The Trump administration has quietly deleted or reshaped nearly 400 federal datasets over the past year and a half, a shift that researchers say could leave the country without the information it needs to protect public health and safety. At least 28 federal datasets have disappeared entirely, while another 338 have been altered in some way, according to a new online tracker launched last week by dataindex.us, a group of data policy experts, researchers and developers formed last year specifically to watch for changes to government data.

The datasets affected stretch across more than 60 federal agencies and touch on everything from the environment and labor to law enforcement, as per a report from The Guardian. Among the casualties are a database tracking misconduct by federal law enforcement officers, a survey measuring violence against children and youth, and real-time pollution data gathered by air quality monitors at US embassies worldwide.

Denice Ross, who served as the country’s chief data scientist under the Biden administration and co-founded dataindex.us, said the loss of this information puts the nation in a precarious spot. She warned that without solid data, decision-makers will struggle to make choices that protect lives and support communities across the country.

The Centers for Disease Control and Prevention has stripped gender identity questions from several major surveys, including its National HIV Surveillance System, which serves as the primary data source for HIV case tracking nationwide. Other affected CDC tools include the National Violent Death Reporting System, the Diabetes Prevention Recognition Program, the National Intimate Partner and Sexual Violence Survey, and surveys that track PrEP usage among gay men and communities of color.

At least four health datasets have stopped being updated altogether. One of them is the Drug Abuse Warning Network, run by the Substance Abuse and Mental Health Services Administration, which doctors and researchers relied on to monitor drug-related emergency room visits in close to real time and catch emerging overdose trends before they spiralled.

Complicating things further, many federal datasets are updated on a regular schedule, which makes it tricky to tell the difference between a routine refresh and a permanent deletion. Dick said the central question driving the project is whether datasets that matter to everyday Americans are being taken away.

To build the list, the group combined research into how each dataset had been used, tips crowdsourced from journalists, government employees and people who relied on the data directly, monitoring of social media, and tracking of notices tied to proposed regulations from the Office of Information and Regulatory Affairs.

Ross was clear that the tracker doesn’t capture everything and is likely still undercounting the true scale of what has been lost. Still, she said the goal is for it to serve as a starting point for understanding the damage.