Biological contaminants —illness syndromes; bacteria; viruses; and exposures to insect, mite, and animal allergens - Indoor Environmental Quality - page 154

Figure 5.4 Seasonal changes in dust mite populations. (From Arlian, L. et al., J.

Allergy Clin. Immunol ., 69, 527, 1982. With permission.)

Fecal pellets and mite body parts are the major sources of mite allergens.
Four allergen groups have been identified. Groups I, III, and IV allergens
are digestive enzymes; Group II allergens are associated with body parts.
Group I allergens such as Der p I and Der f I have received considerable
research attention. They are commonly measured in floor dust samples to
determine the dust sensitization potential for exposed populations. Com-
bined concentrations of Der f I and Der p I of <2 µ g/g dust are considered

to be a low sensitization risk; 2 to 10 g/g,

high risk for both sensitization and acute asthmatic attacks ( Table 5.5 ) . Rel-
ative concentration categories of mite allergen (as well as cat and dog aller-
gens) in house dust is summarized in Table 5.6 .
Mite numbers in floor dust have been used as indicators of sensitization
risk. The threshold for immunological reactions has been reported to be
approximately 100 mites/g. Since mite populations vary seasonally, low mite
populations may not be indicative of allergen levels which persist for months
after populations begin to decline.

µ g/g, moderate risk; and >10 µ

Table 5.5 Exposure Guideline Values for Common Indoor Allergens

Risk of
asthmatic attack Sensitization risk

Allergens low moderate high high

Dust mite 2 µ g/g 2-10 µ g/g >10 µ g/g >10 µ g/g

Cockroach <2 U/g >2 U/g >2 U/g >2 µ g/g

Cat <1 µ g/g 1-8 µ g/g >8 µ g/g >8 µ g/g

Dog ? ? ? ?

? = unknown.