Infectious agents (e.g., bacteria, fungi) are always present in the air, on environmental
surfaces, and as part of contact with other persons. Bioaerosols
are microscopic organisms in the air we breathe, are always present in the environment,
and pose no problems when kept within reasonable limits. Although bacteria cause
many odors in indoor environments (e.g., human body odor, locker room odors, sour
milk), exposure to such bacteria is rarely harmful.
Rarely, specific infectious agents can become so populous that they pose a particular
health risk. When excessively concentrated bioaerosols are inhaled, they can cause
disease. The most serious risks are to immunologically compromised individuals.
There are many examples: humidifiers may harbor bacteria and cause pneumonia,
rhinitis (i.e., runny nose), and other respiratory infections; accumulation of
bird droppings (feces) can carry infectious fungi (e.g., Histoplasmosis,
Cryptococcosis); human contact with
rodent droppings can lead to hantavirus
infection; human contact with parasites and bacteria in feces of cats, dogs, fowl,
and reptiles can cause diseases such as toxoplasmosis
and salmonella. Untreated water
reservoirs can release bioaerosols or attract disease-transmitting insects (e.g.,
mosquitoes), which may increase the risk for West
Nile virus, Legionella disease,
Birds, mice, rats and bats should not be allowed to colonize in attics, air intakes, or other areas near schools where people are likely to be exposed to fecal aerosols. Utilize methods to discourage migrating birds from congregating on school grounds. Any accumulated bird or rodent droppings should be treated to kill disease-causing organisms and then removed when the building is unoccupied.
Regularly clean ventilation systems and carpets. Prevent build-up of dirt and moisture. Immediately attend to unusual situations that could result in bioaerosol problems (e.g., wet carpets). Stagnant water should not be allowed to collect in ventilation system drain pans. Aerosol humidifiers should not be used in schools unless specific cleaning protocols are followed for preventing growth of infectious agents. Keep trash cans tightly covered and keep rain gutters clear of obstruction to prevent accumulation of standing water, a breeding ground for mosquitoes.
Center for Infectious Diseases (68) has resources that
are disease-specific (e.g., salmonella, West Nile virus, etc.) and provides tips
on disease prevention through management of the physical environment, such as
preventing accumulation of standing water and taking caution with animal feces.
Conference of Governmental Industrial Hygienists (14)
has resources targeted to building managers such as school custodians.
American Conference of Governmental Industrial Hygienists. School Workers Health and Safety Guide. 3rd Ed. CCOHS Publication #9760, 2001.
American Conference of Governmental Industrial Hygienists. Industrial Ventilation: A Manual of Recommended Practice. 24th ed. Cincinnati, OH: American Conference of Governmental Industrial Hygienists; 2001.
American Conference of Governmental Industrial Hygienists. Guidelines for the Assessment of Bioaerosols in the Indoor Environment. Cincinnati, Ohio; 1989.
Emmons CW. Saprophytic sources of Cryptococcus neoformans associated with the pigeon (Columba livia). Am J Hyg. 1995;62:227-232.
Michel O, Ginanni R, Duchateau J, Vertongen F, LeBon B, Sergysels R. Domestic endotoxin exposure and clinical severity of asthma. Clin Exp Allergy. 1991;21:441-448.
National Center for Infectious Diseases. An Ounce of Prevention: Keeps the Germs Away. Available at: http://www.cdc.gov/ncidod/op/handwashing.htm.