President Donald Trump issued a proclamation on Oct. 24 aimed at reversing a Biden-era environmental rule that enforced stricter air emission standards on copper smelters.

The proclamation grants local copper smelters a two-year exemption from compliance with the 2024 rule that had required them to cut emissions of hazardous air pollutants such as lead, arsenic, and mercury.

In a fact sheet, Trump described the Biden-era emission standards on copper smelters as “overly restrictive” and said that they could undermine U.S. mineral and metal supply chains.

The president said that the regulatory relief would help cut U.S. reliance on foreign supply chains and secure the nation’s mineral security.

“Imposing these requirements on such a limited and already strained domestic industry risks accelerating further closures, weakening the Nation’s industrial base, undermining mineral independence, and increasing reliance on foreign-controlled processing capacity,” Trump stated in the proclamation.

The United States currently has two primary copper smelters, operated by Freeport-McMoRan and Rio Tinto. Neither company has issued any statements regarding Trump’s proclamation.

Copper is an essential component for the electric grid and semiconductor production. The proclamation states that copper plays a critical role in strengthening the nation’s energy, defense, and manufacturing sectors.

In July, Trump announced on Truth Social a 50 percent tariff on copper imports following an investigation into whether those imports pose a risk to national security. The tariff took effect in August.

Trump noted that copper is needed for manufacturing semiconductors, aircraft, ships, ammunition, data centers, lithium-ion batteries, radar systems, missile defense systems, and hypersonic weapons and is the second most used material by the Department of Defense.

“I am announcing a 50 [percent] tariff on Copper, effective August 1, 2025, after receiving a robust national security assessment,” he stated. “America will, once again, build a dominant Copper Industry.”

The tariff followed an executive order Trump signed on Feb. 25, in which he directed Commerce Secretary Howard Lutnick to initiate a Section 232 national security probe into copper imports.

China now controls more than 50 percent of global copper smelting capacity and holds four of the top five biggest refining facilities, the order said.

The United States’ dependence on copper imports has risen from nearly zero in 1991 to 45 percent of total consumption in 2024, increasing supply chain security risks, according to a White House fact sheet.

“This dominance, coupled with global overcapacity and a single producer’s control of world supply chains, poses a direct threat to United States national security and economic stability,” Trump stated.

The United States produced about 1.1 million tons of copper in 2024, which was valued at an estimated $10 billion, according to the U.S. Geological Survey. Arizona accounted for 70 percent of the nation’s copper output.

Other copper-producing states include Michigan, Missouri, Nevada, New Mexico, and Utah, according to the report.

Joseph Lord and Tom Ozimek contributed to this report.