to moulds. While public exposure is not within its jurisdiction, WorkSafeBC cooperates with other agencies, such as public health authorities and the Canada Mortgage and Housing Corporation, in finding solutions to the problems of mould contamination.
Conditions for mould growth
Moulds are part of the fungi kingdom and serve an important role in breaking down organic matter. They are found both outdoors and indoors. Fungi can form a colony, which is a visible mass of interwoven filaments that may appear cottony, velvety, granular, or leathery. Fungi can be any colour but usually will appear as a shade of white, grey, brown, yellow, or green. The fungi most commonly found growing indoors are often called "moulds" (for example, species of Penicillium, Aspergillus, and Cladosporium). For the purposes of this guideline, the terms "mould," "mildew," and "fungus or fungi" are interchangeable.
Moulds spread naturally through the release of spores into the air. Any air movement will cause the dry spores to be carried with the air current; eventually the spores will land on a surface. Moulds may also spread through direct mechanical transfer of mould-covered materials, or by a person or animal brushing against a mould and then depositing some mould on another surface. Once a colony of mould is established and subsequently disturbed or damaged, spores may become airborne and spread throughout the building.
As long as moisture and nutrients are present, mould growth will usually continue unabated. Moulds are likely to grow where there is water or prolonged dampness - such as in bathrooms, basements, water-damaged walls, ceiling/roofing material, and the damp parts of refrigeration or air conditioning systems (for example, air chillers or drip trays). A source of nutrients for mould is basically any organic material and can include simple sugars and starches as well as more complex carbon-containing substances such as paper and wood. Many porous building materials such as drywall, wallboard, wallpaper, insulation, ceiling tile, and wood contain organic material.
Without moisture, mould cannot grow or reproduce and will die or enter a dormant stage. In the case of some moulds, this dormant stage can last for years. However, given the right conditions, such as a water or moisture supply, the mould can become active (start growing again) and release spores.
Health effects of exposure to moulds
A person's exposure to moulds is primarily through inhalation of airborne spores. For most people, exposure to mould does not result in any significant health effects. Most of the health complaints reported are upper respiratory in nature, such as coughing, itchy eyes, stuffy nose, sneezing, and sore throat. However, mould exposure in water-damaged buildings has also been linked to the development of asthma in both children and adults.
For a person who has a compromised or sensitized immune system, health effects can be severe. Some moulds are infectious (pathogenic) and others produce chemical by-products or mycotoxins (toxigenic agents). For those individuals with compromised or sensitized immune systems, exposure to pathogenic moulds or their toxic by-products may be associated with a variety of adverse health effects, including allergic reactions, asthma, pneumonitis with flu-like symptoms, infections of the upper airways, sinusitis, or other lung diseases.
Section 4.79 requires an investigation of a worker's complaint related to indoor air quality. However, there are currently no exposure limits or standardized risk assessment procedures to accurately predict a worker's health risk from mould exposure. Nor is there at present a standardized protocol for sampling of these organisms, although a number of methods are currently used.
Investigation of mould contamination
The extent of mould contamination can be determined in two ways. The primary method is through a visual assessment to establish the presence of mould and the extent (area) of growth. This could include an intrusive investigation for the presence of hidden mould.
The secondary method is via air sampling to establish the presence and types of mould spores in the air. Trained individuals are required to identify the presence of specific types of mould and to carry out representative sampling. Also, microscopic identification of the spores and mould colonies requires considerable expertise, and these services are not routinely available from commercial laboratories. For someone with limited experience, sampling results are difficult to interpret. Experience in interpretation of results is essential.
Visual assessment
The presence and extent of visible growth of mould can be checked by direct observation and measuring the area of coverage. It may be necessary to cut access holes or use equipment such as a borescope (an instrument that uses optical fibres for the visual inspection of hard to reach spaces) to view spaces in ventilation ductwork or inside wall cavities to check for hidden sources of mould and the extent of water damage. Once the area of mould coverage has been determined, Table 1 can be used to categorize the problem and determine the level of controls recommended to control spores and mould dispersion.
Note: Any disturbance of a mould source, for sampling, should not be conducted without taking some precautions. The precautions listed under "Small" in Table 1 should be adequate.
Section 4.78(2) of the Regulation requires regular inspection of ventilation systems for conditions that could promote the growth of micro-organisms - conditions such as water leaks and stagnant water pools - along with correction of any deficiencies found. This action is required whether or not there are reports or complaints regarding indoor air quality.
Bulk or surface sampling
If it is necessary to determine the type of mould, a small sample can be taken by scraping some visible mould material or cutting a piece of material (such as mould-stained drywall) with a clean tool and placing the sample into a sample vial or sealable plastic bag. Another method is by applying a piece of clear, not semi-transparent, 18 mm (3/4 inch) cellophane tape against a contaminated surface and sticking the tape to a standard glass 25 x 76 mm (1 x 3 inch) slide or to a piece of plastic for further identification.
Air sampling
Is air sampling for mould needed? In most cases, if visible mould growth is evident, sampling for airborne fungal material is not necessary. In specific instances, such as where the source(s) of the mould contamination is unclear or health concerns are a problem, air sampling may be considered as part of the site investigation. Keep in mind that air sampling for mould provides information only for the moment in time in which the sampling occurred, much like a snapshot. Furthermore, reliable sampling for mould can be expensive, and generally accepted standards for judging what is and what is not an acceptable or tolerable quantity of airborne mould spores have not been established.
In limited circumstances, air sampling for mould in indoor environments before and after remediation can be used as an indicator of remediation effectiveness. To be effectively used in this manner, the mould makeup of the outdoor air should also be determined so that a side-by-side comparison can be made in terms of mould types present and their relative numbers indoors versus outdoors. Post-remediation air sampling should be conducted using a non-culturable sampling method (for example, spore trap sampling or PCR sampling), as the mould may have been killed during the cleaning process. Remember, dead mould can still have allergenic or toxic properties!
Prevention and remediation of mould contamination
Moisture is an essential condition for mould growth. A primary objective in all mould remediation is to identify the sources or causes of moisture and eliminate or control them. Evidence suggests that flooding for periods as brief as 48 hours can lead to mould problems. Other possible sources of moisture are condensation and building leaks.
Once moisture is brought under control, remediation activities can commence. Table 1 provides guidance on methods of remediation and the recommended personal protective equipment. These control measures are based on methods developed by the American Conference of Governmental Industrial Hygienists (ACGIH) and the "EPA Protocol" (Mold Remediation in Schools and Commercial Buildings issued by the United States Environmental Protection Agency, March 2001). The EPA document can be viewed at http://www.epa.gov/mold/mold_remediation.html.
The person responsible for remediation will need to use professional judgment and experience to adapt the guidelines in Table 1 to specific projects. In cases where a particular toxic mould species has been identified or is suspected, when extensive hidden mould is expected (such as behind vinyl wallpaper or in a ventilation system), or when the chances of the mould becoming airborne are estimated to be high, a more cautious or conservative approach to remediation should be considered. A health and safety professional with training and experience in conducting mould investigations and developing safe work procedures should be consulted in these circumstances.
Remediation workers need to know the possible health effects of mould exposure to be able to recognize and report symptoms. The emphasis is exposure avoidance through control measures and work procedures. Ventilation, personal protective equipment, and personal hygiene all contribute to safe work methods.
Table 1: Guide for Removing Visible Mould Growth in the Indoor Environment
| Extent of Visible and Hidden Mould Growth (surface area) | Minimum Recommended PPE1 | Control Measures to Prevent Dust or Spore Dispersion2 |
|---|---|---|
| Small Total surface area affected is less than 1 square metre (10 square feet) |
N95 respirator or half facepiece respirator with HEPA filters, gloves, and goggles. | Isolation of the work area; wet wiping or misting of surfaces with water containing a surfactant (wetting agent); and the use of drop sheets to prevent dispersion of dust and spores. Material is removed with minimum of dust and spore dispersal and placed in a plastic bag and sealed. |
| Medium Total surface area affected is between 1 square metre and 10 square metres (10 square feet to 100 square feet) |
N95 respirator or half facepiece respirator with HEPA filters, gloves, disposable coveralls, and goggles. | Limited containment: use polyethylene sheeting ceiling to floor around the affected area with a slit entry and covering flap. Maintain area under negative pressure with HEPA filtered negative air unit. Block supply and return air vents within the containment area. |
| Large Total surface area is greater than 10 square metres (100 square feet) or the potential for increased occupant or remediator exposure during remediation is estimated to be significant. |
Full facepiece or powered air purifying respirator (PAPR) with HEPA filters, gloves, disposable coveralls (covering head and boots), and goggles. | Full containment: use of critical barriers. Maintain area under negative pressure with HEPA filtered fan unit exhausted outside the building. Block supply and return air vents within the containment area. Provide facilities and procedures for decontamination and personal hygiene. |
For outdoor remediation projects where mould infestation has not breached the inner vapour barrier, the guidelines in Table 1 apply without the requirement for containment when there is good natural ventilation to the outdoors. Note that for situations where the "Extent of Visible and Hidden Mould Growth" is categorized as "Large" openings and intakes into a building should be effectively sealed to prevent mould contamination from remediation activities entering the building. By using the "Extent of Visible and Hidden Mould Growth" criterion, the appropriate Personal Protective Equipment (PPE) for outdoor remediation work can still be determined.
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