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.
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.
Greenhouse gases trap heat in the atmosphere, raising temperatures. The impact of the ruling until now has been notable, with greenhouse gas levels in the US peaking in the late 2000s and having been on a steady decline since then. 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, potentially running into trillions of dollars in costs.
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 claims that removing the endangerment finding will reduce automobile manufacturers' costs by around $2,400 per car.
Ford and the Alliance for Automotive Innovation have welcomed the change, but it also raises concerns about the competitiveness of American cars in international markets with stricter emission standards.
Nuisance lawsuits
The absence of the endangerment finding may lead to a resurgence of lawsuits for public nuisance related to pollution, as it gives states more power to regulate emissions again.
Public health
The EPA stated that existing greenhouse gas emissions standards were not critical for protecting human health and the environment. However, scientists warn that these pollutants can cause health problems and may lead to thousands of premature deaths and asthma attacks by 2055.
Falling behind in the global renewables race
As the US retracts from clean vehicle standards, industry experts fear that American automakers may lag behind other nations that are advancing in renewable energy technology.
Less industry regulation
The Trump administration argues that deregulatory measures are essential for economic growth, predicting they will save American taxpayers over $1.3 trillion. Critics, however, warn that this could lead to dirtier manufacturing practices being outsourced to countries like China.
