Background There is a controversy on exposure and adverse health effects of workers working with road asphalt paving. Furthermore, the increasing usage of crumb rubber modified (CRM) asphalt raises the concern of exposure to CRM asphalt.
Objective To assess the exposure of both conventional and CRM asphalt, and to elucidate the health effects regarding airway symptoms, lung function, inflammation response and genotoxic effects on telomere length (TL) and mitochondria DNA copy number (mtDNAcn).
Methods We carried out a cross-week study with 116 workers with conventional asphalt, 51 workers with CRM asphalt and 100 controls in Sweden. Personal air sampling was carried out in 60 workers in varied worksites. Symptoms during working week were investigated by standard questionnaires. Lung function test results together with urine and blood samples were collected before work on Monday morning and immediately after work on Thursday afternoon.
Results The exposure level for benzothiazol was higher in CRM asphalt (2.2 ± 0.8 µg/m3) than conventional asphalt (0.7 ± 0.8 µg/m3, p < 0.001). Urinary 1-hydroxypyrene on Thursday afternoon increased 1.75-fold in conventional asphalt workers (0.04 to 0.07 μmol/mol creatinine, p < 0.001), and 2.75-fold in CRM asphalt workers (0.06 to 0.11 μmol/mol creatinine, p < 0.001) compared to Monday morning. No difference was found regarding symptoms, lung function, CRP and TL between workers and controls, but workers showed higher mtDNAcn than controls (β = 0.14, p < 0.001 for conventional asphalt workers, β = 0.074, p = 0.09 for CRM asphalt workers).
Conclusion The results do not indicate that road asphalt paving in open area is an occupation with high exposure or severe health issues. Similarly, the results do not suggest that CRM asphalt is related to more adverse health effects than conventional asphalt. However, the higher concentration of benzothiazole during CRM paving may suggest that crumb rubber is a main source and that benzothiazole may be useful as an indicator of CRM fume exposure.
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