Table 3

Spearman correlation coefficients (rs) between environmental markers and biomarkers of secondhand smoke (presented as rs and p-value)

PM2.5Air nicotineCOPlasma cotinine*Urine cotinine*Urine COT+3HC*Urine NNAL*
PM2.51.00−0.09 (0.9)0.77 (0.07)0.94 (0.005)0.31 (0.5)0.43 (0.4)0.60 (0.2)
Air nicotine1.00−0.07 (0.9)0.02 (0.9)0.55 (0.1)0.48 (0.2)0.52 (0.2)
CO1.000.76 (0.028)0.39 (0.4)0.45 (0.3)0.36 (0.4)
Plasma cotinine1.000.67 (0.07)0.74 (0.037)0 (1.0)
Urine cotinine1.000.95 (<0.001)0.24 (0.6)
Urine COT+3HC1.000.14 (0.7)
Urine NNAL1.00
  • *Maximum concentration minus baseline concentration.

  • Correlations in bold are significant (p<0.05).

  • *Maximum concentration minus baseline concentration.

  • CO, carbon monoxide; COT + 3HC combined cotinine and 3-hydroxycotinine; NNAL, 4-(methylnitrosoamino)-(3-pyridyl)1-butanol; PM2.5, particulate matter ≤2.5 μm.