Mastering Mold Problems
The basics of remediating a variety of fungal species in homes and other buildings
Unlike asbestos and lead, the permissible levels of mold are neither clearly defined nor strictly regulated. There are no definitive guidelines for what constitutes a mold-contaminated building, or for that matter, how to treat it. And while human response to mold varies widely, no official medical relationship exists between exposure and human response.
This spring, a nine-member expert committee for the National Academy of Sciences Institute of Medicine, found that damp, moldy buildings can make asthma worse and cause breathing problems in some people. However, there still is no definitive causal relationship established by the scientific community for the association between mold/moisture and other health complaints, such as fatigue, neuropsychiatric disorders, or other health problems.
Nevertheless, given how commonly moisture problems occur in homes and other buildings, people should remove any mold they find as soon as possible, the academy said. "It ... is a widespread problem that warrants action," the committee chairman noted. Indeed, when human health is at risk, failure to act can initiate tough Occupational Safety and Health Administration (OSHA) penalties (General Duty Clause) for the building owner. Environment professionals, as well as those responsible for the health and safety of a building's occupants, should educate themselves on this issue and what steps should be taken to identify and "treat" the problem.
Structural Problem May Be Present
First, it might be best to look at mold and conditions for its growth. Mold is a fungus that grows on damp or decaying organic matter. It can grow on window and door sills, walls, ceilings, and under nonporous wallpaper. Unpainted wood, sheetrock, carpet, and ceiling tile are rich in the nutrients needed for mold growth. Poorly designed and maintained heating, ventilation, and air conditioning (HVAC) duct systems can also support mold growth. When food, water, and a stable environment are present, mold can grow, with "water" in this case referring not only to standing water, but also to high relative humidity. A "stable environment" usually means no sunlight, limited airflow, and minimal or no disruption.
In a "healthy" building, the types and concentrations of fungal species found in indoor air should be identical to those present in the outdoor air. This indicates proper air circulation. When this balance is out of kilter, there is usually a system or structural problem with a building. It is likely to get worse if not treated. If one can identify the type of microbial organism(s) present, the source of the problem can often be determined. For example:
- Alternaria. -- HVAC system problems
- Stachybotrys chartarum -- water and rot conditions (very prevalent)
- Pencillium/Aspergillus (almost exactly alike) -- soil and wood rot
- Fusarium -- cellulose/water rot
The U.S. Environmental Protection Agency (EPA) maintains that "there is no practical way to eliminate all mold and mold spores in the indoor environment." Still, all experts agree that prior to any mold remediation activities, the source of the problem should be identified and repaired. So the best way to avoid the indoor air quality problems associated with mold is to prevent mold spores from growing in the first place. And because there are no conclusive studies that suggest which molds and what levels are harmful, EPA suggests a common-sense approach: "The way to control mold growth is to control moisture."
Therefore, the first step in remediation is to repair obvious leaks from roofs, windows, doors, and pipes. Chronic moisture buildup that is caused by poor ventilation or improper insulation should be eliminated. Building materials should be kept dry and adequately ventilated before and after installation. Some newer building materials, such as paperless wallboard, which have been specifically developed to resist mold growth, may be a good choice.
At present, there are no federal regulations for mold remediation methods, or certifications for professionals involved with the remediation process. However, several peer-reviewed and accepted guidelines exist that professionals responsible for building maintenance are now following:
- Mold Remediation in Schools and Commercial Buildings -- EPA
- Assessment & Remediation of Fungi in Indoor Environments -- New York City Department of Health
- Bioaerosols: Assessment & Control -- American Conference of Governmental Industrial Hygienists
- Standard and Reference Guide for Professional Mold Remediation S520 -- Institute of Inspection, Cleaning & Restoration Certification, standard cited by OSHA
- Assessment, Cleaning & Restoration for HVAC Systems/ACHR 2002 -- National Air Duct Cleaners Association
The first step of any mold remediation project is a thorough visual examination to determine the "order of magnitude" of the visibly contaminated materials. This also helps in the preparation of a remedial work plan. Not always visible, mold can occur behind walls and other hidden places in a building envelope. This may necessitate looking under floor boards, behind wallpaper, in basements, etc. The interior of the HVAC system should also be inspected.
If visible mold is present, this examination may be sufficient. However, if no one is sure what is causing the mold contamination, sampling should be considered as part of the site evaluation before remediation. Sampling may help locate the source of the mold contamination; it will identify some of the mold species present, and it will differentiate between mold and soot or dirt.
Four Different Methods
If mold growth is determined to be localized and accessible, it may be possible to eliminate the moisture and clean up the mold during routine maintenance and cleaning. However, if it is not certain what is causing the mold (multiple factors may be at work) or if the mold infestation is pervasive and not easily visible, it is time to contact a qualified remediation contractor. Qualified contractors will be able to present documentation of ongoing training, long years of experience in mold remediation, and references. (See Contractor Checklist).
Whether the work is completed by in-house personnel or an outside contractor, one or all of the four methods listed below will be used to remove the mold. These four recommendations are based on type of materials and area to be cleaned.
- Wet Vacuum -- Wet vacuuming is recommended for both porous and nonporous hard surfaces (not wallboard) that are still wet. Wet vacuuming will leave some mold spores in porous surfaces, but the spores will not grow if the material is thoroughly dried. The tanks, hoses, and attachments of wet vacuums should be thoroughly rinsed and dried after use.
- Damp Wipe -- Mold can generally be removed from nonporous surfaces by wiping or scrubbing with water or water and detergent. Wood cleaner can be used on wood surfaces. To discourage further mold growth, surfaces should be dried quickly.
- Discard -- Mold can destroy porous materials. Contaminated, unsalvageable building materials should be double-bagged and sealed in 6-mil poly sheeting. To minimize the dispersion of mold spores throughout the building, the material should be bagged before removing it from the containment area. Generally, these contaminated building materials can be treated as normal waste.
- HEPA Vacuum -- EPA recommends high efficiency particulate air (HEPA) vacuums for the final cleanup of remediation areas after everything has been thoroughly dried. Dust that has settled on surfaces outside the remediation area should also be HEPA vacuumed. Before vacuuming, all contaminated materials should be removed. After vacuuming, the filter and contents of the vacuum should be sealed in a plastic bag.
Protecting the Public and Remediators
Some of the engineering controls that contractors use to secure the environment and protect the building occupants and workers doing the cleanup are very similar to those used in the asbestos abatement industry. This is because mold spores (like asbestos fibers) can travel on air currents and can quickly spread to other areas of a building.
HEPA equipped air filtration devices (AFDs) filter the air in the contaminated areas and help establish negative air pressure. Polyethylene sheeting on walls, ceilings, and floors will contain the work area and decrease the likelihood of airborne mold spores traveling to "clean" areas. Blocking supply and return HVAC vents also prevents the migration of airborne spores. Air-locks and decontamination chambers prevent mold spores from traveling to "clean" areas as remediators leave contaminated sites.
Evidence suggests that the level of exposure affects the harmful effects of mold, so EPA guidelines for personal protective equipment (PPE) should be followed.
Because there are no scientific data to support an acceptable level of exposure to mold, there are no current EPA or OSHA standards to indicate when cleanup and mold remediation has been successful. EPA guidelines indicate that sampling is not required. However, EPA does recommend evaluating the cleanup against the following criteria:
- The water or moisture problem must be completely fixed.
- Mold removal must be complete, with no visible mold, mold-damaged materials, nor mold odors present.
- If the site is sampled, the kinds and concentrations of mold and mold spores should be similar to those found outside.
- The site should be revisited, and it should show no signs of water damage or mold growth.
- People occupying or re-occupying the space should express no physical symptoms or health complaints.
As state and federal regulators increase their attention to the areas of mold and "sick" buildings, more legislation is bound to come. Eventually, there will be certification requirements for mold remediators, and national and state standards governing the mold remediation processes will be issued. In the meantime, the most practical approach is to adhere to current industry and EPA guidelines; communicate regularly with building owners and occupants; document recommendations, the remediation process, and progress; and select only qualified and experienced remediation contractors.
Environmental professionals and building owners and managers should strongly consider the following contractor qualifications when selecting a mold remediation contractor:
- Current pollution liability insurance that covers all pollutants, with no exclusion for "microbial matters"
- Demonstrated experience/expertise in mold/microbial remediation
- Resumes of key project personnel demonstrating investment in this evolving industry by participating in various training courses and earning industry-recognized certifications, from organizations such as the Indoor Air Quality Association, National Air Duct Cleaners Association, or American Indoor Air Quality Council
- Proof of written work practices and procedures specifically for microbial remediation
- Demonstrated expertise in the effective operation of HEPA-filtered equipment, including a written equipment operation program and written integrity testing program for HEPA equipment
- Documentation of OSHA mandated safety programs i.e., respiratory protection programs, medical surveillance programs, fit test programs, etc.
This article originally appeared in the 05/01/2005 issue of Environmental Protection.