Every one of us endures stress of some kind in our workplace, and at varying times. A quality defining many of the CareerCast.com most stressful jobs of 2016 is that stress is virtually omnipresent, and the spikes in periods of high stress are unpredictable.

Stress, as defined by the Jobs Rated methodology, is determined by 11 factors: travel, deadlines, working in the public eye, competitiveness, physical demands, environmental conditions, hazards encountered, the life of oneself or others at risk, meeting and interacting with customers and/or the public, and the potential for job growth.

Thus, jobs can be remarkably stressful, albeit for remarkably different reasons. The stress inherent with working as a police officer or firefighter, for example, is readily apparent.

Firefighters and police officers face life-threatening situations routinely as a fundamental part of their jobs.

The Officer Down Memorial Page tracks on-the-job fatalities in the American police force with the goal of honoring those lost in the line of duty. ODMP reports 119 officer deaths in 2015, as of Dec. 18.

The U.S. Fire Administration reports 80 fatalities in the line of duty in 2015. Personal danger is just one of the stress factors faced in these careers. Police officers and firefighters, as well as enlisted military personnel, are entrusted with the safety and well-being of others – another key element weighed in the Jobs Rated report.

The kind of stress some of the other careers ranked among the Jobs Rated report’s most stressful of 2016 differs vastly. For example, a public relations agent’s stress comes from tight deadlines, oftentimes out of the agent’s control, and meeting in the public under sometimes inhospitable circumstances.

“Since news happens 24/7, I've been woken in the middle of the night [and] had to get a pitch out on weekends, holidays,” says Fort Lauderdale, Florida-based PR agent Bruce Serbin.

And sometimes, the message presented is met with hostility. “Sometimes, you are berated for disturbing the reporter or offering them a story they aren’t interested in,” says Lauren Littlefield, president of Field Public Relations in Indianapolis. “It takes a thick skin to put the phone down and try again.”

Client demands can contribute to workplace stress no matter the field, and both public relations agents and event coordinators face some considerable demands from their clientele.

In less-than-ideal scenarios, PR agents are the public face when a client needs damage control. However, even in less dire straits, balancing client demands with public response is a source of stress.

“A big challenge in PR — and this doesn't happen in every case — is getting a client to understand the story from the audience's point of view,” Philadelphia-based PR agent Alexandra Golaszewska told CareerCast.com in an email. “Sometimes, people are so close to their businesses that they have a hard time seeing what's compelling, or not so compelling, to those who aren't connected to the company.”

Reconciling a client’s vision with a successful end-result is one of the stressful elements of working in event coordination. Bringing together ideas and turning them into a functioning, large-scale event takes an unflappable professional.

“Event planners deal in emotion, so you have to be the calming force in the room,” says San Diego-based event coordinator Nicole Matthews.

Some people have the personality to handle stress gracefully. Likewise, some are cut out for working in the public eye almost exclusively, though most aren’t. Hence the prevalence of glossophobia, or fear of public speaking, which afflicts an estimated 75% of Americans.

For three-quarters of the population, a broadcaster’s line of work would be terrifying. But, just like the other jobs ranked our most stressful of 2016, to those in the field, it’s rewarding.

“PR is a highly satisfying career,” Littlefield says. “No day is like another. It’s fast paced, exciting and very rewarding to those who do it well.”

The following are the 10 most stressful jobs of 2016, according to the Jobs Rated report. Growth outlook and salary information is per U.S. Bureau of Labor Statistics estimates, released Dec. 2015. Outlook projections span from 2014 to 2024.