title: Distance to high-voltage power lines and risk of childhood leukemia--an analysis of confounding by and interaction with other potential risk factors.
abstract: We investigated whether there is an interaction between distance from residence at birth to nearest power line and domestic radon and traffic-related air pollution, respectively, in relation to childhood leukemia risk. Further, we investigated whether adjusting for potential confounders alters the association between distance to nearest power line and childhood leukemia. We included 1024 cases aged <15, diagnosed with leukemia during 1968-1991, from the Danish Cancer Registry and 2048 controls randomly selected from the Danish childhood population and individually matched by gender and year of birth. We used geographical information systems to determine the distance between residence at birth and the nearest 132-400 kV overhead power line. Concentrations of domestic radon and traffic-related air pollution (NOx at the front door) were estimated using validated models. We found a statistically significant interaction between distance to nearest power line and domestic radon regarding risk of childhood leukemia (p = 0.01) when using the median radon level as cut-off point but not when using the 75th percentile (p = 0.90). We found no evidence of an interaction between distance to nearest power line and traffic-related air pollution (p = 0.73). We found almost no change in the estimated association between distance to power line and risk of childhood leukemia when adjusting for socioeconomic status of the municipality, urbanization, maternal age, birth order, domestic radon and traffic-related air pollution. The statistically significant interaction between distance to nearest power line and domestic radon was based on few exposed cases and controls and sensitive to the choice of exposure categorization and might, therefore, be due to chance.
authors.affiliation: Danish Cancer Society Research Center, Copenhagen Ø, Denmark.
authors.forename: Camilla
authors.initials: C
authors.lastname: Pedersen
authors.affiliation: Danish Cancer Society Research Center, Copenhagen Ø, Denmark; Danish Building Research Institute, Aalborg University, Construction and Health, Copenhagen SV, Denmark.
authors.forename: Elvira V
authors.initials: EV
authors.lastname: Bräuner
authors.affiliation: Social Medicine Section, Department of Public Health, University of Copenhagen, Copenhagen K, Denmark.
authors.forename: Naja H
authors.initials: NH
authors.lastname: Rod
authors.affiliation: Danish Cancer Society Research Center, Copenhagen Ø, Denmark.
authors.forename: Vanna
authors.initials: V
authors.lastname: Albieri
authors.affiliation: Risø National Laboratory for Sustainable Energy, Radiation Research Division, Technical University of Denmark, Roskilde, Denmark.
authors.forename: Claus E
authors.initials: CE
authors.lastname: Andersen
authors.affiliation: National Institute of Radiation Protection, Herlev, Denmark.
authors.forename: Kaare
authors.initials: K
authors.lastname: Ulbak
authors.affiliation: Department of Environmental Science, Aarhus University, Roskilde, Denmark; Department for Environmental, Social and Spatial Change (ENSPAC), Roskilde University, Roskilde, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Hertel
authors.affiliation: Danish Cancer Society Research Center, Copenhagen Ø, Denmark; Oncology Clinic, Finsen Centre, Rigshospitalet 5073, University of Copenhagen, Copenhagen Ø, Denmark.
authors.forename: Christoffer
authors.initials: C
authors.lastname: Johansen
authors.affiliation: International Agency for Research on Cancer (IARC), Section of Environment and Radiation, Lyon, France.
authors.forename: Joachim
authors.initials: J
authors.lastname: Schüz
authors.affiliation: Danish Cancer Society Research Center, Copenhagen Ø, Denmark.
authors.forename: Ole
authors.initials: O
authors.lastname: Raaschou-Nielsen
mesh_terms: D000293:Adolescent; D000367:Age Factors; D000393:Air Pollutants / Q000009:adverse effects; D000397:Air Pollution / Q000009:adverse effects; D016022:Case-Control Studies; D002648:Child; D002675:Child, Preschool; D015986:Confounding Factors, Epidemiologic; D003718:Denmark / Q000453:epidemiology; D004559:Electric Wiring / Q000009:adverse effects*; D004781:Environmental Exposure / Q000009:adverse effects*; D006801:Humans; D007223:Infant; D007938:Leukemia / Q000453:epidemiology / Q000209:etiology*; D016017:Odds Ratio; D011886:Radon / Q000009:adverse effects; D012042:Registries; D012111:Residence Characteristics; D012306:Risk; D012307:Risk Factors
chemical_list: D000393:Air Pollutants; D011886:Radon