Georgetown University researchers have released yet another report warning of the potential dangers and ineffectiveness of the beginnings of routine facial recognition scanning by certain airlines at a handful of airports nationwide.

The new report, which was released Thursday, comes on the heels of a related 2016 report showing that half of Americans’ faces are already in a facial recognition database.

“As currently envisioned, the program represents a serious escalation of biometric scanning of Americans, and there are no codified rules that constrain it,” the report concludes.

In July 2017, Ars reported that facial-scanning pilot programs are already underway in international departure airports at six American airports—Boston, Chicago, Houston, Atlanta, New York City, and Washington, DC. More are set to expand next year. In a recent privacy assessment issued one month earlier, DHS noted that the “only way for an individual to ensure he or she is not subject to collection of biometric information when traveling internationally is to refrain from traveling.”

Laura Moy , a Georgetown law professor and one of the report’s authors, spoke with reporters on the phone. She said that, between the time the research was completed and its publication, she and her fellow researchers had found out that Los Angeles International Airport is now also on this list.

“We’re wondering if this is the best use of a billion dollars?” she said. “We’ve done the research and we think the answer to that question is ‘no.’”

Sen. Ed Markey (D-Mass.), who spoke for a few minutes, applauded the research.

“When American citizens travel by air, they should not have to choose between privacy and security,” he said. “The implementation of DHS facial scanning program for US citizens leaving the country raises a number of questions.”

He urged DHS and airlines that participate in the expanding program to clearly inform “every American citizen that they have the right to opt out of facial scanning.”

The senator also pointed out that DHS has said it has a goal of a “96 percent” accuracy rate, which he said was inadequate.

“That means that four percent of travelers will be improperly flagged by the scanning program,” Sen. Markey said. “This could still result in a false denial for one out of 25 travelers.”

In response to Ars’ question, Markey admitted that he did not know if he himself had already been scanned at Logan International Airport in Boston or Dulles International Airport near Washington, DC.

“The pilot program is limited, so I probably have not. But I don’t know that with 100-percent certainty.”