Atmospheric mercury pollution: the current methodological framework outlined by environmental legislation

Mercury is a toxic pollutant that exists in the atmosphere in several forms, operationally identified according to their chemical and physical characteristics. The problem of atmospheric mercury pollution has recently received increasing attention, as evidenced by the numerous European regulations issued in the last years. The normative question is closely related to the methodological one, as the quantification of the mercury species is strictly linked to the sampling and analysis methods. Due to their different bioavailability, airborne mercury forms detection is fundamental both in outdoor and indoor (i.e., workplace) environments. This paper presents an overview of European legislation on atmospheric mercury pollution, with particular attention to the Italian legislation. Starting from the regulatory protocols, the methodological framework for mercury quantification was reviewed, underlining the limits and the problems of the different methodologies and providing new guidance for the analysis. Regulatory and methodological updates have led to great specificity in mercury quantification, which is distinguished for the outdoor and indoor environments. For workplace environments, all mercury species (i.e., gaseous and particulate mercury) are required to be quantified by the Italian legislation; on the contrary, only gaseous compounds are monitored in outdoor conditions. It hence appears of primary importance that the monitoring operator chooses the sampling and analytical method for mercury sampling and analysis that correctly adheres to the normative regulations. Detailed norms describe how to carry on the monitoring in both outdoor and indoor conditions, preventing the operator's arbitrariness, which otherwise can lead to airborne mercury underestimation/overestimation.