Smoker density
The observed smoker density ranges from 0.03 BC/100 m3 to 1.31 BC/100 m3, and averages 0.57 BC/100 m3, just 25% of the 2.32 BC/100 m3 expected at maximum occupancy.
Air exchange rates from the model
The default air exchange rate for a typical bar at maximum occupancy was derived by Repace [12] as C
v
= 18 air changes per hour (h-1). Using Eq. 1, C
v
is calculated for all 7 venues in Table 2, ranging from C
v
= 0.75 to 4.23 h-1, also much lower than expected, indicating these bars are underventilated.
Ventilation rates from CO2
Calculated V
o
values in Table 2 range from 5 to 29 L/s-occ, and average about 14 L/s-occ, close to the 15 L/s-occ specified by ASHRAE. However, the mean occupancy was 39 occupants per 1000 ft2, 39% of maximum occupancy for a bar, indicating that air quality would be much worse at busier times. This illustrates even if the ventilation rate for removal of CO2 is adequate, the air exchange rate for SHS removal can be inadequate because V
o
is not coupled to smoker density. It also illustrates that at full occupancy, none of the venues would have complied with ASHRAE Standards, showing that proper ventilation has been ignored in these venues.
Air pollution from SHS
Figure 3 plots the pre-ban RSP vs. the pre-ban PPAH. A regression analysis yields a good linear fit (R = 0.93) with a 2000:1 ratio between RSP and PPAH. This is in good qualitative agreement with previous research which shows that during smoking, the cigarette PPAH tracks the RSP, but has a higher decay rate [12]. Figure 4 plots the background-subtracted RSP vs. the background-subtracted PPAH values as a function of burning cigarette density and SHS-RSP air exchange rate using the habitual smoker model. The correlation of net RSP and net PPAH with each other and the increase of PPAH and RSP with active smoker density suggest a strong association with smoking, and interestingly, the slope of the regression differs only by 1% from that observed in the Wilmington Study [12].
By how much are the RSP and PPAH levels reduced by the smoking ban? From Table 2, excluding Pub # 6, which had the IAQ problem, the pre-ban pub RSP levels average 179 μg/m3. From Table 3, the post-ban pub RSP levels, again excluding Pub #6, average 7.7 μg/m3, a decrease by 96%. Similarly, From Table 2, excluding Pub #6, the pre-ban pub PPAH levels average 65.1 ng/m3. From Table 3, the post-ban pub PPAH levels, again excluding Pub #6, average 6.32 ng/m3, a decrease by 90%. If the calculations are referenced to the indoor/outdoor levels on April 18, the estimated SHS-RSP contribution is [(179-18.6)/179] = 90%, and the estimated SHS-PPAH level contribution is [(65.1-15.8)/65.1] = 76%. However the latter calculation may be an underestimate, since the PPAH level in the pubs on Oct. 17, 6.32 ng/m3, was about 70% of the outdoor level; if the PPAH outdoor level on April 18 is adjusted downward to 70% of its value (0.70)(15.8) = 11 ng/m3, and the estimated SHS-PPAH concentration recalculated, [(65.1-11)/65.1] = is 83%. Thus, a conservative inference from the data would be that SHS contributed about 90% to 95% of the RSP levels during smoking, and 80% to 90% of the PPAH levels during smoking, with an average smoking prevalence of about 12%. This compares to a state-wide smoking prevalence of 19.7% in 1999, as reported above.
But there was one major exception: Pub # 6, which had a higher RSP level after the smoking ban than before (although the PPAH level was much lower). Repace et al. (1980) [14] found that cooking smoke could contribute significantly to indoor air pollution. Kitchens are supposed to remain under negative pressure to contain cooking fumes [36]. However, Table 2 shows that Pub #6's CO level on April 18 was [(5.5-2.16)/(0.38)] = 8.8 standard deviations beyond the mean of the other pubs. Similarly, Table 3 shows that Pub #6's CO level on Oct. 17 was also high, at [(7.94-1.24)/(0.85)] = 7.9 standard deviations beyond the mean of the others. This suggests that Pub # 6 had an indoor air quality problem of another type. The Boston Public Health Commission (BPHC) was alerted, and conducted an investigation. The investigation discovered that a gas-fired deep-fat fryer had a yellowish flame instead of the expected blue, as a result of the burner being plugged with grease. These yellow flames emitted 50 ppm of CO into the kitchen, which permeated the rest of the premises, although the kitchen exhaust hoods were functioning (L. Bethune, Boston Public Health Commission, Office of Environmental Health, personal communication).
How do these air quality measurements compare with other studies? In a preliminary report on a similar model-based RSP study in 27 Boston hospitality venues with smoking, but with both pre- and post-ban data taken using an aerosol monitor, Connolly et al. (2005) [17] in a Harvard study, reported a mean estimated SHS-RSP of 207 μg/m3 (SD 202), and a median value of 121 μg/m3. Connolly et al.'s smoker density D
s
varied between 0 and 2.95 BC/100 m3, with a mean value of 0.89 (SD 0.73) compared to 0.57 (SD 0.44) in our study. Our mean pre-ban estimated SHS-RSP is (198 – 19) = 179 μg/m3 (Table 2), and a median value of 178 μg/m3 (not shown), and a mean estimated SHS-PPAH level of (61.7-15.8) = 46 ng/m3.
In a very similar model-based air quality survey to that reported here, Repace [12] measured RSP and PPAH in Wilmington, DE in 8 hospitality venues, a casino, 6 pubs, and a pool-hall. In the Wilmington study, active smoker density varied between 0.02 and 1.44 cigarettes per hundred cubic meters and averaged 0.53 (SD 0.54), and SHS contributed 90% to 95% of the RSP air pollution during smoking, and 85% to 95% of the carcinogenic PPAH, with an average smoking prevalence of 15%. Indoor RSP levels averaged 231 μg/m3 (SD 207), quite similar to the values reported by the Massachusetts Study [17]. Ott [38], in a model-base study, observed reductions of RSP 84% following California's smoking ban, in a 2-year longitudal study in a tavern in California, and reported that the active smoking count explained more than 50% of the variation in the RSP concentrations observed on individual visits [38].
Another model-based survey in Western New York State reported a range in smoker density in 14 bars and restaurant/bars from 0.25 to 3.15 BC/100 m3, averaging 1.36 BC/100 m3; the mean estimate SHS-RSP level was 385 μg/m3, and the total RSP pollution level declined by 93% after a state-wide smoking ban [39]. This is in good agreement with a study of the effectiveness of a state-wide smoking ban in New York State, where urine cotinine levels, a measure of SHS exposure, declined by 94%, from a pre-ban median of 4.93 ng/ml in non-casino hospitality workers (n = 36) to a post-ban level of 0.3 ng/ml (n = 27), the level of detection [30].
Similar results have been observed in Europe. Mulcahy et al. [23] randomly sampled 20 city centre bars in Galway, Ireland, for air nicotine concentrations before and after the Irish national smoking ban. They found an 83% reduction in air nicotine concentrations following the smoking ban. However, smoker density was not reported. Edwards et al. [37] conducted a cross sectional study in four mainly urban areas of the North West of England measuring a mean PM2.5 level of 285.5 μg/m3 (95% CI 212.7 to 358.3), in a stratified random sample of 64 pubs; smoker density was not reported. Levels were higher in pubs in deprived communities: mean 383.6 μg/m3 (95% CI 249.2 to 518.0) vs 187.4 μg/m3 (144.8 to 229.9). The highest outdoor levels observed were about 24 μg/m3 suggesting that overall, about 92% of the RSP levels might have been due to SHS. The UK will ban smoking in pubs in 2007.
The Boston pre-ban PPAH results 61.7 ng/m3 (SD 54.9), half of those found in the Wilmington air quality study, 134 ng/m3 (SD 86.5), whereas the smoker density varied from 0.03 to 1.31 in Boston, and averaged 0.57 (SD 0.44). However the average air exchange rate in the Boston study was higher, at 2.26 h-1 (SD 1.37), compared to 1.4 h-1 (SD 0.97) in the Wilmington Study. Further, to place the preban Boston PPAH results into perspective, they are compared with PPAH measurements in outdoor air measured in nine sites in Roxbury, a Boston neighborhood polluted by heavy diesel bus and truck emissions. Median Roxbury concentrations ranged from 4 to 57 ng per cubic meter (ng/m3), and averaged 18 ng/m3 over all sites [18]. Our PPAH levels average (61.7/18) = 3.4 times as high as on the most heavily travelled roadways in Boston. Finally, a regression of the SHS RSP vs. SHS PPAH yields a ratio of ~2030:1, in excellent agreement with the value of 2054:1 reported in the Delaware study [12].
Air quality and health
To place the predicted and observed levels of RSP into perspective, consider the U.S. Annual National Ambient Air Quality Standard (NAAQS) for particulate matter 2.5 microns in diameter or less (PM2.5), which encompasses combustion-related fine particulate by-products such as tobacco smoke, chimney smoke, and diesel exhaust. In 1997, the EPA promulgated a 24-hour NAAQS for PM2.5, of 65 μg/m3, not to be exceeded more than once per year, and an annual NAAQS for PM2.5 of 15 μg/m3, based on protecting human health [19, 20, 35]. The NAAQS for PM2.5 is designed to protect against such respirable particle health effects as premature death, increased hospital admissions, and emergency room visits (primarily the elderly and individuals with cardiopulmonary disease); increased respiratory symptoms and disease (children and individuals with cardiopulmonary disease); decreased lung function (particularly in children and individuals with asthma); and against alterations in lung tissue and structure and in respiratory tract defense mechanisms in all persons. [19]. PM2.5 and PM3.5 are closely related [21]. The annual average PM2.5 level for Boston (City Square) for 2001 was: 13.25 μg/m3 [34]. 90% of U.S. Counties have PM2.5 levels below about 16 μg/m3 [22]. The intent of the NAAQS is to limit risk to human health from exposure to particulate air pollution. The NAAQS does not apply de jure to indoor air quality because the U.S. Clean Air Act specifies only outdoor ambient air and as such is not an exposure standard, however, this health-based standard may be used de facto to evaluate levels of indoor air quality provided averaging times are taken into account. We did not consider using OSHA workplace standards as a basis of comparison, because they are far less protective of human health than EPA standards. Recent research on the adverse health effects of fine particle pollution shows estimated concentration-response functions that are approximately linear, with no evidence of safe threshold levels; moreover, unresolved gaps in understanding exist concerning who is most at risk or most susceptible [10].
The average pre-ban SHS PM3.5 level in the 6 pubs (excluding Pub #6) was 179 μg/m3, and post-ban 7.73 μg/m3. Subtracting post-ban background, and assuming pub staff work 260 days per year, 8 hrs per day, they are exposed to an annual average of (171 μg/m3)(260 d/365 d)(8 hr/24 hr) = 40.6 μg/m3 from SHS, and to an annual average background level of 13.25 μg/m3 from outdoor non-SHS sources. Assuming that these averages are sustained over the required 3 year averaging period, SHS exceeds the 15 μg/m3 level of the Annual National Ambient Air Quality Standard by a factor of (40.6 + 13.25)/15 = 3.6. Although no standards have been set for PPAH, assuming an 8-hr workday, on a 24-hr average basis for the 7 venues sampled, pre-ban PPAH exceeded post-ban PPAH levels by a factor of [(65.1/3) + 6.32)]/6.32 = 4.1, significantly increasing exposure of workers to substances known to be implicated in the causation of cancer, heart disease, and stroke [12, 31, 32].
Figures 1, 2, and 3 taken together demonstrate conclusively that secondhand smoke causes most or a significant fraction of the massive RSP and PPAH pollution elevations shown in 6 of 7 hospitality venues of Figure 1. Smoking in these Massachusetts hospitality venues caused levels of respirable particles and particle-bound PAH carcinogens exposure to increase by six-to-ten-fold. The models developed from Equation 1 generalize the results to other hospitality venues. Finally, the elevated carbon monoxide levels and heavy RSP pollution in Pub #6 before and after the smoking ban suggest that the kitchen exhaust equipment has broken down and grilling fumes are being pulled into the dining room along with cooking gas fumes from a defective deep-fat fryer. Overall, RSP levels decreased from 179 μg/m3 to 8 μg/m3, or by 96% and PPAH levels decreased from 65 ng/m3 to 6 ng/m3, or by 90%. There are few public policy interventions that require such a small public investment and that yield such a dramatic return in such a short period of time.
Health risk assessment for workers and patrons
What are the disease risks of SHS-RSP at the odor and irritation thresholds? Repace et al. estimated [27] that lung cancer and heart disease mortality risk combined from workplace SHS (annualized workplace exposure of 6.7 hours daily) for a working lifetime of 40 years was 150 deaths per million persons at risk per 1 μg/m3. Since the federal (EPA) de minimis risk level is 1 death per million workers at risk, at the lowest odor threshold ever measured, the risk from passive smoking is 150 times de minimis risk, and at the lowest irritation level ever measured, 600 times de minimis risk. the de minimis risk is defined as a level "below regulatory concern" [28]. In other words, if SHS can be smelled, it's at harmful levels.
At the 179 μg/m3 level SHS-RSP averaged over all venues, the chronic risk of these two diseases combined is (179/1)(150 × 10-6) = ~27 deaths per 1000 workers per 40 year working lifetime. This exceeds the Occupational Safety and Health Administration's Significant Risk of Material Impairment of Health level of 1 death per 1000 per 45 years [27] by a factor of (45/40)(27 per 1000)/(1 per 1000) = 30-fold. Thus these exposures were quite significant [28] by U.S. federal risk assessment standards for occupational and environmental health.
Air Quality forecasts are provided by State and local agencies, using the U.S. Environmental Protection Agency's (EPA) Air Quality Index (AQI) [22], a uniform index that provides general information to the public about air quality and associated health effects. These index descriptors are described in Table 4. Health advisories and warnings are based on the current AQI as well as the forecasted AQI. Air quality authorities maintain running averages for each pollutant, and an appropriate AQI is reported that generally corresponds to the current average. For most major cities, air quality forecasts, based on predicted meteorological conditions and monitored air quality, are also released to the public usually during the afternoon hours of the day preceding the forecast period. These forecasts are for PM and ozone, since these are the pollutants that generally contribute to unhealthy air quality. If pollutant levels are expected to be unhealthy, the state and local agencies will release a color-coded health warning or advisory to the local media and post these advisories on their web sites [22]. The color codes and corresponding normalized Air Quality Indices are based upon "break-points" or ranges of minimum-to-maximum particulate levels corresponding to increasing severity of expected health effects. AQI values are usually below 100, with values greater than 100 occurring at most several times a year. The SHS-RSP levels in Table 5 for the 7 pubs range from AQI descriptors corresponding to Unhealthy for Sensitive groups (2), to Unhealthy (1), to Very Unhealthy (1), to Hazardous (3). This comports with Biener et al.'s [29] reported health reasons for nonsmokers' aversion to SHS. The air pollution levels overall correspond for all venues to a level of 198 μg/m3, or Very Unhealthy.