Cancer
Parental employment in bitumen-related industries in relation to childhood cancer risk Julia Heck* Julia Heck Chisom Iwundu Beate Ritz Johnni Hansen
Objective: Occupational exposure to bitumen used for roofing is classified by IARC as “probably carcinogenic to humans” (Group 2A), while bitumen used for road paving is classified as “possibly carcinogenic” (Group 2B). Further, coal tar previously used for paving is classified as “carcinogenic to humans” (Group 1). Despite these classifications, there are limited studies on childhood cancer in the offspring of workers exposed to bitumen.
Material and Methods: Our case-control study utilized data from Danish national registers. Cases (1968-2016) were identified from the Cancer Registry and linked to their parents via the Central Person Register. Occupational exposures were identified from the Supplementary Pension Fund Register with compulsory membership for all employees since 1964, which identifies the type and dates of every job. Conditional logistic regression was used to estimate the risk of pediatric cancers in offspring of fathers employed in bitumen-exposed and coal tar industries in the year preconception or during the pregnancy, and of mothers employed at any time in life.
Results: Combining all cancer types, paternal employment in bitumen-exposed industries during preconception or during the index pregnancy [Odds Ratio (OR)=1.05, 95% Confidence Interval (CI)=0.95-1.16] or employment at any time prior to the child’s cancer diagnosis (OR=1.04, 95% CI=0.98-1.11), were not related to pediatric cancer risk. With regards to specific cancer types, an increased risk was indicated for astrocytoma with paternal bitumen-related employment in the perinatal period (OR=1.64, 95% CI=0.98-2.73; N=17 exposed cases). Maternal employment prior to the child’s cancer diagnosis (OR=1.22, 95% CI=1.03-1.44; N=151 exposed cases) was related to increased pediatric cancer risk (all cancer types combined) and to ependymoma (OR=3.55, 95% CI 1.57-8.05; N=7 exposed cases) and rhabdomyosarcoma (OR=3.83, 95%CI 1.85-7.96; N=9 exposed cases).
Conclusion: Although the small sample sizes must be taken into account, elevated risk for pediatric cancers may occur with parental occupational exposure to bitumen. However, additional exposure to coal tars cannot be excluded.