Investigation of the impact of smoke-free legislation in Northern Ireland on second hand smoke exposure of adult non-smokers living with smokers:

On 30th April 2007 legislation was introduced in Northern Ireland to prevent smoking in enclosed public places and workplaces. A baseline study (phase 1) was carried out in five geographical areas in Northern Ireland, before the introduction of the legislation on second hand smoke exposure, for adult non-smokers who live with at least one smoker. A follow-up survey (phase 2) was carried out 12 months after phase 1 to investigate whether residential second hand smoke exposure levels had changed following the introduction of the legislation. Airborne nicotine measurements were carried out in 84 homes in phase 1, of which 44 participated again phase 2. Airborne nicotine measurements were carried out using passive and active monitoring techniques. The geometric mean nicotine concentration measured with the passive samplers was 0.2 μg/m3 in phase 1 and 0.6 μg/m3 in phase 2. The geometric mean based on the active measurements was 2.3 μg/m3 in phase 1 and 3.4 μg/m3 in phase 2. Results from passive measurements in the homes that participated in both surveys showed a statistically significant increase in nicotine levels by a factor of 2.2, although no statistically significant increase was observed for the results from the active measurements. The increase in nicotine levels was predominantly observed in homes where the nicotine concentration was relatively low in the first survey. Statistical modelling showed that the difference between the two surveys was statistically significant for the data collected with the passive monitors, even after taking into account the effect of residential smoking patterns. This suggests that the increase in nicotine concentrations cannot be explained entirely by any changes in smoking levels. Other factors such as outdoor weather conditions resulting in increased ventilation in the house could play an important role in explaining the difference. Further follow-up studies are recommended to investigate long-term trends in the residential SHS exposures and to study the underlying reasons for the difference in results between the active and passive sampling techniques.