Pre-industrial and recent data series were used to assess the evolution of ozone concentrations in northern Portugal, being the results analysed according to the atmospheric chemistry. Compared to the nineteenth century, current concentrations were in average 147% higher due to the increased photochemical production, associated with the increased anthropogenic emissions. The models developed were considered valuable tools for public health protection because they could make efficient predictions of ozone levels, thus allowing to provide early warnings to the population. The impact of ozone...