The aim of this study was to assess to which extent the modernisation of an anode plant had reduced occupational chemical health hazards for jobs with the highest potential of exposure. Periodical measurements of dust and gases were performed at the same workplaces using the same methods, before and after modernisation. These measurements were compared with the recommended standards. Before modernisation the concentrations of total dust, carbon monoxide, carbon dioxide, sulphur dioxide, hydrogen fluoride, benzene, and phenol were above the recommended standards in 56.9 % (74/130) of the samples. After modernisation, only 12.3 % (21/171) of the samples were non-conforming. Before modernisation, workers were exposed to higher concentrations of all agents in all production sections. After modernisation, dust remained the primary pollutant in harmful concentrations in the anode baking furnace (GM=22.1 mg m-3) and in the anode rodding room (GM=22.1 mg m-3), hydrogen fluoride in the anode rodding room (GM=4.2 mg m-3), and sulphur dioxide in all production sections. As plant modernisation has not completely resolved the exposure issue, stringent compliance to safety rules and regular medical checkups are necessary.