title: Resolving uncertainty in the spatial relationships between passive benzene exposure and risk of non-Hodgkin lymphoma.
abstract: BACKGROUND
  Benzene is a known occupational carcinogen associated with increased risk of hematologic cancers, but the relationships between quantity of passive benzene exposure through residential proximity to toxic release sites, duration of exposure, lag time from exposure to cancer development, and lymphoma risk remain unclear.
  
  
  METHODS
  We collected release data through the Environmental Protection Agency's Toxics Release Inventory (TRI) from 1989 to 2003, which included location of benzene release sites, years when release occurred, and amount of release. We also collected data on incident cases of non-Hodgkin lymphoma (NHL) from the Georgia Comprehensive Cancer Registry (GCCR) for the years 1999-2008. We constructed distance-decay surrogate exposure metrics and Poisson and negative binomial regression models of NHL incidence to quantify associations between passive exposure to benzene and NHL risk and examined the impact of amount, duration of exposure, and lag time on cancer development. Akaike's information criteria (AIC) were used to determine the scaling factors for benzene dispersion and exposure periods that best predicted NHL risk.
  
  
  RESULTS
  Using a range of scaling factors and exposure periods, we found that increased levels of passive benzene exposure were associated with higher risk of NHL. The best fitting model, with a scaling factor of 4 kilometers (km) and exposure period of 1989-1993, showed that higher exposure levels were associated with increased NHL risk (Level 4 (1.1-160kilograms (kg)) vs. Level 1: risk ratio 1.56 [1.44-1.68], Level 5 (>160kg) vs. Level 1: 1.60 [1.48-1.74]).
  
  
  CONCLUSIONS
  Higher levels of passive benzene exposure are associated with increased NHL risk across various lag periods. Additional epidemiological studies are needed to refine these models and better quantify the expected total passive benzene exposure in areas surrounding release sites.
authors.affiliation: Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA. Electronic address: jswitch@emory.edu.
authors.forename: Jeffrey M
authors.initials: JM
authors.lastname: Switchenko
authors.affiliation: Department of Hematology and Oncology, Winship Cancer Institute, Emory University, Atlanta, GA, USA.
authors.forename: Catherine
authors.initials: C
authors.lastname: Bulka
authors.affiliation: Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, GA, USA; Georgia Center for Cancer Statistics, Atlanta, GA, USA.
authors.forename: Kevin
authors.initials: K
authors.lastname: Ward
authors.affiliation: Department of Hematology and Oncology, Winship Cancer Institute, Emory University, Atlanta, GA, USA.
authors.forename: Jean L
authors.initials: JL
authors.lastname: Koff
authors.affiliation: Georgia Department of Public Health, Atlanta, GA, USA.
authors.forename: A Rana
authors.initials: AR
authors.lastname: Bayakly
authors.affiliation: Department of Environmental Health, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
authors.forename: P Barry
authors.initials: PB
authors.lastname: Ryan
authors.affiliation: Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, Atlanta, GA, USA.
authors.forename: Lance A
authors.initials: LA
authors.lastname: Waller
authors.affiliation: Department of Hematology and Oncology, Winship Cancer Institute, Emory University, Atlanta, GA, USA.
authors.forename: Christopher R
authors.initials: CR
authors.lastname: Flowers
mesh_terms: D001554:Benzene / Q000633:toxicity*; D005845:Georgia; D006801:Humans; D015994:Incidence; D008228:Lymphoma, Non-Hodgkin / Q000453:epidemiology*; D016017:Odds Ratio; D012306:Risk; D035501:Uncertainty
chemical_list: D001554:Benzene
keywords: EPA; Environmental epidemiology; Lymphoma; Spatial epidemiology; Toxic release sites