Disengaging and divesting from thermal coal, oil sands and oil shale Fossil fuels emit carbon dioxide (CO2) when burned and extracting them can harm the environment. We are working with customers and companies in which we invest that have more than 30 percent exposure to thermal coal, oil sands and oil shales to help them to reduce their use and exposure to these fuels. Zurich will also generally no longer underwrite or invest in companies generating more than 30 percent of their revenue from mining or more than 30 percent of their electricity from thermal coal.