Table 3

Self-reported symptoms from preworking, postworking and off-season questionnaires, and newly developed symptoms during the week in three occupational groups*

Occupational groupsPreworkingPostworkingP values†Off-seasonP values†Newly developed symptomsP values‡
(no/yes, %)(no/yes, %)(no/yes, %)(no/yes, %)OR (95% CI)‡
Lower airway symptoms
 Conventional asphalt workers91/25 (22)96/20 (17)0.3685/11 (11)0.077103/13 (11)0.74 (0.26 to 2.08)0.56
 CRM asphalt workers§38/9 (19)33/9 (21)0.7332/4 (11)0.6333/5 (13)1.89 (0.54 to 6.66)0.32
 Controls73/27 (27)83/15 (15)0.07963/10 (14)0.007488/10 (10)RefRef
Upper airway symptoms
 Conventional asphalt workers74/42 (36)70/46 (40)0.4862/34 (35)0.7097/19 (16)1.18 (0.50 to 2.75)0.71
 CRM asphalt workers§38/9 (19)32/10 (24)0.9923/13 (36)0.3030/8 (21)1.89 (0.66 to 5.39)0.24
 Controls59/41 (41)67/31 (32)0.1347/26 (36)0.2486/12 (12)RefRef
  • *Lower airway symptoms included wheezing, chest tightness, shortness of breath and cough; upper airway symptoms included eye symptoms (redness/secretion/swelling) and nasal symptoms (runny nose/nasal congestion/sneezing), as well as nasal bleeding. Newly developed symptoms were the symptoms with onset during the working week, that is, no report of such symptoms on the preworking questionnaire, but were reported on the postworking questionnaire.

  • †P values were derived from asymptotic McNemar test with preworking symptoms as the comparison group.

  • ‡OR and p values were derived from logistic regression adjusting for age, smoking history, cigarette pack-year and allergy.

  • §Four CRM asphalt workers did not report preworking symptoms. Nine CRM asphalt workers did not report postworking symptoms. Therefore, only 38 CRM asphalt workers were available to calculate newly developed symptoms.

  • CRM, crumb rubber modified; ref, reference.