Sunday is International Overdose Awareness Day, and those who frequent the Boston Common have already witnessed the memorial to lives lost in the commonwealth.

Volunteers were supported by the Boston Public Health Commission and the city Parks and Recreation Department in planting more than 20,000 purple flags in the park to memorialize those who have died in the opioid epidemic.

“Opioid overdose deaths are tragic, and avoidable,” said Dr. Bisola Ojikutu, the city’s public health commissioner. “I’m proud of the progress we’ve made in reducing fatal overdoses in our city, and the best way we can honor the lives tragically cut short by the opioid crisis is by continuing to increase access to harm reduction services and treatment for those living with substance use disorder.”

In addition to the purple flags, Boston will also light up City Hall in purple Sunday night.

“Today we are honoring the lives lost to fatal overdoses that have touched every corner of Boston’s communities,” said Mayor Michelle Wu.

The city will also host events through September, which is National Recovery Month.

More information can be found at the BPHC website at Boston.gov/government/cabinets/boston-public-health-commission/.