Environmental Engineering Reference
In-Depth Information
scientists, however, believe that any measurable level of Bla g II in floor dust
is of medical concern.
It is rare to find floor dust levels in suburban areas >2 U/g; consequently,
there are few cockroach allergen-sensitized children in such environments.
In low-income urban areas, floor dust from 25 to 75% of houses sampled
contained
2 U/g Bla g II; consistently, a high percentage of children in
these homes have been sensitized. Such sensitization appears to be a major
risk factor for symptomatic asthma. In low-income areas, 40 to 60% of
asthma patients are sensitive to cockroach allergens. The prevalence of sen-
sitization to cockroach allergens among asthmatic and nonasthmatic emer-
gency room patients in Atlanta, GA, and Wilmington, DE, can be seen in
concentrations as high as 1000 U/g in heavily infested houses. Highest
concentrations occur in houses where cockroaches have been observed;
however, 20% of houses without any visible cockroach infestation have
detectable Bla g II in dust samples.
Little is known of the aerodynamic behavior of particles containing
cockroach allergens. Scientific speculation suggests that such particles are
likely to be large (>10
≥
m). As a result, they may not remain airborne for
long (<1 hour). Evidence for a link between the presence of cockroach aller-
gens and asthmatic/allergic symptoms is indirect.
The American cockroach,
Periplaneta americanus
(
Figure 5.5
)
, is the larger
of the building (mostly residences)-infesting cockroaches. It is approximately
38 mm long, with reddish brown wings. Because it is a common inhabitant
of sewer systems, basements in buildings may become infested following
heavy rains. It is commonly found in restaurants, supermarkets, bakeries,
etc. Unlike the German cockroach, it is also found outdoors, particularly in
states with moderate winter temperatures. Adult females typically live an
average of 440 days.
Limited information is available on the allergenicity of the American
cockroach. Antibody tests indicate that
P. americanus
allergens cross-react
with
B. germanica
antibodies, thus making it more difficult to distinguish
between the two types of sensitization.
µ
VI. Animal allergens
Many mammalian and avian species produce allergens that cause immuno-
logical sensitization and symptoms of chronic allergic rhinitis and asthma.
These include the danders of cats and dogs; rodents such as rats, mice, and
guinea pigs; and birds (feathers) kept indoors as pets.
There are approximately 100 million domestic animals in, or in close
proximity to, residences in the U.S. Indeed, 35 to 50% of residences in the
U.S. keep mammalian pets, most of which are housed indoors. Not surpris-
ingly, sensitization to cat and dog allergens is common. Sensitization to cat
dander among asthmatics varies from 9 to 41%. The highest level of sensi-
