Characteristics of the study participants in three occupational groups
| Conventional asphalt workers (n=116) | CRM asphalt workers (n=51) | Controls (n=100) | P values* | |
| Age | 43 (24–59) | 42 (22–61) | 46 (24–62) | 0.29 |
| BMI | 27.5 (22.4–38.2) | 27.8 (22.6–34.6) | 27.4 (22.2–35.4) | 0.89 |
| Years of asphalt work (years) | 12 (1–29) | 10 (1–38) | – | – |
| Self-reported COPD (no/yes, %)† | 114/0 (0) | 44/0 (0) | 99/1 (1) | 0.90 |
| Diagnosed asthma (no/yes, %)† | 106/8 (7) | 41/3 (7) | 87/13 (13) | 0.27 |
| Smoking history (never/ever/current, %)† | 84/24/6 (5) | 31/5/8 (18) | 65/23/12 (12) | 0.066 |
| Cigarette pack-year if ever smoker | 9 (2–30) | 18 (1–95) | 14 (1–54) | 0.083 |
| Snus history (never/ever/current, %)† | 54/15/45 (39) | 25/2/17 (39) | 66/13/21 (21) | 0.014 |
| Phadiatop allergy test (negative/positive, %)‡ | 72/41 (36) | 33/12 (27) | 62/34 (35) | 0.49 |
| Moulds (negative/positive, %) | 111/2 (2) | 45/0 (0) | 95/1 (1) | 0.61 |
| Mites (negative/positive, %) | 97/16 (14) | 41/4 (9) | 73/23 (24) | 0.049 |
| Animals (negative/positive, %) | 100/13 (12) | 43/2 (4) | 83/13 (14) | 0.27 |
| Pollen (negative/positive, %) | 76/37 (33) | 35/10 (22) | 73/23 (24) | 0.25 |
| Grass pollen (negative/positive, %) | 80/33 (29) | 35/10 (22) | 75/21 (22) | 0.44 |
| Total IgE‡ | 30.6 (3.5–291) | 30.9 (5.2–281) | 31.5 (3.5–279) | 0.87 |
Data presented as median (5th–95th percentiles) for continuous variables, and count (%) for categorical variables
*P values were derived from one-way analysis of variance for parametric continuous variables, and χ2 test or Fisher’s exact test for categorical variables with controls as the comparison group.
†Two conventional asphalt workers and seven CRM asphalt workers did not report disease history and smoking history on the preworking questionnaire.
‡Three conventional asphalt workers, six CRM asphalt workers and four controls did not give consent for blood sampling for allergy test.
BMI, body mass index; COPD, chronic obstructive pulmonary disease; CRM, crumb rubber modified.