Sampling of Total Mercury in Sand on Sydney Beaches and Assessment of Risk of Exposure to Children

Abstract:

Industrial waste, sewage outfall and storm water run-off are potential anthropogenic sources of mercury to Sydney beaches. Children playing on these beaches are possibly at risk of exposure to mercury in beach sand through the ingestion pathway. As part of an investigation into this risk samples were collected from various locations along 7 of Sydney’s beaches where children typically would be exposed. Samples were dried and the sand fraction (i.e. >63 µm and <2 mm) analysed for total mercury using a Direct Mercury Analyser (DMA-80) methodology. Risk of Exposure to mercury was assessed based on published estimates of daily ingestion of soil by children and Health Canada’s guideline of 105 ng Hg kg^-1 BW d^-1 exposure threshold. For the beaches sampled concentrations of total mercury in beach sand ranged from 0.6 to 58 ppb. The maximum concentrations of total mercury in beach sand were observed on Beach 6, in the vicinity of five storm water runoff sources. Daily mercury intake values were determined for two commonly used published values for daily ingestion of soil by children of 0.2 g soil d^-1 and 1.75 g soil d^-1. Results to date show the maximum daily intake calculated using an average child weight of 13 kg to be 7.8 ng Hg kg^-1 BW d^-1, well below the currently accepted daily intake threshold of 105 ng Hg kg^-1 BW d^-1.