Bitcoin dropped 10% after Elon Musk tweeted: 'We are concerned about rapidly increasing use of fossil fuels for bitcoin mining and transactions, especially coal.' On an annual level, the mining of bitcoin uses as much energy as the Netherlands did in 2019. Two-thirds of bitcoin is mined in China by using data centers reliant on electricity generated by coal. Environmental risks are a new concern which will impact bitcoin and other cryptocurrencies. There is also growing pressure to regulate cryptocurrencies as was noted in the report of the Bank for International Settlements (BIS). Regulatory concerns are the main danger, and will substantially affect the growth of cryptocurrencies.