. 2016 Aug 22;21(4):e37585. doi: 10.5812/traumamon.37585

Table 3. Results of crude and adjusted negative binomial regression, and the effects of pollutants and weather variables on traffic crashes (ratio of increase in traffic crashes per month to unit of increase in pollutants and weather variables per month on average).

Variables	Crude IRR* and 95% CI	P	Adjusted IRR* and 95% CI	P
O ₃ (ppm)	0.99825 (0.99746 - 0.99903)	< 0.001^a	0.99884 (0.99806 - 0.99961)	0.004^a
PM ₁₀ (µg/m ³ )	1.00124 (1.00032 - 1.00217)	0.008^a	0.99974 (0.99895 - 1.00052)	0.519
NO (ppm)	0.97420 (0.967008 - 0.98145)	< 0.001^a	0.99452 (0.98308 - 1.0060)	0.352
NO ₂ (ppm)	0.98062 (0.97444 - 0.98683)	< 0.001^a	0.98929 (0.9803171 - 0.9983392)	0.020^a
NO _x (ppm)	0.98698 (0.98270 - 0.99128)	< 0.001^a	0.99264 (0.98807 - 0.99722)	0.002^a
CO (ppm)	1.00003 (0.99994 - 1.00011)	0.483	0.99996 (0.99990 - 1.00002)	0.267
SO ₂ (ppm)	0.99746 (0.9910563 - 1.003902)	0.439	0.99725 (0.99229 - 1.00223)	0.280
Temperature (°C)	1.01213 (0.99967 - 1.02475)	0.040^a	1.02910 (1.01010 - 1.06745)	0.044^a
Relative humidity (%)	0.98939 (0.98283 - 0.99598)	0.002^a	0.97280(0.95550 - 0.99041)	0.003^a
Total evaporation(mm)	1.00047 (0.99976 - 1.00118)	0.192	0.99759 (0.99545 - 0.99973)	0.027^a
Sunny days (number in month)	0.99961 (0.99765 - 1.00156)	0.696	0.99646 (0.99295 - 0.99998)	0.040^a
Rainy days (number in month)	0.99696 (0.99239 - 1.00155)	0.195	1.00312 (1. 00112 - 1.00799)	0.043^a
Frost days (number in month)	1.17526 (1.12526 - 2.46156)	0.004^a	1.09876 (1.05877 - 1.92172)	0.021^a
Wind speed (m/s)	1.01331 (0.99186 - 1.03523)	0.226	1.00088 (0.98520 - 1.01680)	0.913

Abbreviation: IRR, incidence rate ratio.

^aStatistically significant.