SHS concentrations before and after implementation of the tobacco control law
| 2013 | 2018 | P value* | |
| Characteristics of monitored venues | |||
| No of venues | 24 | 27 | |
| Location† | 0.947 | ||
| Hanoi (n (%)) | 14 (58.3) | 16 (59.3) | |
| Ho Chi Minh City (n (%)) | 10 (41.7) | 11 (40.7) | |
| Type of venue | 0.999 | ||
| Restaurant (n (%)) | 9 (37.5) | 10 (37.1) | |
| Coffee shop (n (%)) | 8 (33.3) | 9 (33.3) | |
| Cafeteria (n (%)) | 7 (29.2) | 8 (29.6) | |
| Smoking policy | 0.451 | ||
| Smoking venues (n (%)) | 6 (25) | 4 (14.8) | |
| Partial venues (n (%)) | 11 (45.8) | 17 (63) | |
| Smoke-free venues (n (%)) | 7 (29.2) | 6 (22.2) | |
| Observation information‡ | |||
| Volume, m3 (mean±SD) | 183.7 (137.4) | 331.1 (381.1) | 0.036 |
| Ventilation system (n, % yes) | 21 (87.5) | 20 (74.1) | 0.228 |
| No of people (mean±SD) | 21.2 (8.5) | 19.4 (6.5) | 0.657 |
| No of smokers (mean±SD) | 6.8 (1.5) | 4.6 (3.3) | 0.008 |
| No of cigarettes smoked (mean±SD) | 13.8 (4.5) | 8.9 (5.7) | 0.012 |
| Active total smoker density, smokers/m3 (mean±SD) | 12.0 (4.6) | 5.6 (6.4) | 0.001 |
| Other burning sources (candles, fireplace etc) (n, % yes) | No | No | |
| Kitchen area open to the monitoring area | 8 (33.3) | 6 (22.2) | 0.375 |
| PM2.5 concentration‡ | |||
| Geometric mean (95% CI) | 93.1 (88.9–97.4) | 55.6 (53.1–58.2) | 0.05 |
| Mean (SD) | 138.7 (152.3) | 82.3 (92.8) | |
| Median (min max) | 72 (20–996.2) | 55.3 (5.8–913) | 0.01 |
| No. of venues with PM2.5 higher than the standard (n, %) | |||
| Vietnam, ambient air regulation§ | 17 (70.8) | 18 (66.7) | 0.75 |
| WHO standard¶ | 20 (83.3) | 24 (88.9) | 0.56 |
*Two-sample Kolmogorov-Smirnov test for quantitative outcomes and Kendall’s tau-b for categorical outcomes.
†Campaign 1 included only venues from Hanoi and Ho Chi Minh City to be consistent with campaign 2.
‡Analysis was based on a 30 min period during the busiest time for each venue in both campaigns.
§Ministry of natural resources and environment,43 24 hours standard of 50 µg/m3.
¶WHO 24 hours standard of 25 µg/m3.
SHS, secondhand smoke.