Is idling in your car bad for you?

A guy idling behind the wheel of his car and looking at his phone.
What experts say about the health risks of idling in your car — and what you can do to make a difference. (Getty Images)

If you drive a car regularly, the odds are high that you'll have to sit and wait in it with the engine running at some point. The practice is known as idling, and it's common to do it during certain moments throughout the day. You may idle while waiting in a drive-through line, picking up a curbside order or dropping off the kids at school or when you're stuck in standstill traffic.

Though idling is common, it's not great for the people around your car. The U.S. Department of Energy (DOE) and Environmental Protection Agency (EPA) both advise against idling, and there are even some school initiatives against it. Idlers are also subject to a fine in some areas, including New York City, Massachusetts, Maryland, New Hampshire, New Jersey, Vermont, Hawaii and parts of California, Colorado, New York, Ohio and Utah.

But why is idling so bad, and what can happen when you do it? Doctors explain.

There are a few things that make idling a practice to avoid. It reduces your car's fuel economy, ends up costing you money and creates pollution, according to the DOE.

"It really comes down to pollution," Dr. Inderpal Randhawa, medical director of the Children’s Pulmonary Institute at MemorialCare Miller Children’s & Women’s Hospital Long Beach in Long Beach, Calif., tells Yahoo Life. Car exhaust generated by idling usually contains nitrogen oxide, sulfur oxide, ammonia and ozone. "People started paying attention to these vehicles that are just sitting there, generating pollution," he says. This can be bad for kids waiting for parents to pick them up or adults hanging outside a store. "The exhaust is coming out right at your airways and lungs," Randhawa points out.

"In small doses, it is not immediately dangerous. But it’s certainly not as healthy as fresh air," Dr. Diane Calello, medical and executive director of New Jersey Poison Information and Education System and associate professor of emergency medicine at Rutgers New Jersey Medical School, tells Yahoo Life.

Regular exposure to idling cars just isn't great for your health, Dr. Lina Mu, director of the Office of Global Health Initiatives at the University at Buffalo, in New York, tells Yahoo Life. "All those pollutants are known to be harmful," she says, noting that they can raise the risk of developing respiratory illness, cardiovascular diseases, allergies and cancer. "Those pollutants can affect children's health and development," Mu says. "Many pollutants, such as CO2, will worsen climate change."

The DOE says that it's especially important for caregivers to be aware of idling while picking kids up from school, because vehicle emissions are more concentrated near the ground, where children breathe. Poor air quality can raise the risk of asthma, and children’s lungs are more susceptible to damage than adults’ lungs are, Dr. Daniel Ganjian, a pediatrician at Providence Saint John’s Health Center in Santa Monica, Calif., tells Yahoo Life.

You're not necessarily protected when you're inside a car that's idling. "When you are inside of idling car, you are also exposed to polluted air," Mu says. "Some pollutant levels inside of the car are even higher than outside since emissions from this and surrounding vehicles in the parking lot or pick-up places can enter the car and get recirculated." (Of course, you don't want to sit inside an idling car in an enclosed space, like a garage, due to the risk of carbon monoxide poisoning.)

The DOE says that idling for more than 10 seconds — which most people do — uses more fuel and produces more emissions that contribute to smog and climate change than stopping and restarting your engine.

In general, the risks get higher the longer you sit, Calello says. "The more you idle, the more exhaust is released," she says.

If your vehicle is moving every few seconds, that's not considered idling, Randhawa adds. "It's when you're at a full stop and it's been going on for a while. If you're idling in that sense, just turn your vehicle off," he says. "If all vehicles did that, it would make a big impact."

All idling is bad — and it's worse the longer you idle for — but idling in traffic or poorly ventilated spaces like parking garages or under overpasses "can be particularly harmful," Ganjian says.

Electric vehicles don't need to be concerned about contributing to idling, Calello says. "An electric vehicle doesn’t produce exhaust, so idling indoors or outdoors is safe," she says. Hybrid vehicles shut off the engine when they're not moving, and stop-start technology is increasingly available in vehicles that aren't hybrid or electric. This also eliminates idling when the car is stopped, the DOE says.

Experts say there are a few things to keep in mind when it comes to idling. If it's not overly hot or cold, the DOE says it's best to shut off your car if you plan to be sitting in one spot for more than 10 seconds. (Just don't do this in traffic, the agency adds, since you never know when you'll need to move again.)

Since 10 seconds can be hard to gauge, Randhawa recommends using 60 seconds as your benchmark. "If you'll be there for more than a minute, turn it off," he says. "There is an old notion that turning a car on and off uses more gas, but that's not true."

Parents with a child in school can talk to administrators about the EPA's Clean School Bus program to reduce idling from school buses, or discuss ways to discourage idling at pick-up and drop-off.

"We need more people to advocate for limiting car idle time and increasing public awareness," Mu says. "While we are all concerned about air quality and climate change, this is something we can all do together to improve our environment and public health."