Elizabeth Warren and other Democratic members of Congress issued a letter to two federal regulators on Friday, pushing them to take action in response to the surge in Bitcoin mining in the United States.

The letter, which was sent to the chiefs of the Environmental Protection Agency and the Department of Electricity, was prompted by a preliminary assessment conducted by MPs, which discovered that only a small number of crypto miners consume a significant amount of energy.

In response, lawmakers have asked the agencies to require crypto-mining companies to publish data on their energy consumption and emissions.

With over 300 million users worldwide, the #cryptocurrency field has been booming during the last few years, so how does the future look like for crypto?#Bitcoin #OmicronVariant pic.twitter.com/C6PHTcl8RC

— Al Mayadeen English (@MayadeenEnglish) December 15, 2021

What does the letter say?

According to the letter, seven of the largest crypto-mining companies in the United States have a combined capacity of more than one gigatonne of electricity. That's the equivalent of two typical coal plants, or, as the letter puts it, nearly enough to power all of Houston's houses.

That's just the tip of the iceberg because there are no regulatory standards in place to capture a comprehensive picture of the environmental impact of the recent surge in crypto-mining in the US.

Read next: Crypto miners turn to solar power in Texas

Crypto-mining has grown in the US over the last year, fueled in part by China's crackdown on the practice in 2021. The US is the world's largest mining hub, with data centers operating around the clock to mine the money.

These data centers are crammed with specialized technology racing to solve difficult equations to verify transactions and earn Bitcoin. All of that computational capacity consumes enormous amounts of electricity, resulting in pollution.

Moving from China to the US has almost certainly made the Bitcoin network dirtier, as ample hydropower in China has been replaced with coal and gas-derived electricity from the US grid.

Crypto and Climate Change 

All of this has politicians concerned about the impact of cryptocurrency mining on the country's climate change goals as well as electricity bills. In New York, for example, the practice has already raised electricity rates. Residents in Plattsburgh, New York, for example, saw their utility costs climb by up to $300 in the winter of 2018 when Bitcoin miners set up shop nearby.

Two-year freeze in NYC

New York State approved legislation last month that imposed a two-year freeze on new permits for fossil fuel power plants used to mine energy-intensive currencies. Although the bill has not yet been signed into law, the state has taken regulatory steps to discourage mining.

Read next: Change in coding could reduce bitcoin energy consumption

In June, New York refused a renewal of an air permit to a troubled power plant, the Greenidge Generating Station, claiming that its usage for Bitcoin mining would be "inconsistent with the statewide greenhouse gas emission limits."

Greenidge

Greenidge was one of the corporations to which Warren and other Democratic lawmakers issued requests for information on their energy use and emissions in January.

According to the new letter, Greenidge was responsible for 273,326 tons of carbon dioxide emissions over a year, which is equivalent to the exhaust emissions from over 60,000 cars.

Nonetheless, the impact of cryptocurrency mining in the United States is far more than what the letter describes. To begin, the MPs stated that "none of the companies provided full and complete information in response to our questions."

Read next: The White House Considers Measures to Monitor Cryptocurrency Use