Jared Huffman, a member of the United States House of Representatives, and twelve other legislators have asked that the Environmental Protection Agency (EPA) assess any crypto mining companies potentially violating environmental laws.

Huffman addressed a Wednesday letter to Michael Regan (EPA administrator) he and other Democratic House members had “serious concerns” around crypto firms in the United States reportedly contributing to greenhouse gas emissions and not operating in accordance with either the Clean Air Act or the Clean Water Act. The lawmakers identified efforts to “re-open closed gas and coal facilities” as a means to produce energy for crypto mining operations as a particular area of concern, as well as “energy-inefficient” proof-of-work mining for (BTCEther (ETH), Monero (XMR), and Zcash (ZEC).