title: Invited commentary: in defense of ecologic studies for testing a linear-no threshold theory.
authors.affiliation: Department of Physics and Astronomy, University of Pittsburgh, PA 15260.
authors.forename: B L
authors.initials: BL
authors.lastname: Cohen
mesh_terms: D015982:Bias; D015986:Confounding Factors, Epidemiologic; D004463:Ecology; D004812:Epidemiologic Methods; D006801:Humans; D016014:Linear Models; D008452:Maximum Allowable Concentration; D015203:Reproducibility of Results; D012307:Risk Factors