The Trump administration is rolling back the US government’s strongest attempt to combat the climate crisis, weakening rules which compel auto companies to produce more fuel-efficient vehicles. Critics say the move will lead to more life-threatening air pollution and force Americans to spend more on gasoline.

The changes to Obama-era regulations will allow vehicles to emit about a billion more tons of heat-trapping carbon dioxide – equivalent to roughly a fifth of annual US emissions.

The rollback is one of dozens Trump officials have ushered to completion, seeking to bolster the fossil fuel industry amid intense opposition from Democratic-led states and pushback from world leaders.

Experts say the world is far off track in dealing with the climate emergency, following a year of record-breaking heat, rising hunger, displacement and loss of life due to extreme temperatures and weather disasters.

Donald Trump is expected to laud the new rule as a boost to the US economy, which has been hit by the coronavirus pandemic. His administration says weakening the standards will make cars about $1,000 cheaper, leading Americans to buy new and safer models more frequently and resulting in fewer crash fatalities.

The Environmental Protection Agency (EPA) chief, Andrew Wheeler, said in a statement: “Now, more than ever, this country needs a sensible national program that strikes the right regulatory balance for the environment, the auto industry, the economy, safety, and American families.

“[This rule] does all of those things by improving fuel economy, continuing to reduce air pollution, and making new vehicles more affordable for all Americans.”

Researchers dispute such logic.

Miles Keogh, executive director of the National Association of Clean Air Agencies, an organization of state and local air regulators, called the timing of the rule change “appalling”.

He said: “We know coronavirus preys on people with respiratory problems, and this dirty air rule will make more Americans vulnerable.”

The Obama administration required auto companies to make vehicles 4.7% more efficient each year. The Trump administration initially wanted to freeze any progress on fuel efficiency past 2020. But its final rule, written by the EPA and the Department of Transportation, sets an improvement rate of 1.5% per year – or an industry average of 40.4 miles per gallon by 2026.

That’s far less than the 2.4% per year by which the industry has said it will increase standards without any regulation.

The rollback has drawn opposition from nearly half of states and a significant portion of the auto industry. Twenty-three states and the District of Columbia, representing about half of US residents, sued over the changes. They said weakening the standards would kill about 2,000 more people and cause 50,000 more cases of respiratory illnesses, while making the climate crisis worse.

California has long instituted more stringent auto standards than the federal government, but the Trump administration has revoked the state’s authority to do so. The state last year struck a deal with four companies – Ford, Honda, Volkswagen and BMW of North America – to exceed what Trump is asking for and require cars, trucks and SUVs to get nearly 50 miles per gallon on average by 2026.

Democratic-run states and environmental advocates are expected to challenge the new regulation. They are already fighting the Trump administration over its weakening of dozens of other environment and public health protections.

Ann Carlson, a professor at the University of California in Los Angeles, said the legal fight will be “one of the hardest fought, in part because it’s the most significant”.

Carlson believes the rollback is meant to maintain demand for gasoline, which is expected to fall as vehicles become more efficient and transition to electricity.

“You can make cars with zero emissions now, zero greenhouse gases that don’t run on petroleum, any more,” Carlson said. “So I think the big beneficiaries are absolutely the oil companies.”

The rule change comes as many communities around the US are seeing a decline in air quality, a result of climate change, wildfires, higher temperatures, regulatory rollbacks and poor enforcement of regulations, said Paul Billings, senior vice-president of advocacy for the American Lung Association.

“This will mean there will be more pollution associated with oil extraction, transport, refining – sort of all the way from the well to the pump,” Billings said. “This will mean high levels of smog, more coughing, wheezing, shortness of breath, asthma attacks, COPD (chronic obstructive pulmonary disease) exacerbations and also more particulate pollution.”

The effects will be worse on communities near oil processing facilities and highways, often people of color and poorer Americans.