Table 1. Sum and Individual PCBs with Largest Change from Year 1 to Year 2a.
| PCB | change in concentration (fifth to 95th) | % change (fifth to 95th) | estimated % change due to analytical variability | % mothers, with Δ > analytical variability | % children with Δ > analytical variability |
|---|---|---|---|---|---|
| 20 + 28 | –6 to 5 | –32 to 29 | 87 | 10 | 3 |
| 66 | –5 to 8 | –13 to 66 | 136 | 1 | 1 |
| 83 + 99 | –9 to 7 | –85 to 58 | –2 | 85 | 64 |
| 105 | –3 to 5 | –20 to 46 | 58 | 10 | 1 |
| 110 + 115 | –8 to 12 | –26 to 39 | N/A | N/A | N/A |
| 118 | –10 to 13 | –57 to 99 | 8 | 71 | 29 |
| 129 + 137 + 138 + 163 + 164 | –7 to 9 | –71 to 69 | –14 | 44 | 21 |
| 146 | 0 to 3 | 0 to 61 | 50 | 8 | 2 |
| 153 + 168 | –6 to 9 | –75 to 60 | –8 | 49 | 31 |
| 156 + 157 | 0 to 4 | 0 to 53 | –1 | 60 | 8 |
| 170 | –2 to 5 | –18 to 69 | –13 | 35 | 4 |
| 180 + 193 | –3 to 7 | –30 to 93 | 4 | 71 | 32 |
| 187 | –3 to 4 | –22 to 46 | 1 | 81 | 25 |
| ΣPCBs | –50 to 83 | –87 to 567 | 22 | 76 | 88 |
Note: Concentration is in units of ng/g lipid weight. The estimated % change due to analytical variability was determined from extraction and analysis of NIST SRM 1957 in both year 1 and year 2, where N/A means not available because congener concentrations are not certified by NIST. The 10 coeluting groups (containing 19 congeners) with biggest decrease in concentration (as indicated by the 5th percentile of the difference between year 1 and year 2) and 10 coeluting groups (containing 18 congeners) with the biggest increase in concentration (as indicated by the 95th percentile of the difference between year 1 and year 2) were selected for this table. Seven coeluting groups (containing 14 congeners) had both the biggest decrease and biggest increase).