Abstract
PurposeBenzene is a known carcinogen for adult leukemia. Exposure to benzene through parental occupation and the use of household products has been associated with childhood leukemia (CL). Ambient benzene has also been associated with CL and central nervous system (CNS) tumors. We aimed to investigate whether the higher ambient levels of benzene in proximity of petrol stations are associated with a greater risk of childhood cancers, leukemia, and CNS tumors.MethodsWe identified children diagnosed with cancer at age 0–15 years during 1985–2015 from the Swiss Childhood Cancer Registry and selected 10 age and sex-matched controls per case from national censuses. We calculated the distance from children’s home to the nearest petrol station using precise geocodes. We estimated odds ratios using conditional logistic regression adjusting for ambient levels of NO2, distance to highways, level of urbanization, and presence of a cantonal cancer registry. In addition, we ran a meta-analysis pooling current results for CL with those of previous studies.ResultsWe identified 6129 cases, of which 1880 were leukemias and 1290 CNS tumors. 24 cases lived within 50 m from a petrol station. The adjusted odds ratio of a cancer diagnosis for children thus exposed compared to unexposed children (> 500 m) was 1.29 (0.84–1.98) for all cancers combined, 1.08 (0.46–2.51) for leukemia, and 1.30 (0.51–3.35) for CNS tumors. During 2000–2015, when exposure assessment was more precise, the adjusted odds ratio for any cancer diagnosis was 1.77 (1.05–2.98). The summary relative risk estimate for CL in the meta-analysis including four studies was 2.01 (1.25–3.22).ConclusionsOur study provides weak support for an increased risk of childhood cancers among children living close to petrol stations. A meta-analysis including our study suggests an increased risk for CL.
Highlights
Little is known about potential environmental risk factors of cancers in childhood
Benzene is a designated Group I carcinogen by the International Agency for Research on Cancer (IARC) and an established risk factor for acute myeloid leukemia in adults, with positive associations being noted for chronic myeloid leukemia and the broad category of nonHodgkin lymphoma (IARC 2017)
We considered confounding by the following factors: (1) outdoor air concentration level of NO2 as estimated by the national dispersion model PolluMap in 1990, 2000, and 2010 for a nationwide grid of cells of 200 × 200 m (Heldstab et al 2011); (2) traffic-related air pollution measured as the distance to the nearest highway (0– < 100, 100– < 250, 250– < 500, ≥ 500 m); (3) Swiss index of socio-economic position (SEP) of the immediate neighborhood area (Panczak et al 2012); and (4) degree of urbanization of the municipality of residence as defined by the Swiss Federal Office of Statistics
Summary
Little is known about potential environmental risk factors of cancers in childhood. The most common cancers affecting children in most world regions are leukemias and tumors of the central nervous system (CNS) (Steliarova-Foucher et al 2017). Benzene is a designated Group I carcinogen by the International Agency for Research on Cancer (IARC) and an established risk factor for acute myeloid leukemia in adults, with positive associations being noted for chronic myeloid leukemia and the broad category of nonHodgkin lymphoma (IARC 2017). There is growing evidence of an association between ambient levels of benzene at residence, especially as a component of traffic-related air pollution, and childhood leukemia, acute myeloid leukemia (Filippini et al 2019; Raaschou-Nielsen et al 2018). For childhood CNS tumors, several studies found a positive association with parental occupational exposure (Keegan et al 2013; Peters et al 2014), whereas the few studies on ambient exposure reported elevated risks only for some subtypes but not for others (Danysh et al 2015; Raaschou-Nielsen et al 2018; von Ehrenstein et al 2016)
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