UK smoke-free legislation: changes in PM2.5 concentrations in bars in Scotland, England, and Wales.

OBJECTIVE Evaluate the effect of smoke-free legislation on fine particulate [particulate matter <2.5 microm in diameter (PM(2.5))] air pollution levels in bars in Scotland, England, and Wales. DESIGN Air quality was measured in 106 randomly selected bars in Scotland, England, and Wales before and after the introduction of smoking restrictions. METHODS PM(2.5) concentrations were measured covertly for 30-min periods before smoke-free legislation was introduced, again at 1-2 months post-ban (except Wales) and then at 12-months post-baseline (except Scotland). In Scotland and England, overt measurements were carried out to assess bar workers' full-shift personal exposures to PM(2.5). Postcode data were used to determine socio-economic status of the bar location. RESULTS PM(2.5) levels prior to smoke-free legislation were highest in Scotland (median 197 microg m(-3)), followed by Wales (median 184 microg m(-3)) and England (median 92 microg m(-3)). All three countries experienced a substantial reduction in PM(2.5) concentrations following the introduction of the legislation with the median reduction ranging from 84 to 93%. Personal exposure reductions were also within this range. There was evidence that bars located in more deprived postcodes had higher PM(2.5) levels prior to the legislation. CONCLUSIONS Prior to legislation PM(2.5) concentrations within bars across the UK were much higher than the 65 microg m(-3) 'unhealthy' threshold for outdoor air quality as set by the US Environmental Protection Agency. Concentrations in Scottish and Welsh bars were, on average, two or more times greater than in English bars for which seasonal influences may be responsible. Legislation in all three countries produced improvements in indoor air quality that are consistent with other international studies.