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This Office Makes Me Ill

By Neil Carlson, M.S., CIH
Tom Kapfer, CIH
Arif Quraishi, M.E.

Studies have shown that the majority of the U.S. population spends over 90% of their time indoors, and that the indoor environment is significantly more contaminated than the outdoor environment. Therefore, it is critical to take steps to maintain as pollutant-free an indoor environment as possible to improve health of the building occupants and reduce liability for building owners and managers, and improve the productivity of the building.

Indoor air pollutants are associated with or directly related to numerous health-related symptoms or complaints reported by building occupants. Some of these symptoms or complaints have been traced to biological contaminants, which can include the biological organism itself (a biological organism can be simple in structure, such as bacteria, or complex, such as a cat) or materials that the organism sheds, eliminates, or produces, such as:

• Fungi
• Bacteria
• Viruses
• Insect parts and feces

Fungi

The most effective means of avoiding fungal growth is to “keep the water out” by monitoring and avoiding the following conditions:

• High humidity levels
• Water leaks
• Moisture migration through masonry walls
• Condensation

Each of these conditions can have several causes or sources. For example, high humidity levels can be due to certain activities taking place in the building, such as operating a chilled water air conditioning system at too high a temperature. A comprehensive evaluation may be needed to determine the actual cause(s) of the water infiltration problem.

The following “rules of thumb” can help manage water infiltration:

(1) If growth has occurred on a hard surface, the surface can easily be cleaned. However, if growth has occurred on a porous surface, such as ceiling tile, the porous material should be carefully removed to prevent the uncontrolled release of a cloud of spores into the building’s environment.

(2) To avoid fungal growth in porous materials (sheetrock, carpet, ceiling tile, etc.) where water infiltration has occurred, the material needs to be dried within 24 hours.

(3) When fungal-contaminated materials are removed, the work should be done under controlled conditions because airborne fungal levels can increase by a factor of 10 or more when fungal-contaminated materials are removed or disturbed. “Controlled conditions” means that steps are taken to prevent the spread of fungal contamination to clean areas and to protect building occupants and the abatement area from elevated fungal exposures.

Even though work related to the removal of fungal-contaminated materials is not regulated, OSHA and some state health departments are becoming concerned about exposure of fungus abatement workers and building occupants to fungal spores and other compounds. Therefore, if fungal contamination is present, an appropriate response is needed to not only protect the health of workers and building occupants, but also to avoid negative scrutiny by regulators.

Bacteria

In indoor environments, bacteria may be found in dust and water sources. Exposure to bacteria can cause disease, especially among individuals with compromised immune systems. One type of disease caused by bacteria is Legionellosis. Bacteria growing in mechanical cooling towers of buildings is usually the source of the contamination. The mist from cooling towers containing the bacteria can be inhaled and may affect individuals with compromised immune systems. Care in placing the cooling towers away from outside air intakes and providing continuous chemical treatment of the water and installing high efficiency drift eliminators will reduce this hazard.

Another potential illness is Humidifier fever, caused by an adverse reaction to the chemicals contained in the body of the bacteria. These bacteria can be spread by decorative fountains with inadequate chemical treatment or room humidifiers that are not appropriately cleaned. Humidifiers that are unfiltered and produce a cool mist are the most significant reservoirs for these bacteria. These humidifiers should be replaced with evaporative humidifiers that release water vapor but do not aerosolize the bacteria in a mist.

High bacteria levels have been found in wet building materials and can be the cause of offensive odors. Whether or not the bacteria may cause disease will depend upon the strain and levels of bacteria present. Of course, if the source of the water is from the sanitary sewer, we should assume that disease-causing bacteria are present and implement the appropriate preventative and corrective actions. Corrective action includes containment of the contaminated area and removal of all impacted porous building materials (e.g. carpet, sheetrock) using asbestos abatement type techniques and personal protection. After removal, all remaining surfaces should be disinfected with a 10% bleach solution followed by a clean water rinse.

Viruses

Viruses are primarily transmitted from person to person by coughing, sneezing and shaking hands. Viruses are most efficiently transmitted during the winter months when the relative humidity level is below 30%. In the northern part of the United States, this occurs inside buildings from late October through part of April. The spread of flu and cold viruses can easily be minimized by frequent hand washing with moisturizing soap, and by covering the nose and mouth when sneezing or coughing.

Insect Parts And Feces

Aside from their disagreeable appearance and potential to bite or sting, insects can affect the indoor environment with their fecal droppings. Fecal droppings contain allergens, which, if present at relatively high levels, may cause allergic-like reactions in sensitive individuals.

Most insects are large enough to be noticed and measures are usually implemented to eradicate them. However, some insects are too small to be readily seen and one such insect is the dust mite, which feeds on shed skin cells. Its fecal droppings are a strong allergen, and many people have been diagnosed with a dust mite allergy. Dust mites proliferate in an environment that is warm and relatively humid, and where people or animals and fabrics are present.

The best means for controlling dust mite populations include:

• Frequent cleaning of carpet and other textiles with a HEPA-filtered vacuum cleaner.
• Maintaining the indoor humidity at relatively low levels (dust mites tend to withdraw from areas with relative humidity levels of less than 50%).

Cockroach saliva and feces have also been identified as sources of allergens in the indoor environment. Aside from controlling cockroach populations through pest management, cleaning with a HEPA-equipped vacuum and other good housekeeping practices will help to reduce allergen levels.

Conclusion

With our ever increasing level of understanding related to the health impact of biological contaminants in indoor environments, it is critical that building owners and risk managers develop a comprehensive plan to reduce exposure to indoor biological agents. Simple steps, such as regular and daily cleaning of buildings, maintenance of the building envelope to reduce water infiltration, increasing the quantity of outside air, and conducting regular and routine preventive maintenance on HVAC systems will assure that health risk to building occupants and potential liability for the building owner are minimized. 

ABOUT THE AUTHORS

Neil Carlson is a mycologist with the University of Minnesota, Environmental Health & Safety Division. Tom Kapfer is the Technical Director and Arif Quraishi is the Vice President of the Indoor Environments Division at the Institute for Environmental Assessment, Minneapolis, Minnesota.

RELATED INFORMATION

Building Air Quality

riskVue | The webzine for risk management professionals
August 1999