Thanks to the government shutdown, nearly a dozen federal Web sites are offline and 19 of them are no longer being updated. But a less obvious casualty of the widespread furloughs are the online tools that automatically relay government data to the public.

Federal agencies maintain hundreds of application programming interfaces, or APIs. Whenever you see an interactive map that's based on Census statistics or pollution data or other official information, that's often the result of a government data feed. These days, however, when a map or a program phones in to the feed for updates, it's often met with a "sorry, we're closed" message — just like the kind human visitors see when they visit

Craig Isakow runs the D.C. office of a Boston-based company called WegoWise, which helps offices, schools and other public buildings become Energy Star-recognized with the Environmental Protection Agency. Using the agency's API, Isakow submits characteristics about a building's size and energy usage, and the API returns a numerical score from 1-100 that can be read like a fuel-efficiency rating for cars. Last year, Isakow said, nearly a third of all such Energy Star scores were generated using the API; the rest were computed by logging in by hand.

Now both methods of performance certification are down as a result of federal furloughs. That means delays, lost revenue and greater uncertainty for WegoWise.

"If [the shutdown] is prolonged, it's definitely going to slow our sales to commercial buildings," said Isakow. "Taking down these systems the private sector depends on affects people's pocketbooks immediately."

Losing access to the Energy Star API also has consequences for state and local governments that have made Energy Star scores a requirement for commercial buildings within their jurisdiction. That includes Austin, San Francisco, Seattle and Washington, D.C., which have all instituted some kind of mandatory commercial Energy Star reporting. In the nation's capital, the reporting deadline was Oct. 1; that date has now been pushed back to seven days after the resumption of federal operations.

Meanwhile, APIs for important health monitoring applications are also down. The Centers for Disease Control maintains an API for its national cancer registry, which tracks various cancer-patient statistics. Data about new cancer cases may still be being compiled by cities and states, but it's not making its way into the national database because the servers are unresponsive, said Maksim Tsvetovat, founder of the D.C.-based Open Cancer Network.

Tracking cancer-causing agents has become more difficult, too. Tsvetovat relies on another EPA tool called the Enforcement and Compliance History Online, or ECHO. ECHO keeps a record of every industry compliance violation reported by the EPA. With the ECHO API, said Tsvetovat, "if a power plant or oil refinery has a benzene release, we can issue an alert geographically to people who are sensitive to this kind of stuff."

Benzene is a known carcinogen, so getting that information to at-risk populations is key. But with the closure of the API, the database isn't being updated. If the shutdown lasts for longer than a week or so, the feed will no longer be useful.

The good news is that the historical data companies have already downloaded from government servers won't be affected by the shutdown. So for people who are interested in using past data for research will still be able to do their work. But for the businesses and individuals who rely on timely federal data for their livelihoods, having the tap turned off is far worse than encountering a dead Web site.