Fungal Contamination in Public Buildings: Health Effects and Investigation Methods

3. Investigation of Fungal Contamination of the Non-Industrial Workplace (Continued)

3.2 General Principles

Indoor air quality investigations⁴ can begin in several ways. Some building owners or managers conduct regular air quality audits to detect problems before they can potentially affect occupants. At the other end of the spectrum are investigations which occur as a result of acute reactions from individuals entering a building. Appropriate measures should be taken when an investigation is prompted by health complaints. It is important to involve specialists with recognized professional training and experience to investigate potential mold problems in public buildings using methods documented by the ACGIH (1999) and the American Industrial Hygiene Association, or AIHA (Dillon et al. 1996).

In HVAC systems, humidifiers, dirty filters and accumulated debris in ducts subject to condensation or leaks can all be sources of building-associated mold. Spores can be blown out of ducts in a periodic fashion. Fungi can be released when occupied spaces adjacent to contaminated wall cavities, elevator shafts or faulty sewer drains are depressurized. Release from these sources can be affected by air infiltration rates and pressure differentials resulting from wind and thermal loading (weather) and unbalanced ventilation or exhaust systems. Distribution of fungi from carpets or surface contamination is affected by activity in the occupied space and the intensity of cleaning.

If required, laboratory tests must be done using appropriate methods and by qualified and experienced professionals. Commercial laboratories should demonstrate successful performance in the AIHA Environmental Microbiology Proficiency Analytical Testing (EMPAT) program and preferably be an Environmental Laboratory accredited by the Standards Council of Canada (SCC),⁵ or ISO or Good Laboratory Practice (GLP) certification.⁶

There are also university and governmental laboratories with highly qualified specialists in mold identification that can provide reliable data; however, they must be required to use recognized methods. Canada Mortgage and Housing Corporation (CMHC) attempts to maintain a list of laboratories that have provided services for the Government of Canada. Provincial officials in Health or Labour Departments may also be able to provide recommendations. All reasonable steps must be taken to ensure that no action during the investigation or remediation⁷ process results in further contamination of the building or increased risk for occupants or the public. Finally, the provision of reliable and timely information to occupants is a critical aspect of any IAQ investigation because of the need for individuals in one of the potential risk groups to be informed in the event of a microbiological problem in their workplace or education facility.

3.3 Objectives of a Mold Investigation

As noted above, the intensity and complexity of mold investigations vary according to the size and nature of the building, whether an air quality audit is being conducted or whether the investigation is a response to a health complaint. The benchmark is the CEOH (CEOH 1989, 1995a, 1995b) advice to minimize exposure to fungi, that there are population health effects of mold and dampness and that there are risk groups. The goals are to define and manage the microbial problem(s) and return the building to a satisfactory level of performance. Air quality investigations for audit purposes are not considered here.

The following discussion refers to an incident in which a health complaint has been made and initial evidence shows that mold might be one of the potential issues.

The goals of such investigations are to:

• establish the cause, nature and extent of fungal contamination;
• assess the risk of adverse effects on the health of occupants;
• manage the microbial problem(s); and
• return the building to a satisfactory level of performance.

Factors to consider when addressing a potential mold problem

1. It is important to focus on the problem as quickly as possible to allow the investigating team to provide clear answers to the occupants, managers and health providers about the state of the building. For reasons discussed in section 3.4, mold problems very often result from chronic moisture problems. If exposure has reached the point where health complaints have been made, it has typically taken years for this to occur. Since there is some mold on materials in all buildings, determinations must be made regarding the nature and extent of the contamination and who is exposed.
   
   
2. The first step in a mold investigation is an informed inspection during or after which air samples may be taken (see 3.4.1). Investigators must decide whether there is a possible hidden contamination, including in the HVAC system or wall cavities (Miller 1993). In such cases, air samples are especially useful. Air samples collected using methods that require the culturing of viable spores are often sensitive even to subtle problems, and provide results after 7 to 10 days. In contrast, non-viable (sticky surface) samples are generally less sensitive, but provide data within 24 to 48 hours. All samples should be taken according to the methods described in the AIHA Field Guide (Dillon et al. 1996).
   
   
3. After air samples are taken, floors and other surfaces where dust may accumulate should be cleaned with a high efficiency particle arresting (HEPA) vacuum. With few exceptions, most exposure to mold spores arises from people around in the occupied space which stirs up settled dusts. Cleaning will, in most cases, immediately reduce exposure while the investigation process continues. If there are people in the building, the decision of whether or not to take air samples should be made quickly so cleaning can proceed.
   
   
4. As the nature and extent of the contamination become known, this information needs to be given to occupants. Among other things, this permits those with special sensitivities to unusual airborne mold exposures to consult with a medical professional about whether they should remain in the building, or not.
   
   
5. An accurate survey of the extent of the contamination and moisture or damage is required to document and remediate the affected area. There are three purposes for this important step: (a) the complexity of the removal process depends on the affected area (ACGIH 1999; New York City Department of Health 2000); (b) there is evidence that the potential for health effects among occupants depends on the area of mold contamination; and (c) the quality assurance process for the remediation depends in part on the thoroughness of the investigation (AIHA 2001). During the investigation stage, dust control (e.g. misting and using a HEPA vacuum) is required when making small investigative openings in walls (< 0.1 m2) adjacent to occupied space. Larger inspection holes, especially where mold contamination has been determined to be extensive, requires containment or other protective measures if the space is to be re-occupied before doing repairs. The survey should also assess the degree of connection of the discovered mold to the living/working space. The documentation step can be eliminated if the building has been unoccupied.
   
   
6. In documenting the nature and extent of the mold observed, there are several reasons for determining the fungal species present. The first reason is to verify that the damage seen is really fungal in nature. Sometimes dirt or other deposits on surfaces in buildings or HVAC diffusers are not building-associated mold. It can also be useful to know what environmental conditions have led to mold growth. The species of mold present can provide valuable clues. Molds that grow under damp conditions are different from those that grow under very wet conditions. This might help in identifying sources of water that might not be obvious. For example, the finding of a wet-loving building- associated mold near a window frame might suggest a significant leak around the window or a condensation problem in the wall cavity. The finding of a damp loving mold behind a chest of drawers on an outside wall might suggest inadequate ventilation or insulation. In addition, the occupants' medical professional may find it useful to have a list of the dominant fungi present.
   
   
7. Fungal damage should be quickly remediated using the protocols outlined in the New York City Department of Health Guidelines (2000) and ACGIH guidelines (1999; Chapter 15) (ACGIH 1999; New York City Department of Health 2000) and quality assurance process used (AIHA 2001). These are similar to those outlined in the CEOH Guide (1995a). Note that the primary method to assure that mold remediation has been done properly is confirmation that the causal water or moisture sources have been identified and eliminated. Repairing mold damage in an exterior wall where it has been determined that there is a good air barrier can typically be done without additional protective measures. The air barrier should normally be sufficient to prevent the ingress of mold spores indoors. It is important to note, however, that construction, demolition and repairs all result in the release of construction dusts and other debris. It is generally not appropriate to permit the space to be occupied when construction is actively under way. Measures to protect contents from settled dusts during repairs, plus HEPA cleaning after repairs, are additional steps potentially required for re-occupancy, depending on the nature and extent of the damage and repairs. Containment of dust and spores using negative pressure and isolation of the remediation area is a prudent practice. There is no public health reason to contain the outside of a building in the situation where remediation is being done from the exterior. A possible exception is when the exterior walls are in a semi-enclosed space (e.g. a stairwell).
   
   
8. The risk of health consequences from mold exposures arising from mold-damaged building materials varies with the degree of isolation from the occupied space. Considering construction methods and climates in Canada, exposure risk from greatest to least would be growth: (a) on surfaces exposed to occupied space; (b) on interior walls or floor cavities (especially if there are ducts); (c) in exterior walls with poor air barriers; (d) in exterior walls outboard of a good air barrier; and (e) in attic space or roof space above an air barrier. If the mold damage is in the ventilation system, immediate steps are required to stop the spread of contamination. If the contamination is on the surface of walls, ceilings or floors exposed to the occupied space, immediate steps are required to contain the mold-damaged areas. Options to consider are the use of polyethylene barriers either with or without depressurization. If the contamination is mainly in demising wall cavities, access to highly damaged areas of the building should be restricted until remediation is complete. In the remaining areas, professional judgment will have to be made on the potential to introduce contamination into the occupied spaces until repairs are complete. Additional steps to consider include regular HEPA cleaning with some air monitoring to ensure the effectiveness of the cleaning. A team to manage the remediation and repair process needs to be created. The remediation and repair work should be closely monitored to ensure its effectiveness, and quality assurance and compliance testing should be incorporated.
   
   
9. Typically, all porous materials on which there has been fungal growth must be safely and effectively removed, followed by a thorough particulate cleaning by crews appropriately trained in dust control. Surfaces that collect large amounts of settled dusts and spores, including carpets and ceiling tiles, may also need to be removed. These are difficult to clean and there are no accepted methods of verifying that they have been adequately cleaned. Factors to consider in making the decision to remove remaining porous surfaces in mold-damaged areas include the nature, extent and duration of the mold problem in the building. As remediation proceeds, exposed areas must be checked for any remaining mold damage revealed during demolition. Semi-porous materials on which mold growth has occurred can be cleaned if they are structurally sound, and must be replaced if they are not. Dusts on non-porous surfaces can usually be cleaned using methods appropriate for the given material.
   
   If the contamination was extensive (i.e. on the upper end of the remediation categories defined by ACGIH [1999] or New York City Department of Health [2000]), settled dust samples should be collected after remediation. The purpose of this step is to provide documentation that the affected areas have been thoroughly cleaned. The dry weight of settled dust collected/m² should be measured according to the guidance from the AIHA (2001). When the mold- damaged materials have been removed and the affected area thoroughly cleaned with a HEPA vacuum,⁸ the building can be treated like a normal construction site for the build-back.
   
   After the repairs have been completed, air samples taken one or two weeks after the ventilation system has been running normally can be useful as a last measure of the success of the steps taken.

^4. In section 3, "investigation" means the process of appropriately trained individuals entering the building to conduct inspection, sampling, documentation and production of reports.

^5. The Standards Council of Canada (SCC) offers environmental laboratory accreditation in partnership with the Canadian Association for Environmental Analytical Laboratories (Inc.) (CAEAL). CAEAL is a not-for-profit association of public and private sector laboratories.

^6. Good Laboratory Practice (GLP) refers to compliance with a series of guidelines, developed by the Organisation for Economic Co-Operation and Development (OCED), regarding laboratory facilities, standard operating procedures (SOPs), quality assurance and reporting. GLP certication is granted by a number of agencies around the world, including the US Food and Drug Administration.

^7. "Remediation" includes both the thorough cleaning of any mold growing in the building and correcting the building defect that led to mold growth (excessive humidity, water leaking, or water infiltration from the outside).

^8. Residual dust should be reduced to as low as can reasonably be achieved. This has been defined as less than 100 mg dry weight/m² on smooth surfaces in a number of cognizant authority documents (ACGIH 1999; AIHA 2001).