These biological particles are almost always present outdoors. Their types and viability can change with time of day, season, weather and geographic location. Many sources of bioaerosols are man-made, such as sewage and animal waste disposal facilities. Bioaerosols can be inhaled by other animals and cause infection. Dust levels in an animal house are relatively high, especially when dry feeding or large quantities of friable bedding are used.
Concentration is affected by animal activity and building ventilation.
In general, concentrations of bioaerosols will be higher in animal houses than residential, industrial, or ambient settings. Higher bioaerosol levels occur when dust is stirred up during cleaning, feeding, or handling of the animals. There is an interest in the effect of bioaerosols released into the natural environment. Deposition of airborne particles occurs by gravitational fallout or by wind impaction onto surfaces. Costs of bioaerosols to humans and agriculture can be severe.