Tackling second-hand exposure to tobacco smoke and aerosols of electronic cigarettes: the TackSHS project protocol Esteve Fernández; María José López; Silvano Gallus; Sean Semple; Luke Clancy; Panagiotis Behrakis; Ario Ruprecht; Giuseppe Gorini; Ángel López-Nicolás; Cornel Radu-Loghin; Joan B. Soriano;