5 June 2003
Biological Air Pollutants. Biological air pollutants are found to
some degree in every home, school, and workplace. Sources include outdoor
air, human occupants who shed viruses and bacteria, animals (e.g., insects and
mammals) that shed allergens, indoor surfaces, and water reservoirs where fungi
and bacteria can grow, such as in humidifiers. A number of factors allow
biological agents to grow and be released into the air. Especially important is
high relative humidity, which encourages house dust mite populations to increase
and allows fungal growth on damp surfaces. Note that mold can grow on "dry"
surfaces in areas prone to high humidity levels (80% or more). Mite and fungus
occur when carpet is installed on poorly ventilated concrete floors), inadequate
exhaust of bathrooms, or kitchen-generated moisture. Appliances such as
humidifiers, dehumidifiers, air conditioners, and drip pans under cooling coils (as
in refrigerators) support the growth of bacteria and fungi.
Reactions. Certain individuals may react to mold exposure more
severely and quickly than others. These individuals include:
Infants and children
Elderly men and women
Individuals with respiratory conditions, allergies or asthma
Persons with weakened immune systems (i.e. persons with HIV
infection, chemotherapy patients, organ/bone marrow transplant
recipients, persons with autoimmune diseases
While only a small number of molds and fungi (see definitions on
page 26) are considered toxic and allergenic, species such as Stachybotrys atra
(S. atra), "Black Mold," gained public notoriety during the early 1990's when it
was linked by the Center for Disease and Control (CDC) to 10 cases of lung
disorder in infants and 100 other cases. In 1993, there were a number of cases
of acute pulmonary hemorrhage in nearly 30 infants after homes were flooded.
The CDC does not completely know the specific cause of these deaths.
However, they eventually concluded that significant exposure to Stachybotrys
atra (S. atra), in addition to other molds, played a significant role in the
development of this severe and fatal lung disease. Other fungi that cause
infection include Coccidioides, Histoplasma, and Blastomyces. However, these
fungi are rarely found indoors, growing instead in soil and dirt. Human contact is
usually due to contact with animals. Note: not all black mold is Stachybotrys.
Common Health Effects. Although mold affects individuals
differently and to different degrees, the following are some of the most common
adverse health effects: