The extreme cold that killed at least 21 people in the Midwest—including a 69-year-old FedEx Corp. employee found dead Jan. 31 in a company parking lot—highlights the risk to employees forced to work outside.

The Occupational Safety and Health Administration is investigating the death of a 69-year-old William Murphy, whose body was found between two semi tractors at a FedEx Freight delivery hub in East Moline, Ill., Scott Allen, a spokesman for the agency’s regional office in Chicago, told Bloomberg Law. Temperatures reached as low as 33 degrees below zero in the city this week, according to the National Weather Service, putting workers at risk of illnesses and injuries like hypothermia, frostbite, and trench foot. OSHA under federal law has six months to issue any citations to FedEx.

Symptoms of hypothermia include shivering, fatigue, loss of coordination, and confusion, according to guidance from the National Institute for Occupational Safety and Health, a federal research agency. If not treated, workers will see worsening conditions, including blue skin, dilated pupils, and slowed pulse and breathing and they’ll eventually lose consciousness.

Temperatures are expected to ease this weekend, reducing the risk for now. The underlying weather phenomenon, though, will keep appearing. Scientists say warmer Arctic air is making the jet stream weaker, pushing frigid air to the Midwest more often.

That could bring more risks for outdoor workers in airports, distribution centers, and logistics hubs like FedEx, United Parcel Service Inc., the U.S. Postal Service, Walmart Inc., and Amazon.com Inc., as well as airlines such as United Airlines Inc., Southwest Airlines Co., American Airlines Group Inc., and Delta Air Lines Inc.. Not only can the cold cause frostbite or hypothermia, it can exasperate existing health problems like dehydration and increase the risk of a heart attack.

OSHA policy states deaths are considered work-related if they result from exposures in an area where an employee is working or is present as a condition of employment. Workplace deaths by natural causes such as heart attacks are reportable, and the agency decides to investigate based on the circumstances of the death, policy directives state.

“We are saddened by the loss of our team member and our sympathies go out to his family and friends,” Jim McCluskey, a spokesman for FedEx in Memphis, Tenn., said in a statement to Bloomberg Law. “We are working with local authorities as they investigate.”

Training, Equipment

Companies that operate outdoors can face OSHA citations if they fail to protect workers, Travis Vance, labor and employment partner at the law firm Fisher Phillips in Charlotte, N.C., told Bloomberg Law in an email. While no specific standard addresses the cold, OSHA can cite employers under the general duty clause. Penalties by law are limited to $13,260 per violation but can be as much as $132,598 for each willful or repeated violation if an employer knew about the risk but failed to take action, or has been previously cited for a similar offense.

Starting points for precautions for outdoor workers in the polar vortex should include providing gloves, hats, and clothing sufficient for the temperatures expected, Vance said, and training staff to look for physical signs of overexposure to the cold. Employers also should consider outdoor heaters and rotating workers inside to warm up, Vance said. If it’s too cold for those methods, employers should pull workers off the job until conditions improve.

Delta rotated airport employees indoors during the cold, which affected major hubs in Minneapolis and Detroit, said Michael Thomas, a spokesman for the airline in Atlanta. The company introduced uniforms for staff produced by outdoor retailer Lands’ End that are rated for low temperatures, Thomas said. Staff also had the option of taking shelter inside heated employee shuttle buses left idling on the tarmac.

UPS covers winter safety in its Comprehensive Health and Safety Process program, an employee-led wellness program launched in 1995, as well as with ongoing training, Dan McMackin, a spokesman for the company, told Bloomberg Law.

Mail delivery was suspended in parts of the Midwest amid the low temperatures, David Partenheimer, a spokesman for the United States Postal Service in Washington, said in an email to Bloomberg Law.

Staff know that “if weather conditions are unsafe, they should curtail delivery and report back to the office or more to a warm, dry place immediately,” Partenheimer said.