TABLE 3.1 Biological Particles That May Be Present in Indoor Air and Their Sizes

Source Organism

Particle

Size Range (μm)

Common Examples

Unique Characteristics

Virus

One or more virions in droplet nucleus

<0.1-3

Influenza

Particle may be much larger than organism; RNA or DNA, not both

Mycoplasma

One or more organisms in droplet nucleus

1-5

M. pneumoniae

No cell wall

Chlamydia

One or more organisms in droplet nucleus

1-5

Chlamydia psittasi

 

Rickettsia

One or more organisms in droplet nucleus

1-5

Coxiella burnetii

Obligate intracellular pathogen

Bacteria

One or more bacteria in droplet nucleus or on a raft

1-5

Micrococcus luteus

Variable in size, shape, cell wall composition

 

Single or grouped dry spores

0.5-5 3

Bacillus cereus Thermoactinomyces

Highly resistant endospores

 

Cell wall fragments

<0.1

 

 

Algae

One or more cells

5-10

Chlorococcus

Chlorophyll, cellulose

Nonvascular plants

One or more spores

15-30

Mosses

Chlorophyll, cellulose

Vascular plants

Spore

15-30

Lycopodium ferns

 

 

Pollen

10-50

Trees, grasses, weeds

Sporopollenin

 

Pollen allergens

?

 

 

 

Hairs

10-100

 

Cellulose

 

Fragments

?

Soy beans

Cellulose

Arthropods

Fragments

?

Cockroach, dust mite

Chitin

 

Fecal material

20-30

 

 

Animals

Fragments

?

Cats, dogs, mice

Keratin

 

Skin scales

10-50

 

 

Fungi

One or more spores

1.5-100

Mushrooms, aspergillus

Chitin

 

One or more hyphae

1.5-100

 

Ergosterol

 

Fragments

?

 

1-3 β-d-glucan

Particle sizes range from less than 0.1 micrometers to more than 100 micrometers and can vary with relative humidity. Spores are generally smaller in air than when mounted in liquid media for microscopy. In addition to particles directly derived from living organisms, other particles in air may also share properties with the bioaerosols. Some examples include latex particles and combustion products derived



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