Mould Assessment and Remediation
In recent years, attention has become increasingly focused on the very real issues associated with adverse impacts on indoor air quality and health risks resulting from exposure to moulds in the built environment. Moulds are ubiquitous, and mould spores are a common component of household and workplace dust. However, when mould spores are present in abnormally high quantities, they can pose an increased health risk to humans. Moulds cause adverse human health effects through three specific mechanisms: (i) immune responses / allergic reactions, (ii) direct fungal infections, or (iii) through the production and subsequent exposure to mycotoxins.
Mycotoxins are toxic metabolites excreted by some moulds under specific environmental conditions. Some mycotoxins are harmful to humans and animals at sufficiently high exposures. Mycotoxins can be found on mould spores, mould fragments, and the substrate upon which the mould grows. The routes for exposure to mycotoxins include ingestion, dermal exposure and inhalation. Under optimal environmental conditions, moulds proliferate into colonies and mycotoxin levels can increase. The adverse health effects depend upon the type and amount of mould present, mycotoxin concentrations, the duration of exposure and the sensitivity / susceptibility of the exposed individual.
Moulds are incredibly resilient and adaptable. Moulds obtain the nutrients they need to proliferate through the decomposition of organic matter. Most moulds found in the indoor environment obtain nutrients from dead moist organic matter such as wood, paper, paint, fabric, plant soil and dust. In short, all that moulds need to proliferate is a readily available food source, adequate moisture, and time.
Buildings often incorporate a large number of hidden and poorly ventilated cavities. In the presence of adequate moisture, these cavities provide ideal environmental conditions for the proliferation of moulds. Floods, leaking pipes, leaks in the building envelope are all potential sources of water ingress resulting in moisture and relative humidity levels that can lead to mould infestation. Increased ambient humidity as a result of inadequate ventilation or improper drying of flooded areas can also lead to mould growth. Mould spores can remain viable for many years in a dormant state, requiring only adequate moisture and nutrient for mould growth to proliferate.
As common building materials are capable of sustaining mould growth, and mould spores are ubiquitous, mould growth in an indoor environment is typically dependent on the availability of moisture. Therefore, the key to preventing mould growth in the indoor environment is eliminating the environmental conditions that promote proliferation, the most important of which is to remove the source of moisture. Repairing leaks, improving ventilation, reducing indoor air humidity, and proper clean-up after flooding episodes, are key strategies to preventing mould infestation. However, once mould infestation has occurred, immediate corrective actions and remediation are required to minimise further damage and potential risks to health.
We have developed an integrated and comprehensive approach to the assessment and remediation of mould contamination using a three stage process based on the Australian Mould Guideline AMG-2005-1.
1. Detailed Site Assessment 2. Remedial Action Plan 3. Remediation and Validation
Stage 1 Detailed Site Assessment
A detailed assessment is conducted by trained personnel to identify common indicators of mould infestation and identify the cause/source of the moisture and mould growth.Â Such an investigation includes:
- Inspection of the general and concealed areas (including roof cavities, sub-floor areas and wall cavities) of the structures for visible evidence of mould contamination, poorly ventilated areas and water leaks/ingress.
- Visual inspection and sampling of concealed areas are conducted by a borescope fitted to a digital camera, and further destructive investigation and sampling can be conducted as required i.e. aerocell wall cavity sampling
- Moisture testing of substrates to identify damp or problematic areas and suitable environmental conditions for mould growth using a protimeter.
- Air and surface samples are collected to categorise the mould species present and to establish the level of contamination.
- Review the need to establish health surveillance for the affected people.
Stage 2 Remedial Action Plan
The remedial action plan (RAP) will utilise the findings of the detailed assessment to determine the most suitable method for decontamination and validation of the site. The RAP will:
- Specify the methodology for the remediation of the subject buildings / structures and minimise the risk of cross-contamination and recontamination.
- Specify requirement for repairs or upgrade of structures to prevent moisture build-up or ingress of water.
- Specify procedures for drying-out the subject buildings / structures and contents.
- Specify the PPE requirements for personnel conducting the remediation works.
- Specify the engineering controls and decontamination facilities and procedures for the remediation process.
- Specify the environmental safeguards to be implemented during the remediation works.
- Establish remediation goals and validation criteria for the remediation works.
Stage 3 Remediation and Validation
We can assist with the selection of a suitable contractor to conduct the remediation works and Project Manage the remediation works.
During and following remediation works, the validation sampling programme outlined in the RAP will be implemented to ensure that the remediation objectives specified in the RAP have been achieved. The validation study will assess the results of the post-remediation testing against the clean-up criteria stated in the RAP.
The clean-up and validation standards will be based on the latest Australian Mould Guidelines (AMG-2005-2).
- For airborne fungi, a rating guide will be used for total (viable and non viable) fungi counts, expressed as indoor concentrations in spores/m3 of air sampled.
- For surface fungi, a rating guide will also be used for total (viable and non viable) fungi counts, expressed as fungal spore concentration in spore counts/cm² of area sampled.
During remediation, dehumidifiers are used in conjunction with an air scrubber to isolate the room (preventing the ingress of contaminated air), dry the area and remove airborne spores. It is important to stage the works to avoid cross contamination from adjacent pressurised containment areas. Relative humidity is monitored during remediation, which, in addition to the airborne and surface mould tests mentioned above, will ensure the affected surfaces (e.g. walls) are sufficiently dry for clearance purposes.