Table 2.
Melamine concentrations and renal function indicators in different specimens in melamine tableware manufacturing workers by worksites and their comparison group
| Variables | Exposed Workers (n=44) | Nonexposed Workers Controls (N=105) | P valuea (Overall) | P valueb (Manufacturers versus Controls) | |||
|---|---|---|---|---|---|---|---|
| Manufacturers (N=16) | Grinders (N=8) | Packers (N=10) | Administrators (N=10) | ||||
| Mean±SD (median, IQR) | |||||||
| Exposure markers | |||||||
| Urine | |||||||
| Melamine (ng/ml) | 917.6±516.4 | 188.0±107.4 | 292.6±363.6 | 109.8±214.7 | 8.1±9.1 | <0.001 | <0.001 |
| (943.0, 438.0–1251.8) | (206.3, 64.7–291.6) | (252.6, 42.4–390.3) | (18.2, 12.6–101.3) | (4.3, 1.6–11.2)c | |||
| Melamine (μg/mmol Cr) | 84.4±47.4 | 18.4±9.7 | 24.2±23.0 | 4.6±6.8 | 0.7±0.9 | <0.001 | <0.001 |
| (80.5, 51.3–112.9) | (16.2, 12.3–29.5) | (15.9, 3.9–46.7) | (1.9, 1.0–5.2) | (0.3, 0.1–1.0)c | |||
| Serum | |||||||
| Melamine (ng/ml), N (%) | |||||||
| Non-detectabled | 0 | 5 (62.5) | 7 (70.0) | 7 (70.0) | — | <0.001 | |
| Detectable | 16 (100.0) | 3 (37.5) | 3 (30.0) | 3 (30.0) | — | ||
| 7.2±4.6 | 2.4±0.3 | 3.6±2.2 | 1.7±0.4 | — | |||
| (6.7, 4.0–9.6) | (2.4, 2.0–) | (2.4, 2.2–) | (1.6, 1.5–) | — | |||
| Nephrolithiasis markers | |||||||
| Urine | |||||||
| Microalbumin (mg/mmol Cr) | 14.8±49.2 | 1.0±0.6 | 0.8±0.5 | 1.5±2.7 | 1.9±6.8 | 0.486 | 0.248 |
| (0.8, 0.4–2.5) | (0.5, 0.5–1.7) | (0.7, 0.4–1.5) | (0.4, 0.3–1.5) | (0.6, 0.4–0.9) | |||
| NAG (IU/mmol Cr) | 1.8±3.5 | 0.9±0.8 | 0.6±0.4 | 0.6±0.3 | 0.4±0.2 | 0.002 | 0.002 |
| (0.9, 0.4–1.4) | (0.8, 0.3–0.9) | (0.5, 0.3–0.9) | (0.6, 0.3–0.9) | (0.4, 0.3–0.5) | |||
| β2-microglobulin, N (%) | |||||||
| Nondetectablee | 10 (62.5) | 6 (75.0) | 9 (90.0) | 9 (90.0) | 101 (96.2) | 0.006 | 0.007 |
| Detectable | 4 (25.0) | 1 (12.5) | 0 | 0 | 4 (3.8) | ||
| Missing | 2 (12.0) | 1 (12.5) | 1 (10.0) | 1 (10.0) | 0 | ||
| Laboratory data | |||||||
| eGFR | 83.4±14.0 | 81.0±12.1 | 82.7±8.2 | 80.0±10.1 | 77.8±9.7 | 0.383 | 0.246 |
| (79.6, 72.7–91.5) | (82.0, 70.9–88.1) | (86.0, 75.1–88.6) | (79.9, 73.3–88.5) | (77.4, 71.4–84.7) | |||
| eCCR | 80.8±12.0 | 78.9±14.0 | 82.0±15.4 | 98.1±35.4 | 78.4±13.2 | 0.518 | 0.375 |
| (79.7, 75.5–90.6) | (79.7, 68.0–86.7) | (79.3, 69.6–96.8) | (84.0, 73.6–117.9) | (77.6, 68.6–88.0) | |||
| eGFR<60 mL/min/1.73 m2, N (%) | 0 | 0 | 0 | 0 | 4 (3.8) | — | — |
| Urine, mg/dl | |||||||
| Creatinine | 142.9±64.1 | 123.1±60.2 | 140.7±52.0 | 185.2±92.2 | 143.7±78.3 | 0.706 | 0.843 |
| (139.4, 81.0–202.7) | (112.9, 95.7–145.3) | (139.5, 87.2–181.7) | (150.9, 116.1–276.8) | (124.9, 83.0–202.9) | |||
| Serum, mg/dl | |||||||
| BUN | 15.1±4.6 | 14.0±3.1 | 13.2±3.2 | 14.1±3.6 | 13.1±2.7f | 0.541 | 0.141 |
| (15.4, 11.5–18.1) | (14.0, 11.7–16.9) | (12.6, 10.9–15.6) | (13.6, 11.8–17.8) | (13.0, 10.7–14.8) | |||
| Creatinine | 1.0±0.2 | 0.9±0.2 | 0.9±0.1 | 1.0±0.1 | 1.1±0.1f | <0.001 | 0.116 |
| (1.0, 0.8–1.1) | (0.9, 0.8–1.0) | (0.9, 0.8–1.0) | (1.0, 0.9–1.0) | (1.1, 1.0–1.1) | |||
| Uric acid | 5.7±1.6 | 5.7±2.6 | 5.1±1.4 | 6.8±1.2 | 6.0±1.3f | 0.061 | 0.162 |
| (5.6, 4.4–6.5) | (5.4, 3.7–7.6) | (5.1, 4.0–6.1) | (6.6, 5.6–8.0) | (5.9, 5.1–7.0) | |||
IQR, interquartile range; Cr, creatinine; eGFR, estimated glomerular filtration rate calculated by the Modification of Diet in Renal Disease calculator-extended version (adjusted by age, gender, serum creatinine, and race), unit as ml/min/1.73 m2; eCCr, estimated creatinine clearance rate calculated by the Modification of the Cockcroft–Gault Calculator (adjusted by age, gender, serum creatinine, and weight), unit as ml/min.
Kruskal–Wallis test or chi-squared test.
Wilcoxon rank-sum test or Fisher’s exact test.
n=42.
MDL of melamine in serum: 1.33 ng/ml.
MDL for β2-microglobulin: 0.206 mg/l.
Missing data, n=2.