ASSOCIATION BETWEEN LIFETIME AMBIENT OZONE EXPOSURE AND PULMONARY-FUNCTION IN COLLEGE-FRESHMEN - RESULTS OF A PILOT-STUDY

Human health effects due to chronic exposure to ozone (O-3) have not b een established due to problems with exposure assignment and the use o f measures of lung function which may not reflect the site of O-3 toxi city in the lung. We investigated the feasibility of retrospective ass essment of O-3 exposure-relevant covariates and derived lifetime ''eff ective exposure'' to ozone. Mid- and end-expiratory hows (FEF25-75%, F EF75%) were regressed against effective exposure and ecological lifeti me exposure. A convenience sample of 130 UC Berkeley freshmen, ages 17 -21, participated twice in the same tests (residential history, questi onnaire, pulmonary function), 5-7 days apart. Students had to be lifel ong residents of Northern (SF) or Southern (LA) California. Monthly am bient O-3 concentrations (OZ) were assigned based on the lifetime resi dential history. An ''effective time'' (T) spent in OZ environments wa s derived for each residence and age stratum (0-2, 3-5, 6-11, 12+) wit h the use of questions about ''total time spent outdoors'' and time sp ent in ''moderate'' and/or ''heavy'' activity. Effective exposure was calculated over the lifetime (OZ x T) of each subject. Ozone metrics u sed were 8-hr averages (10 AM-6 PM) and ''hours above 60 ppb.'' FEF25- 75% and FEF75% decreased with both effective exposure and ecologic ass ignment of O-3 exposure. For a 20 ppb increase (interquartile range) i n 8-hr O-3 FEF75% decreased 334 ml/sec (95% Cl:11-657 ml/sec), which c orresponds to 14% (1.0-28.3%) of the population mean FEF75%. The corre sponding effect on FEF25-75% was -420 ml/sec (95% Cl: +46 to -886, P = 0.08) or 7.2% of the mean. Use of time-activity data to define exposu re had no impact on estimates. Negative confounding factors were regio n (SF vs LA), gender, and ethnicity. Lifetime 8-hr average O-3 concent rations ranged from 16 to 74 ppb with little overlap between regions. There was no evidence for different O-3 effects across regions. Effect s were independent of lifetime mean PM(10), NO2, temperature, or humid ity. Effects on FEV1 tended to be negative whereas those for FVC, alth ough negative in some models, where inconsistent and small. The strong relationship of lifetime ambient O-3 on mid- and end-expiratory flows of college freshmen and the lack of association with FEV1 and FVC are consistent with biologic models of chronic effects of O-3 in the smal l airways. Since the present study was designed as a pilot study, thes e findings have to be confirmed in a larger sample that is representat ive of the target population. (C) 1997 Academic Press