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Table 2 Description of joint exposures

From: Adult asthma and traffic exposure at residential address, workplace address, and self-reported daily time outdoor in traffic: A two-stage case-control study

The 2nd survey   NOx at workplace address (μg/m3) Time outdoor in traffic/day (self-reported)  
   total 0-8 8-11 11-14 14-19 > 19 Total 0-30 min 30-1 h 1-2 h > 2 h
NOx at residential address (μg/m3) 0-8 770 412(53.5%) 78(10.1%) 132(17.1%) 60(7.8%) 88(11.4%) 770 159(20.6%) 306(39.7%) 188(24.4%) 117(15.2%)
  8-11 210 30(14.3%) 44(21.0%) 59(28.1%) 32(15.2%) 45(21.4%) 210 34(16.2%) 87(41.4%) 55(26.2%) 34(16.2%)
  11-14 210 13(6.2%) 15(7.1%) 102(48.6%) 26(12.4%) 54(25.7%) 210 41(19.5%) 88(41.9%) 65(31.0%) 16(7.6%)
  14-19 161 4(2.5%) 7(4.3%) 38(23.6%) 39(24.2%) 73(45.3%) 161 29(18.0%) 65(40.4%) 41(25.5%) 26(16.1%)
  > 19 137 9(6.6%) 4(2.9%) 18(13.1%) 26(19.0%) 80(58.4%) 137 20(14.6%) 53(38.7%) 37(27.0%) 27(19.7%)
  1. Percentage within row total. Exposure to residential traffic was predictive of exposure at workplace address, but less predictive of time spent outdoor in traffic. The first row shows that of those who live at a residential address with 0-8 ug NOx/m3, 53.5% also have a workplace address with 0-8 ug NOx/m3 and 20.6% spend 0-30 min outdoor in traffic/day.