Abstract
This study examines the effect of sub-micrometer aerosols of motor oil on the irritant potency of sulfur dioxide. The increase in pulmonary flow resistance in guinea pigs was used as the bioassay of irritant response. When administered simultaneously, both unused and used motor oil protected against the irritant response to sulfur dioxide. This protective effect was lost when the oils had been previously reacted with sulfur dioxide. the additives used in the motor oil provided an equivalent protection when dissolved in a mineral oil which alone did not protect. Pre-exposure to motor oil did not provide protection. Sulfur dioxide and motor oil given together as a pre-exposure provided protection against further exposure to sulfur dioxide.