US President Donald Trump has announced the reversal of the so-called endangerment finding, a key Obama-era scientific ruling that underpins much of US environmental legislation.
As a result of this, experts are predicting various environmental and economic impacts, though the decision by the US Environmental Protection Agency (EPA) is expected to be challenged in the courts from environmental groups.
Here are some of the potential impacts:
Fewer greenhouse gas emissions restrictions
The most obvious outcome of the legislative change is that there will be fewer restrictions placed on greenhouse-gas-producing industries - in particular vehicle manufacturers.
The 2009 endangerment finding was the result of a major report by the EPA, which identified six greenhouse gases, including carbon monoxide and methane, as endangering current and future generations.
The EPA produced the report after a 2007 US Supreme Court decision that it was responsible for regulating greenhouse gases under the Clean Air Act - with the court ruling that these gases counted as air pollutants. Greenhouse gases trap heat in the atmosphere, raising temperatures.
The impact of the ruling until now has been notable. Greenhouse gas levels in the US peaked in the late 2000s and have been on a steady decline in the years since. With the endangerment finding gone, so is much of the legal basis limiting US industries in the amount of greenhouse gases they are allowed to emit.
Non-profit group the Environmental Defense Fund estimates that there will be an additional 7.5-18 billion tonnes of greenhouse gases emitted by 2055, which could cost trillions of dollars.
Cheaper cars in the US (but they'll be harder to export)
While there has already been a backlash from environmental groups, the Trump administration says removing the endangerment finding will be economically beneficial, particularly when it comes to the cost of vehicles.
Reversing the finding will reduce automobile manufacturers' costs by around $2,400 per car, the White House claimed. However, producers are likely to face challenges in other markets due to evolving climate targets worldwide.
Nuisance lawsuits
The endangerment finding meant that the EPA had the power for regulating greenhouse gas emissions. With the finding gone, legal experts predict an increase in public nuisance lawsuits against companies that pollute.
Public health
The EPA's announcement stated that maintaining emissions standards was not essential for its mission to protect human health. However, studies indicate that higher emissions correlate with health problems, potentially leading to significant premature deaths and increased health-related incidents.
Falling behind in the global renewables race
Removing restrictions may help domestic industries in the short term, but critics worry this could hinder the US's progress in renewable energy innovation compared to other countries, particularly China and the EU.
Less industry regulation
While the administration argues reduced regulation could lead to an economic boost, experts highlight the potential long-term consequences of abandoning environmental standards on global competitiveness.
