Methodological issues in a prospective study on plasma concentrations of persistent organic pollutants and pancreatic cancer risk within the EPIC cohort by Gasull, M, Pumarega, J, Kiviranta, H, Rantakokko, P, Raaschou-Nielsen, O, Bergdahl, IA, Sandanger, TM, Goñi, F, Cirera, L, Donat-Vargas, C, Alguacil, J, Iglesias, M, Tjønneland, A, Overvad, K, Mancini, FR, Boutron-Ruault, M-C, Severi, G, Johnson, T, Kühn, T, Trichopoulou, A, Karakatsani, A, Peppa, E, Palli, D, Pala, V, Tumino, R, Naccarati, A, Panico, S, Verschuren, M, Vermeulen, R, Rylander, C, Nøst, TH, Rodríguez-Barranco, M, Molinuevo, A, Chirlaque, M-D, Ardanaz, E, Sund, M, Key, T, Ye, W, Jenab, M, Michaud, D, Matullo, G, Canzian, F, Kaaks, R, Nieters, A, Nöthlings, U, Jeurnink, S, Chajes, V, Matejcic, M, Gunter, M, Aune, D, Riboli, E, Agudo, A, Gonzalez, CA, Weiderpass, E, Bueno-De-Mesquita, B, Duell, EJ, Vineis, P, Porta, M