Arsenic and other heavy metals in hydropower plants : An assessment of occupational risk hazards at Fortum’s underground hydropower plants in Sweden

Sammanfattning: Arsenic (As) is a metalloid that occurs naturally in the Earth’s crust, in bedrock and soil. The concentrations that Arsenic can be found are normally between 1-3 ppm. However, the concentrations vary naturally between different locations on the globe, and usually places that have sulphur-rich and shale deposits are linked to higher concentrations of Arsenic. Elemental Arsenic and especially inorganic Arsenic have been classified as human carcinogens, with long term exposure causing adverse effects like skin and lung cancer. The objective of this study is to investigate whether or not Fortum’s underground hydropower plants in Sweden, are within areas that present higher concentrations of Arsenic and if so, to assess if there may be any occupational risk hazards for the maintenance personnel while working in the plants. Based on SGU’s open geochemical database a map of Arsenic’s geospatial distribution was constructed, and according to that map and locations of Fortum’s underground stations, seven of them were selected to be further studied. Since the most relevant exposure pathways for the personnel in the plants, were considered to be intake of groundwater and inhalation of dust, samples of water and bedrock were collected from the selected plants, to be analyzed in the lab for the metal concentrations. Moreover, to better comprehend and assess the ways the personnel is exposed to the hazardous materials, a questionnaire was handed to them during the field visits. The results from the lab analyses of the rock samples, showed increased concentrations of Arsenic in the sample from Järpströmmen (9 ppm), and the samples from Anjan (4.5 ppm) and Kvarnfallet (4.6 ppm). However, all water samples concentrations in Arsenic were below the permissible limit of 10 μg/L. Although, the tap water sample from Anjan hydropower plant presented high content of Manganese and Iron associated to the bedrock deposits, and the tap water sample from Krångede presented high copper concentrations, associated to the existing piping system. According to these results, a few simple remediation actions were suggested for two abovementioned locations. It was concluded, by combination of all results from lab analyses of rock, water samples and questionnaire responses, that under current conditions, there are no unacceptable human health risks, due to exposure to arsenic, for the personnel working in the plants. However, it is advised that in the case that a new activity changes the steady state conditions, a new investigation should take place.