Bacterial contamination of organic dusts: effects on pulmonary cell reactions.

The influence of water extracts from different organic dusts on the number of free lung cells was studied in short-term exposure experiments. A large increase in the number of leukocytes was found 24 hours after exposure to extracts from cotton and hay. The number of macrophages was not affected. The increase was greater when the dusts were incubated at 37 C and 100% relative humidity prior to the preparation of the extract. This procedure caused an increase in the number of bacteria. When different bacterial species were studied endotoxin-producing strains were found to cause the largest effect.