Pulmonary changes due to low level occupational exposure to ozone.

The authors examined 31 workers employed in a chemical factory, exposed to ozone levels of less than 1.0 mg/m 3 (0.16-0.92) for about two years. The examination included: E.C.S.C. questionnaire for chronic bronchitis, spirography (FVC, FEV 1.0), MEFV (V̇ max50% FVC, V̇ max25% FVC) and acetylcholinesterase activity (ACC). Significant differences were found only in maximal expiratory flow rates compared to a control group from the same factory. Allowing for smoking habits, these differences were found only between exposed and non-exposed smokers. Respiratory function was examined in 21 workers after 0, 2, 4, 6 hours of a work shift: only five subjects showed significant decreases in V̇ max25% FVC. ACC measured at the end of a work shift was reduced in five subjects and returned to normal values after three weeks of non-exposure. This result confirms the inhibitory effect of ozone on ACC but it does not suggest that bronchoconstriction induced by ozone is mediated by the action of ozone upon ACC. Our results show that chronic exposure to low levels of ozone causes impairment of the small airways in smokers and confirm the validity of a TLV of 0.1 p.p.m. (ACGIH).