* Ethical investors to increase pressure in event of no reply. : LONDON, June 17 (Reuters) - Investors with a combined $12.5 trillion in assets, including the Swedish National Pension Funds and the Church of England, could review their stakes in resource companies that use storage dams if they do not release information to assess safety risks. The safety of dams used to store mining waste, known as tailings, gained prominence after the collapse of Vale’s dam at Brumadinho in Brazil in January, which killed about 250 people.