|  |   Model 1: Unadjusted GEE |  |   Model 2: Multivariable GEEb |  |
---|---|---|---|---|---|
 | Events/N | RR | 95% CI | RR | 95% CI |
Exposure categorized by any or the sample median | Â | Â | Â | Â | Â |
  Any exposure | 92/1,091 | 0.81 | 0.61, 1.07 | 0.86 | 0.65, 1.14 |
  ≥50th (5.7 × 10-1 g - 89.2 g) | 55/635 | 0.82 | 0.59, 1.14 | 0.90 | 0.65, 1.24 |
  >0- < 50th (1.2 × 10-4 g – 5.7 × 10-1 g) | 37/456 | 0.79 | 0.54, 1.15 | 0.82 | 0.55, 1.23 |
  0 | 104/1,019 | 1.00 | Referent | 1.00 | Referent |
Exposure categorized by 1980 action level (40Â ppb) | Â | Â | Â | Â | Â |
  ≥1.136 g (40 ppb) | 39/480 | 0.77 | 0.54, 1.11 | 0.88 | 0.62, 1.26 |
  >0 - <1.136 g | 53/611 | 0.83 | 0.60, 1.16 | 0.85 | 0.61, 1.20 |
  0 | 104/1,019 | 1.00 | Referent | 1.00 | Referent |
Exposure categorized in quartiles (percentiles) | Â | Â | Â | Â | Â |
  ≥75th (2.3 g - 89.2 g) | 26/331 | 0.77 | 0.50, 1.17 | 0.87 | 0.56, 1.35 |
  50th-75th (5.7 × 10-1 g - 2.3 g) | 29/304 | 0.88 | 0.57, 1.35 | 0.91 | 0.60, 1.39 |
  25th-50th (1.3 × 10-1 g - 5.7 × 10-1 g) | 20/261 | 0.72 | 0.44, 1.18 | 0.74 | 0.43, 1.26 |
  >0- < 25th (1.2 × 10-4 g – 1.3 × 10-1 g) | 17/195 | 0.89 | 0.54, 1.46 | 0.95 | 0.58, 1.54 |
  0 | 104/1,019 | 1.00 | Referent | 1.00 | Referent |