The latter is a primary example of a material which is in part a bioaerosol (because it is microbially derived) and a dust (because of its size and nonviable nature). Seedorf et al. (1998) reported from a survey of cattle, pig, and poultry housing units in four European countries that cattle houses had the lowest endotoxin concentrations whereas poultry houses had the greatest with a mean of 692 and 49 ng/m3 for inhalable and respirable particulates,respectively.