Changes in environmental tobacco smoke (ETS) exposure over a 20-year period: cross-sectional and longitudinal analyses

Abstract

AIMS:  To examine long‐term changes in environmental tobacco smoke (ETS) exposure in British men between 1978 and 2000, using serum cotinine. DESIGN:  Prospective cohort: British Regional Heart Study. SETTING:  General practices in 24 towns in England, Wales and Scotland. PARTICIPANTS:  Non‐smoking men: 2125 studied at baseline [questionnaire (Q1): 1978–80, aged 40–59 years], 3046 studied 20 years later (Q20: 1998–2000, aged 60–79 years) and 1208 studied at both times. Non‐smokers were men reporting no current smoking with cotinine < 15 ng/ml at Q1 and/or Q20. MEASUREMENTS: Serum cotinine to assess ETS exposure. FINDINGS:  In cross‐sectional analysis, geometric mean cotinine level declined from 1.36 ng/ml [95% confidence interval (CI): 1.31, 1.42] at Q1 to 0.19 ng/ml (95% CI: 0.18, 0.19) at Q20. The prevalence of cotinine levels ≤ 0.7 ng/ml [associated with low coronary heart disease (CHD) risk] rose from 27.1% at Q1 to 83.3% at Q20. Manual social class and northern region of residence were associated with higher mean cotinine levels both at Q1 and Q20; older age was associated with lower cotinine level at Q20 only. Among 1208 persistent non‐smokers, cotinine fell by 1.47 ng/ml (95% CI: 1.37, 1.57), 86% decline. Absolute falls in cotinine were greater in manual occupational groups, in the Midlands and Scotland compared to southern England, although percentage decline was very similar across groups. CONCLUSIONS:  A marked decline in ETS exposure occurred in Britain between 1978 and 2000, which is likely to have reduced ETS‐related disease risks appreciably before the introduction of legislation banning smoking in public places