President Donald Trump speaks during a rally at the St. Charles Convention Center on November 29, 2017 in St. Charles, Missouri.

President Donald Trump donated his third-quarter salary to the Department of Health and Human Services, to help the agency combat the opioid epidemic, the White House and HHS announced Thursday.

"His decision to donate his salary is a tribute to this compassion, to his patriotism and his sense of duty to the American people," said HHS acting secretary Eric Hargan, who attended the White House daily press briefing.

The opioid epidemic, Hargan said, is killing 175 Americans every day, and "we're losing seven fellow Americans during this press briefing alone."

Trump declared the opioid epidemic a national public health emergency in October, a move that freed states to allocate more federal health-care dollars to fighting and treating the epidemic.

Hargan also noted that both he and the president have been personally affected by addiction: Trump's older brother Fred Trump suffered from alcoholism for much of his life; Hargan told reporters he has a family member who was addicted to opioids.

Like both Barack Obama and George W. Bush before him, Trump makes an annual salary of $400,000, meaning that his donation to HHS was around $100,000.

During his 2016 presidential campaign, Trump pledged to donate his entire presidential salary to charity.