Changes in the lung lipids of rabbits and guinea-pigs exposed to the inhalation of silica dust

Eight rabbits and 24 guinea-pigs were exposed to a silica dust cloud of about 40,000 pp./ml. (0·3-3·0 μ) and killed at four-weekly intervals up to 30 weeks. The guinea-pigs showed an increase of lung lipid and phospholipid; the latter showed a parallel with the rising collagen level estimated chemically. In the rabbits there was no increase of either lipid or phospholipid. The likely explanation is that the silica did not reach the lungs in sufficient quantity.