Table 3. Difference-in-Difference Model Results for Change in Air Quality Measures From Before to 12 Months After Smoke-Free Housing Policy Implementation Across 2 Low-Income Subsidized Housing Settings in NYC.
| Effect | Difference in particle concentrations before policy to 12 mo after policy, mean (95% CI), μg/m3 | Difference-in-difference estimate (95% CI) | P value |
|---|---|---|---|
| Airborne nicotine concentrationa | |||
| Stairwells | |||
| NYCHA | −0.29 (−1.03 to 0.45) | 0.03 (−0.99 to 1.06) | .95 |
| Section 8 | −0.32 (−1.04 to 0.39) | ||
| Hallways | |||
| NYCHA | −0.60 (−1.19 to 0.01) | −0.43 (−1.26 to 0.40) | .30 |
| Section 8 | −0.16 (−0.74 to 0.41) | ||
| Nonsmoking apartments | |||
| NYCHA | 0.12 (−0.01 to 0.24) | −0.04 (−0.24 to 0.15) | .67 |
| Section 8 | 0.16 (0.01 to 0.31) | ||
| Particulate matter <2.5 μm (unadjusted) | |||
| Nonsmoking apartments | |||
| NYCHA | −1.44 (−3.73 to 0.84) | 1.36 (−2.10 to 4.81) | .44 |
| Section 8 | −2.80 (−5.39 to −0.21) | ||
| Particulate matter <2.5 μm (adjusted)b | |||
| Nonsmoking apartments | |||
| NYCHA | 0.91 (−1.33 to 3.15) | 3.92 (0.59 to 7.25) | .02 |
| Section 8 | −3.02 (−5.49 to −0.55) | ||
| Cigarette butt count | |||
| Stairwells | |||
| NYCHA | −1.00 (−7.03 to 5.03) | 5.18 (−3.15 to 13.51) | .21 |
| Section 8 | −6.18 (−11.93 to −0.44) | ||
| Hallways | |||
| NYCHA | −2.20 (−4.09 to −0.32) | −1.70 (−4.30 to 0.90) | .19 |
| Section 8 | −0.50 (−2.30 to 1.30) | ||
Abbreviation: NYC, New York City; NYCHA, NYC Housing Authority.
a
Outcome, natural log of air nicotine concentration, or ln(nicotine).
b
Adjusted for ambient outdoor levels of particulate matter less than 2.5 μm.