Objectives: To compare exposure to secondhand smoke and respiratory health in bar staff in the Republic of Ireland and Northern Ireland before and after the introduction of legislation for smoke-free workplaces in the Republic.

Design: Comparisons before and after the legislation in intervention and control regions.

Setting: Public houses in three areas in the Republic (intervention) and one area in Northern Ireland (control).
Participants: 329 bar staff enrolled in baseline survey; 249 (76%) followed up one year later. Of these, 158 were non-smokers both at baseline and follow-up.

Main Outcome Measures: Salivary cotinine concentration, self reported exposure to secondhand smoke, and respiratory and sensory irritation symptoms.

Results: In bar staff in the Republic who did not themselves smoke, salivary cotinine concentrations dropped by 80% after the smoke-free law (from median 29.0 nmol/l (95% confidence interval 18.2 to 43.2 nmol/l)) to 5.1 nmol/l (2.8 to 13.1 nmol/l) in contrast with a 20% decline in Northern Ireland over the same period (from median 25.3 nmol/l (10.4 to 59.2 nmol/l) to 20.4 nmol/l (13.2 to 33.8 nmol/l)). Changes in self reported exposure to secondhand smoke were consistent with the changes in cotinine concentrations. Reporting any respiratory symptom declined significantly in the Republic (down 16.7%, -26.1% to -7.3%) but not in Northern Ireland (0% difference, -32.7% to 32.7%). After adjustment for confounding, respiratory symptoms declined significantly more in the Republic than in Northern Ireland and the decline in cotinine concentration was twice as great.

Conclusion: The smoke-free law in the Republic of Ireland protects non-smoking bar workers from exposure to secondhand smoke