Nebot et al. to the option taken after the law came into force. We found a significant reduction (96.7%) in places that became smoke-free. In venues allowing a smoking zone, we observed a similar reduction (88.9%) in no-smoking zones, whereas in smoking areas the median concentration increased slightly (37.2%). Venues allowing smoking had a nonsignifi- cant reduction of 19.4%. Discotheques and pubs showed a nonsignificant reduction (from 33.3 to 15.1 gμ/m 3). Discussion Overall, the results confirm the positive impact of the law in the indoor workplaces and hospi- tality premises that became smoke-free after the law. The median nicotine concentration decreased by 60.0% in public premises and by 97.4% in private workplaces. A major reduction (96.7%) also occurred in bars and restaurants that became smoke-free and in the no-smoking zones of venues where sepa- rate spaces were allowed (88.9%). In smok- ing zones and in premises allowing smoking, including discotheques and pubs, no signifi- cant changes occurred. As expected, the pres- ence of SHS in bars allowing smoking, and in the smoking zones of those permitting separate zones, remained extremely high. Regarding differences in the proportions and nicotine levels between regions, stratifying by region, type of venue, and smoking regulation, the sample size in each stratum is too small to make statistically reliable comparisons. The results of our study are consistent with those of previous studies that use nico- tine in the air to evaluate the impact of smok- ing regulations. This method has proven to be both valid and sensitive and is therefore able to monitor changes in smoking policies with just a few samples. For example, seven discotheques and pubs were analyzed in Italy by Gorini et al. (2005), and 20 bars and pubs were studied in Ireland by Mulcahy et al. (2005). These studies found reductions in nicotine concentrations from 80% to 95% in bars that became smoke-free—percentages close to those found in our study. Studies using other indicators have also detected changes. Some of these studies have used either other airborne markers such as particulate matter with aerodynamic diam- eters ≤ 2.5 mμ (Goodman et al. 2007; Repace et al. 2006; Semple et al. 2007a; Valente et al. 2007) or biomarkers such as cotinine in saliva (Allwright et al. 2005; Semple et al. 2007b), and all have reported results very similar to ours. Furthermore, some of these studies used questionnaires to measure SHS exposure (Fong et al. 2006; Galán et al. 2007; Haw and Gruer 2007), although these studies can- not fully rule out some information bias. A limitation common to many of the studies evaluating the impact of smoking policies is the short interval considered after the ban, in most cases only some weeks or months after the law was introduced. Only a few (Allwright et al. 2005; Goodman et al. 2007) have looked at the indicators 1 year after the law was enacted. As far as we know, only one study carried out in Italy (Gorini et al. 2008) evaluated the impact of the smok- ing policy 2 years after the implementation, showing an important decrease in nicotine concentrations even 2 years after the smoking ban. However, more studies are needed to Table 2. Median nicotine concentration (µg/m3) in workplaces at baseline and at the 12-month follow-up. Median nicotine concentration (IQR) 12-month follow-up Percent variation Smoking permitted throughout the premisesb 7.07 (1.86–11.78) Smoking permitted in designated areasb aWilcoxon signed-rank test. bSmoking regulation after the law; at baseline, smoking was permitted in all venues. Median nicotine concentration (IQR) Baseline 12-month follow-up Percent variation p-Valuea 2.71 (1.39–3.77) 5.58 (2.42–12.42) 5.58 (2.42–12.42) 0.09 (0.01–0.26) 5.70 (2.77–11.73) 8.89 (5.28–15.61) 0.62 (0.34–1.40) 33.31 (10.79–79.65) 15.06 (6.77–56.92) –96.7 –19.4 37.2 –88.9 –54.79 < 0.001 0.191 0.075 0.036 0.241 Baseline 0.20 (0.06–0.57) 0.46 (0.12–1.13) 0.12 (0.06–0.38) 0.20 (0.06–0.64) 0.21 (0.08–0.50) 0.39 (0.07–1.29) 0.41 (0.05–1.40) 0.39 (0.08–1.30) 0.08 (0.01–0.18) 0.13 (0.03–0.20) 0.08 (0.01–0.20) 0.05 (0.01–0.11) 0.07 (0.01–0.15) 0.01 (0.01–0.16) 0.06 (0.01–0.18) 0.01 (0.01–0.15) –60.0 –71.7 –33.3 –75.0 –66.7 –97.4 –85.4 –97.4 p-Valuea < 0.001 0.006 0.020 < 0.001 < 0.001 < 0.001 < 0.001 < 0.001 Setting Public administration Local administration Regional administration National administration Universities Private sector Small (< 10 workers) Medium (10–50 workers) aWilcoxon signed-rank test. follow-up. Setting Bars/restaurants Smoking bannedb Smoking area Nonsmoking area Discotheques/pubs Smoking allowedb 346 Table 3. Median nicotine concentration (µg/m3) in hospitality venues at baseline and at the 12-month rule out a possible “decay” effect of the smok- ing policies over the time. This is the first study to show the impact of the Spanish law on SHS by using airborne markers and is among the few studies show- ing changes both in indoor workplaces and in hospitality sector venues. We have studied nearly 400 air samples, thus yielding by far the largest sample used in this kind of study. In pubs and discotheques, filters were exposed for shorter periods (4–5 hr) than in other settings, which may have impaired com- parability with other settings. However, we chose these time periods because typically these venues have most clients on the weekends and some are open only at this time. Therefore, exposing a filter for a whole week would have underestimated the real exposure. Because nic- otine concentrations in these settings during working hours is very high (López et al. 2004, 2008; Nebot et al. 2005), a minimum of 4 hr is sufficient to detect the presence of nicotine above the minimum detection limit. We made measurements using the same procedure both sampling periods (before and after measure- ments), thus ensuring accurate estimation of changes in nicotine concentrations. Another possible limitation could be the absence of a control group. However, control groups in evaluative public health research are not always necessary (or even possible) due to the complexities of the interventions evaluated (Victora et al. 2004). In this case, the characteristics of the law regarding the hospitality sector (i.e., permitting bars to choose between being smoke-free or non- smoke-free) allow the possibility of having two groups with different behaviors after the law, enabling comparison between hospitality premises that allow smoking and those that were smoke-free. Furthermore, the present study is a before-and-after study, in which comparison between the measurements taken before and after the law provide a valid and reliable estimate of the impact of the law. Overall, this study shows the posi- tive impact of the law in reducing SHS in indoor workplaces such as offices and pro- vides a precise description of the law’s lack of effect in the hospitality venues that did not become smoke-free—a result that was largely anticipated by tobacco control advo- cates (Cordoba et al. 2006). In addition, this study shows the strong impact of smoke-free policies in the air of the few bars and restau- rants banning smoking. In terms of public health, a large reduction in exposure has been achieved. However, workers in the hospitality sector remain exposed to very high levels of SHS, and therefore the situation cannot be considered satisfactory. Assuming that approximately 80% (Martín- Luengo 2007) of hospitality workers in Spain (1,400,000) (Instituto Nacional de Estadística ovlume 117 | number 3 | March 2009 • Environmental Health Perspectives