Months after rubbishing any ideas of using a controversial type of armour-piercing round that has been linked with long term health related complications, the Pentagon has acknowledged that it used depleted uranium rounds during two high-profile air raids back in November 2015, The Washington Post reported.

The use of the ammunition came to light earlier this week when a report was issued by a joint Air Wars-Foreign Policy investigation, which stated that a 30mm depleted uranium bullet called PGU-14 had been fired during two air raids.

Approximately 5,200 rounds were fired from A-10 ground attack aircraft on November 16, 2015 and November 22, 2015, in airstrikes in Syria’s eastern desert. The strikes targeted the militant Islamic State (IS) group’s oil supply during Operation Tidal Wave II, confirmed US Central Command spokesman Major Josh Jacques.

The strikes involved the use of 30mm cannon fire, rockets and guided bombs, and helped destroy more than 300 vehicles, most of which were civilian tanker trucks, according to the Pentagon.

The two raids were championed by the Pentagon and footage of trucks being destroyed was posted online. The Pentagon also stated that no civilians were present during the attacks as fliers had been dropped before strafing runs warning those in their trucks to flee.

Earlier in February 2015, Captain John Moore, a spokesman for the US-led anti-ISIS coalition in Iraq and Syria, said in an email, "US and Coalition aircraft have not been and will not be using depleted uranium munitions in Iraq or Syria during Operation Inherent Resolve."

Later that year the Pentagon’s stance toward depleted uranium changed as US-led forces ramped up their campaign to go after the Islamic State’s cash flow, using depleted uranium ammunition in Operation Tidal Wave II to attack the militant outfit’s oil trucks in Syria and ensuring that the vehicles were rendered completely inoperable.

Depleted uranium rounds are used as armour-piercing rounds owing to the material’s high density, helping it penetrate certain tank shells.

Exposure to depleted uranium causes long term side effects, with the United Nations (UN) issuing a report in 2014 stating that direct contact with large amounts of depleted-uranium through the handling of scrap metal, for instance, could “result in exposure of radiological significance.”

However, there is no international treaty or rule that explicitly bans their use.

Major Josh Jacques did not rule out the possibility that the US-led coalition might use depleted uranium rounds again, adding that the locations where they were used in November 2015 have been marked for cleanup in the future.

However, as the area is still primarily controlled by the Islamic State, whatever scrap was left behind from the strikes has likely been recovered and sold.