Learning from Stachybotrys Chartarum: How to Find Hidden Mold in Buildings

Claude Mainville, p.senior eng., Marie-France Pinard, Ph.D., Louis Gagnon, M. Sc., Robert Kelly, B. Sp., Alain Beaudet, jr eng.
See also: 5th International Bioaerosol Conference

1 — Summary

An open and multidisciplinary approach is needed to make a complete, fast and efficient diagnosis of hidden mold problems in buildings. A typical case study involving a Stachybotrys chartarum contaminated buiding will be used to illustrate the many critically important steps that are required to make your diagnosis a success story. This four story office building, located in Montréal (Québec) experienced extensive water damage from the 1998 ice storm. After partial evacuation prompted by health officials, numerous remaining occcupants complained of respiratory and other symptoms.

Visual inspection of the premisses and their ventilation showed extensive water infiltrations from the roof top ventilation units and from the lower part of the exterior walls. This abnormal water activity caused fungal contamination with Stachybotrys chartarum and Ulocaldium on surfaces with a total visible surface of around 1.5 square meters. Deposited dust in carpets, wall board and ventilation units was heavily contaminated with millions of cfus per gram of Gram positive bacteria, yeasts and Trichoderma viride.

Remaining occupants left the building and their symptoms were either alleviated or disappeared completely.

Remediation was done according to the New York Department of Health protocol for Stachybotrys chartarum contamination. Upon opening of wet walls, an additional surface of 10 square meters was found with heavy Stachybotrys chartarum mold contamination. This finding shows that the vast majority of moldy surfaces was hidden and would not have been visible without opening the structure.

2 — Introduction : the mold paradigm: between " too much " and " not enough "

In the field of mold control in buildings, every step forward is the catalyst for renewed controversy.... and headaches for consultants. What is " not enough " in the eyes of certain people is already " too much " in the eyes of others.

In fact, this situation is not surprising: in the last thirty years, there has been a major change in our way of life. After the energy crisis, a growing concern about keeping energy costs as low as possible gave rise to a new generation of houses and buildings, with minimal fresh air intake and maximal thermal insulation. In parallel, numerous unprecedented waves of budget cutbacks decreased the quality level of maintenance in buildings. In consequence, mold contamination problems due to uncontrolled water activity in buildings and in HVAC system, especially those with porous duct insulation, are now more and more frequent in these " air tight " but " water leaky " constructions.

Public Works and Government Services Canada, after investigating 95 office buildings between 1987 and 1994, have discovered that, in 21 % of these buildings, microbial contamination was the major contributing factor to the low quality of indoor air.

In addition to microbial contamination in buildings, the overall load of pollutants is rising in water, soil and air. The presence of chemicals is unavoidable in every aspect of our everyday life: food additives, pesticides and drugs, etc... This situation has certainly contributed to the sharp rise in allergies and hypersensitivity problems in our population. People are therefore more sensitive than before to mold contamination in their indoor environment.

For all these reasons, and in that context, it is misleading to refer to Stachybotrys chartarum, or other mold contaminants in buildings, as " an old problem that is now given exaggerated attention ". Mold is ubiquitous, and has been for millions of years, but its impact in indoor environment is now much greater than it ever was. As building consultants for many years, we have been working to solve microbial contamination problems for people, in a way that restores their quality of life and doesn’t make remedial a heavier burden than the mold problem itself. On the other hand, it must be kept in mind that incomplete remedial will leave people with the old problem coming back again... All our experience has been built on the fragile equilibrium between " too much " and " not enough ". The following case study illustrates such a situation and how we dealt with it.

3 — Case Study : in search of the hidden mold

After the January 1998 ice storm, adminitrators of a Montréal office building hired us to make a complete microbial evaluation of the premisses. Five occupants, out of 33, started to complain of asthma, flue like symptoms, and severe headaches after the ice storm. Local health officials (CLSC) prompted evacuation of the third floor.

3.1 — Building History

The four level (three floors and a basement) office building, built in the fifties, with a total surface of 20 000 square feet, has an exterior brick cover and a concrete basement. Five roof top HVAC units are installed on the flat roof. Thermal insulation and fire retardant properties are provided by asbestos amosite fibers on the H beams of the structure. There has been some water leaks mainly from the roof but also from the basement, with a major worsening of the situation after the January 1998 icestorm.

3.2 — Health Investigation

A medical doctor, with experience in this field, after an information meeting with the occupants to assay the situation, concluded that at least 24 persons out of 33 were experiencing symptoms that could be associated with indoor microbial contamination. Symptoms diminished or altogether disappeared when the occupants left the building.

3.3 — On site investigation

Outside

Inspection of the HVAC roof top units has shown that they were very old, with inadequate maintenance, no access to the drain pans and that 10 inches of ice accumulation from the ice storm caused water infiltration and leaky joints all around the units, allowing large amounts of water inside the building.

First, second and third floors
Observations
  • Mold odor on the second and third floor.
  • Wet carpets removed on the third floor.
  • Obvious traces of extensive water infiltration from the roof, with water buckets in many places, especially near the ventilation ducts.
  • Leaky surfaces on walls and ceilings covered with plastic to prevent water dripping.
Surface sampling on adhesive tape
  • Fungal growth was found on the lower parts of certain walls, with the presence of visible Stachybotrys chartarum, on approximately 10 cm2 and Ulocladium on approximately 0.5 m2.
  • Fungal growth on carpet glue with 0.1 m2 of Stachybotrys chartarum and 0.5 m2 of Ulocladium.
  • Total visible fungal growth on a surfaceof approximately 1.5 m2, mainly on the third and second floors, nearest to the roof.
Bulk dust sampling
  • Dust sampling showed the presence of large amounts (over 1 million cfus per gram of dust) of Trichoderma viride, yeasts and Gram positive bacteria in the electrical wall board units of the third floor.
  • Carpet dust showed more than 12.5 millions cfus per gram of the same microbial distribution on the second floor and a million colonies per gram of Gram positive bacteria on the first floor.
  • Lesser amounts of microbes, with the same distribution, were found in HVAC system #4, on the third floor.
  • Finally, the roof top unit of HVAC system #1, for the first and second floor, was heavily contaminated with more than 5 millions cfus of Cladosporium per gram of dust.
Basement

Many sources of water infiltrations were present, but less extensive than roof leaking. The lower exterior brick cover was buried in the ground to level the outside area near the walls. This resulted in water infiltration inside the basement from the porous bricks, and small surfaces of visible Penicillium, on less than 0.1 m2.

3.4 — Remediation

Building evacuation

The investigation did not show extensive surfaces of mold growth but it did show extensive abnormal water activity. The " not enough " attitude would have prompted us to recommend to stop water activity from the roof and basement... and hope for the best. Simple cleanup of the water infiltration areas, without intensive inspection of the internal wall and ceiling structures would have been enough, because of insufficient evidence of mold growth.

The " too much " attitude would have prompted us to start panicking about the presence of the " deadly black mold " even on small surfaces, make unnecessary supplementary lab sampling and analysis, and lose credibility.

Even in the absence of large visible surfaces with mold growth, extensive water activity can cause hidden fungal contamination involving the building structure. Furthermore, dust sampling revealed contamination in many areas of the building, and occupants reported health symptoms. For these reasons, we recommended to evacuate the second floor and stop water infiltration by the roof in priority. The building administrators decided to evacuate all the building and we organized the microbial decontamination of the office equipment that was transferred in another building. After the occupants left the building, health symptoms either diminished or stopped entirely. Other recommendations followed, including the removal of asbestos and the fungal decontamination of all the premisses.

Asbestos abatement and microbial decontamination protocol

Since work had to be done on the structure, including asbestos covered beams, asbestos removal as well as microbial decontamination were included in detailed quotations. Demolition, asbestos abatement and microbial decontamination were handled by contractors under our supervision. Asbestos abatement procedures followed federal and provincial regulations. Microbial decontamination procedures were guided by New York Department of Heallth, Public Works, Health Canada and Canadian Mortgage and Housing Corporation recommendations. A special appreciation goes to Dr Philip Morey, whose work and publications are invaluable in establishing confinement levels and strategies on contaminated sites.

Discovering the hidden mold

After the retrieval of all the HVAC units, the roof was completely redone. Asbestos confinement and HEPA filter air extraction devices were put in place first on the third floor to control the removal of the fungal contaminated materials, including all the air ducts, than on the second, first and basement floors. Secondly, the asbestos fibers were taken away followed by the floor decontamination with a blast track machine. Finally, all the surfaces in the building were vacuum cleaned and wiped with a chlorine bleach solution.

As remediation proceeded, opening up of the wet structures revealed the presence of large surfaces of hidden mold growth, near the leaky ventilation ducting, where water infiltrated from the roof. This situation was not obvious during the initial walk through.

With the " not enough " attitude, not opening the structures, the mold would not have been dicovered. But extensive water activity and health complaints from occupants called for opening up of the structures. This decision was indeed the right one: a total hidden surface of more than 10 m2 was contaminated by Stachybotrys chartarum mold growth, mostly in the bathrooms and the mechanical rooms.

4 — Conclusion

First, trust the occupants: if there are complaints, there is a cause, even if it’s not obvious. Find it! Second, a thorough inspection of the premisses and their ventilation is mandatory. Keep in mind that mold needs water and porous organic materials that can be hidden in the structures and not directly visible. Almost any building material can harbor fungal growth, if the available water activity is sufficient. Use the proper tools to find it. Third, if sampling is needed, be versatile: no sampling method is perfect. Adapt the sampling strategy to the situation and use an accredited mycology lab to count and identify fungi in your samples. Bear in mind that you could be dealing with toxigenic mold and, depending on the extent of the contaminated surface, take proper action to keep occupants away from it and protect their health. Finally, after putting together all the data gathered in the field, always communicate it in a simple, straightforward way, with affordable step by step remedial: don’t forget that people want to get rid of their problem, not make their lifes more complicated.

March 1999/03/24
Natur’Air-Kiwatin