Preterm birth, small for gestational age, and major malformations for exposures to different substances, according to an external exposure matrix, among laboratory technicians (n = 991)
| Exposure index* | Births, n | Preterm birth | Small for gestational age | “Major” malformations | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| n (%) | Crude OR | Adjusted OR (95% CI) | n (%) | Crude OR | Adjusted OR (95% CI) | n (%) | Crude HR | Adjusted HR (95% CI) | ||
| Cox regression for major malformations, HR: hazard ratio; logistic regression for preterm birth and small for gestational age, OR: odds ratio; adjusted for maternal age, gravidity, history of spontaneous abortion, prepregnancy body mass index, smoking, alcohol consumption, paternal job, and sex of child; CI: confidence interval; reference group for exposure to each substance was laboratory technicians not exposed to the particular substance; numbers for each exposure may not add to n = 991 due to missing; tests for trend: p = 0.256–0.888 for all the outcomes in relation to the exposures, except for p = 0.047 for major malformations in relation to exposure to experimental animals. | ||||||||||
| *An exposure index (EI) for each exposure was calculated as follows: EI = EL×F, where EL = exposure level (see Zhu et al19), low = 1, medium = 2, and high = 3; F = frequency of work contacts, every day = 4, several times per week = 3, several days per month = 2, and more rare = 1. It was then grouped into 1–5 and 6+. | ||||||||||
| Experimental animals | ||||||||||
| 0 | 687 | 28 (4.1) | 1.0 | 1.0 | 53 (7.8) | 1.0 | 1.0 | 33 (4.8) | 1.0 | 1.0 |
| 1–5 | 234 | 10 (4.3) | 1.1 | 1.0 (0.5 to 2.2) | 20 (8.5) | 1.1 | 1.2 (0.7 to 2.0) | 17 (7.3) | 1.5 | 1.5 (0.8 to 2.7) |
| 6+ | 61 | 1 (1.6) | 0.4 | 0.3 (0.0 to 2.7) | 7 (11.7) | 1.6 | 1.6 (0.7 to 3.7) | 6 (9.8) | 2.1 | 2.2 (0.9 to 5.2) |
| Epoxy substances | ||||||||||
| 0 | 774 | 33 (4.3) | 1.0 | 1.0 | 59 (7.7) | 1.0 | 1.0 | 41 (5.3) | 1.0 | 1.0 |
| 1–5 | 76 | 0 (0.0) | NA | NA | 8 (10.5) | 1.4 | 1.6 (0.7 to 3.5) | 6 (7.9) | 1.5 | 1.4 (0.6 to 3.4) |
| 6+ | 136 | 6 (4.4) | 1.0 | 0.9 (0.4 to 2.4) | 13 (9.6) | 1.3 | 1.2 (0.6 to 2.4) | 9 (6.6) | 1.2 | 1.3 (0.6 to 2.6) |
| Formaldehyde | ||||||||||
| 0 | 401 | 18 (4.5) | 1.0 | 1.0 | 30 (7.6) | 1.0 | 1.0 | 20 (5.0) | 1.0 | 1.0 |
| 1–5 | 364 | 14 (3.8) | 0.9 | 1.0 (0.5 to 2.0) | 31 (8.7) | 1.2 | 1.2 (0.7 to 2.0) | 20 (5.5) | 1.1 | 1.2 (0.6 to 2.1) |
| 6+ | 218 | 7 (3.2) | 0.7 | 0.7 (0.3 to 1.7) | 19 (8.7) | 1.2 | 1.2 (0.6 to 2.2) | 16 (7.3) | 1.5 | 1.5 (0.8 to 2.9) |
| Dyes | ||||||||||
| 0 | 257 | 12 (4.7) | 1.0 | 1.0 | 23 (9.1) | 1.0 | 1.0 | 20 (7.8) | 1.0 | 1.0 |
| 1–5 | 303 | 13 (4.3) | 0.9 | 0.8 (0.3 to 1.8) | 18 (6.0) | 0.6 | 0.6 (0.3 to 1.2) | 12 (4.0) | 0.5 | 0.5 (0.2 to 1.0) |
| 6+ | 406 | 14 (3.4) | 0.7 | 0.7 (0.3 to 1.5) | 37 (9.2) | 1.0 | 1.0 (0.6 to 1.7) | 23 (5.7) | 0.7 | 0.7 (0.4 to 1.3) |
| Radioisotopes | ||||||||||
| 0 | 426 | 20 (4.7) | 1.0 | 1.0 | 34 (8.1) | 1.0 | 1.0 | 27 (6.3) | 1.0 | 1.0 |
| 1–5 | 354 | 11 (3.1) | 0.7 | 0.6 (0.3 to 1.4) | 25 (7.1) | 0.9 | 0.8 (0.5 to 1.5) | 15 (4.2) | 0.7 | 0.7 (0.4 to 1.3) |
| 6+ | 199 | 10 (5.0) | 1.1 | 1.0 (0.5 to 2.3) | 20 (10.2) | 1.3 | 1.2 (0.7 to 2.2) | 13 (6.5) | 1.0 | 1.0 (0.5 to 2.0) |
| Heavy metals | ||||||||||
| 0 | 699 | 31 (4.4) | 1.0 | 1.0 | 59 (8.6) | 1.0 | 1.0 | 40 (5.7) | 1.0 | 1.0 |
| 1–5 | 103 | 5 (4.9) | 1.1 | 1.0 (0.4 to 2.6) | 5 (4.9) | 0.5 | 0.5 (0.2 to 1.3) | 7 (6.8) | 1.2 | 1.2 (0.5 to 2.7) |
| 6+ | 174 | 5 (2.9) | 0.6 | 0.6 (0.2 to 1.6) | 16 (9.2) | 1.1 | 1.2 (0.6 to 2.1) | 9 (5.2) | 0.9 | 0.8 (0.4 to 1.7) |
| Organic solvents | ||||||||||
| 0 | 129 | 4 (3.1) | 1.0 | 1.0 | 11 (8.5) | 1.0 | 1.0 | 4 (3.1) | 1.0 | 1.0 |
| 1–5 | 176 | 9 (5.1) | 1.7 | 1.7 (0.5 to 6.0) | 12 (7.0) | 0.8 | 0.9 (0.4 to 2.1) | 11 (6.3) | 2.0 | 2.1 (0.7 to 6.5) |
| 6+ | 641 | 25 (3.9) | 1.3 | 1.3 (0.4 to 3.9) | 55 (8.7) | 1.0 | 1.0 (0.5 to 2.0) | 39 (6.1) | 2.0 | 2.0 (0.7 to 5.7) |