The rise of the on-demand or “gig” economy creates new safety challenges for workers in the growing employment sector and raises questions about how to ensure they are covered if they are injured while working.

For instance, the Washington state Department of Labor & Industries in October ordered San Francisco-based delivery service Postmates Inc. to retroactively pay workers compensation premiums for over 3,000 of its couriers in the state, according to documents provided by the department.

Postmates, which allows customers to order groceries and other items through an app, considered its couriers to be independent contractors and did not cover them under workers comp. But the Washington state labor department — the state’s monopoly workers comp insurer — found that Postmates should have paid $323,027 in audited workers comp premiums for those workers. The company was also charged $75,275 in penalties for insufficient record keeping, according to documents provided by the department.

Robert Rieders, general counsel for Postmates, said the company has contested the decision.

Postmates is one of the many companies that rely on what is known as the on-demand economy. Those include San Francisco-based ride-sharing firms Uber Technologies Inc. and Lyft Inc. and TaskRabbit Inc., a San Francisco-based company that allows app users to contract people to perform tasks such as handiwork or cleaning.

There are several definitions for the on-demand economy, but the broadest is “any source of income where the workers and the clients are connected by a digital platform,” said Kristin Sharp, Washington-based executive director of the Shift Commission on Work, Workers, and Technology, an initiative of non-partisan public policy think tank New America and financial media company Bloomberg L.P.

With the rise of workers taking on on-demand jobs, its relationship to workers comp has become a focal point, observers say. While technology may make things easier for consumers, on-demand economy workers do not avoid worker safety risks.

“A lot of the on-demand jobs are among the most dangerous in the country. In particular, for-hire transportation is a very hazardous industry,” said Deborah Berkowitz, Washington, D.C-based senior fellow, worker safety & health at the National Employment Law Project.

Drivers for services like Uber and Lyft face the same risks as taxi drivers and chauffeurs who are killed on the job at a rate five times higher than the average for other workers, Ms. Berkowitz said. In addition, companies such as Postmates use bicycle delivery, which also leads to occupational hazards, she said.

While some experts believe that the current workers compensation framework can accommodate on-demand economy workers, others say comp insurers have been slow to respond to this new category of workers and states may have to step in with alternative coverage arrangements for injured on-demand workers.

“A business can hire gig workers to do their job and that business is free to classify those workers as employees for work comp purposes and purchase a work comp policy and they would be covered,” said Steven A. Bennett, Washington-based associate general counsel and director of workers compensation programs at the American Insurance Association. “Our view is that no major changes have to be done to the work comp system to adapt to the gig economy.”

But workers comp insurers have yet to respond to the on-demand economy, said Los Angeles-based Edward Canavan, vice president of the workers compensation practice and compliance at third-party administrator Sedgwick Claims Management Services Inc.

After learning more about the evolving on-demand industry, workers comp insurers may begin to address the on-demand economy down the line, Mr. Canavan said.

“If I was a carrier, I would start thinking about coverage issues, I would start thinking about liability issues, I would start thinking about cost shifting ... could these workers potentially be tempted to shift costs somewhere else because they don’t have coverage,” he said.

Postmates and other companies that rely on gig economy workers could have to make changes to their business structure if they are required to provide workers comp coverage to workers that are currently considered independent contractors, experts say.

“Much of the on-demand economy is not structured around having a business model where they employ full-time workers,” said Ms. Sharp of the Sharp Commission.

“If judges increasingly rule that online platforms are employers, that changes the economic calculus of those companies, and I think you will see some go out of business and some that adapt and hire full-time workers,” she added.