Des fumées et leur écran. Éteindre les polémiques au sujet des rejets industriels de fluor et de mercure dans les Alpes suisses (1900–1950)

This article explores two cases of industrial pollution that affected the canton of Valais from 1910 to the present day. Driven by hydroelectricity, this agricultural canton entered industrial modernity in the space of two generations and discovered its externalities with fluoride and mercury residues that ravaged crops and made workers, residents and their livestock suffer. The article shows how a small world of experts favourable to the aluminium (AIAG) and carbochemistry (Lonza) industries was set up that first dismissed the lay knowledge denouncing pollution as superstitious, then contradicted Prof. Hector Cristiani’s discoveries about industrial fluorosis, and finally controlled the technical choices made in water purification. A community of interests developed between a few recognised experts (Heinrich Zangger, Louis Michaud, Maurice Vouga) and the companies, leading to the imposition of compensation for damages as the standard regulation for the victims of pollution.