Table 2 Crude and adjusted ORs for PTB (< 37 weeks’ gestation) based on tract-level metal concentrations in private wells
From: Toxic metal mixtures in private well water and increased risk for preterm birth in North Carolina
Metal | ppb | Non-cases | Cases | Crude OR (95% CI) | Adjusted* OR (95% CI) |
|---|---|---|---|---|---|
Arsenic | |||||
 <  = 50th perc | 0.220 | 609,926 | 55,433 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 487,868 | 43,709 | 0.99 (0.97,1.00) | 0.98 (0.97,1.00) |
 >  = 90th perc | 2.838 | 121,378 | 10,757 | 0.98 (0.95,1.00) | 0.97 (0.94,0.99) |
 tract with < 25% of tests >  = EPA standard | Standard=10 | 1,197,886 | 21,286 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 107,999 | 1900 | 0.99 (0.94,1.04) | 0.97 (0.92,1.02) |
Cadmium | |||||
 <  = 50th perc | 0.007 | 609,466 | 55,164 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 488,279 | 43,653 | 0.99 (0.98,1.00) | 1.02 (1.00,1.04) |
 >  = 90th perc | 0.127 | 121,427 | 11,082 | 1.01 (0.99,1.03) | 1.02 (0.99,1.05) |
 tract with < 25% of tests >  = EPA standard | Standard=5 | 1,214,353 | 4819 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 109,433 | 466 | 1.07 (0.97,1.18) | 1.11 (1.00,1.23) |
Chromium | |||||
 <  = 50th perc | 0.579 | 608,834 | 55,735 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 488,409 | 43,538 | 0.97 (0.96,0.99) | 1.02 (1.00,1.03) |
 >  = 90th perc | 2.872 | 121,929 | 10,626 | 0.95 (0.93,0.97) | 0.99 (0.97,1.02) |
 tract with < 25% of tests >  = EPA standard | Standard= 100 | 1,214,353 | 435 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 109,850 | 49 | 1.25 (0.92,1.66) | 1.06 (0.77,1.43) |
Copper | |||||
 <  = 50th perc | 21.096 | 608,590 | 56,031 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 488,791 | 43,089 | 0.96 (0.95,0.97) | 1.01 (0.99,1.03) |
 >  = 90th perc | 141.545 | 121,791 | 10,779 | 0.96 (0.94,0.98) | 0.98 (0.95,1.01) |
 tract with < 25% of tests >  = EPA standard | Standard = 1300 | 1,214,840 | 4332 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 109,510 | 389 | 1.00 (0.90,1.10) | 0.52 (0.13,1.34) |
Lead | |||||
 <  = 50th perc | 1.433 | 609,888 | 54,784 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 487,904 | 43,740 | 1.00 (0.99,1.01) | 1.01 (1.00,1.03) |
 >  = 90th perc | 9.104 | 121,380 | 11,375 | 1.04 (1.02,1.06) | 1.04 (1.02,1.07) |
 tract with < 25% of tests >  = EPA standard | Standard= 15 | 1,191,607 | 27,565 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 107,257 | 2642 | 1.07 (1.02,1.11) | 1.10 (1.02,1.18) |
Manganese | |||||
 <  = 50th perc | 33.626 | 609,411 | 55,515 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 488,057 | 43,761 | 0.98 (0.97,1.00) | 0.99 (0.97,1.00) |
 >  = 90th perc | 188.923 | 121,704 | 10,623 | 0.96 (0.94,0.98) | 0.98 (0.95,1.00) |
 tract with < 25% of tests >  = EPA standard | Standard= 300 | 1,176,657 | 42,515 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 106,221 | 3678 | 0.96 (0.93,0.99) | 0.96 (0.92,1.01) |
Zinc | |||||
 <  = 50th perc | 126.764 | 608,922 | 55,763 | 1.00 (ref.) | 1.00 (ref.) |
 > 50th perc to < 90th perc |  | 487,844 | 43,642 | 0.98 (0.96,0.99) | 1.01 (0.99,1.02) |
 >  = 90th perc | 1592.883 | 122,406 | 10,494 | 0.94 (0.92,0.96) | 0.95 (0.92,0.97) |
 tract with < 25% of tests >  = EPA standard | Standard= 5000 | 1,210,117 | 9055 | 1.00 (ref.) | 1.00 (ref.) |
 tract with >  = 25% of tests >  = EPA standard |  | 109,200 | 699 | 0.86 (0.79,0.92) | 0.77 (0.56,1.02) |