In 2009, two studies commissioned by the UK-based advocacy group CAFOD have found the company's methods to extract gold from low-grade deposits also releases other toxic heavy metals such as arsenic, mercury and lead, contaminating streams and groundwater. The first study from Newcastle University detected acidic mine drainage, whereby sulphides in the rock are exposed to oxygen and water and produce sulphuric acid, which can have devastating effects on animals and plants. A follow-up study by the same university found evidence of "severe" contamination in the form of highly acidic and metal-rich water from the mine site flowing into a stream used by villagers for agriculture and domestic purposes.