Bioaccumulation and biological effects of hydrogenated cement particles in the marine bivalve, Mytilus galloprovincialis

The decommissioning and normal functioning of nuclear facilities can result in the production and release of airborne particles in the environment. Aquatic biota are expected to be exposed to these particles considering that nuclear facilities are often located near water bodies. Aerosols, including tritiated (radioactive) and non-radioactive particles such as cement dust, can interact with radionuclides as well as with heavy metals, and therefore elicit not only radiological but also chemical toxicity. In the present study, we aimed to determine the effects of hydrogenated cement particles (HCPs) as a first step before evaluating any radiotoxicity of tritiated cement particles in the marine mussels, Mytilus galloprovincialis. Responses at different levels of biological organisation were assessed, including clearance rate (CR), tissue specific accumulation, DNA damage and transcriptional expression of key stress related genes. Acute (5 h) and medium-term, chronic (11 d) exposures to 1000 μg L-1 HCPs showed that bioaccumulation, assessed using Cu as a proxy and determined by inductively coupled plasma mass spectrometry, was time and tissue dependent. The highest levels of Cu were found to be in the digestive gland (DG) after 11 d. HCP exposure caused changes in the expression of oxidative and other stress-related genes, including mt20 in DG, gst and sod, in the gill after 5 h exposure, while an overexpression of hsp70 in the gill was observed after 11 d. Genotoxic effects in haemocytes were observed after 11 d of HCP exposure. Multivariate analysis indicated that oxidative stress is the most probable factor contributing to overall physiological (i.e., CR) dysfunction. Our results provide a baseline to perform further studies employing tritiated cement particles. Specifically, future work should focus on the DG since only this tissue showed significant bioaccumulation when compared to the negative control.