When Elliot Caroom moved to New York City last fall, among his worries were finding a place to live and, perhaps, running into the occasional person who might do "disturbing" things on the subway. Now, a new and more mechanical menace towers above all others.
"I didn't really think about it until a few crane incidents a few months back," Caroom said. "I'm naturally somewhat paranoid, so I started to notice more cranes, glancing upward, and at this point, it has become more serious."
Although he looks up "nervously" each time he passes by a crane, the 26-year-old graduate student acknowledges the irrationality of it all, adding that there's probably a stronger likelihood of being involved in a plane crash than a crane accident.
Still, psychologists find that such fears are fairly common, since certain aspects of big city life tend to trigger deeper anxieties.
Fred Newman, director of the White Plains Anxiety and Phobia Treatment Center, says dangerous situations that may be dramatic, involve many people at once or invoke a sense of being trapped, and are perceived by many to be "much scarier" than those situations that don't.
"Bridges, tunnels, closed-in spaces, like elevators, and large crowds are the type of places where people would be more likely to feel that way, because catastrophic things can happen," Newman said.
And as the population of a big city grows, so does the strain on its infrastructure.
"The cranes are there because they're expanding housing and office space, so demands on older systems are increasing," said Patrick Natale, executive director of the American Society of Civil Engineers.
Recently, as the wear and tear of old infrastructures start to show, these fears are starting to be realized.
In July 2007, an 83-year-old steam pipe burst in the busy midtown section of Manhattan. In the aftermath of the explosion, which killed one and injured 45 people, concerns surfaced about the condition of a water infrastructure system that has been creaking along since 1882.
A month later, the I-35W River Bridge in Minnesota collapsed, leaving 13 dead and more than 100 injured. The bridge, which government inspectors found to be "structurally deficient" in 1990, and again in 2005, had been slated to receive a steel reinforcement upgrade, but the project was scrapped in favor of periodic safety inspections.
"Our approach in this country to these problems has been a patch-and-pray mentality -- let's patch it up and pray that it lasts, instead of a good strong plan to make it right," said Natale, adding that "structures will break" if cities continue to operate this way.
In 2005, the American Society of Civil Engineers reported that more than a quarter of U.S. bridges are "structurally deficient." The group also estimated that $1.6 trillion would be needed over the span of five years to bring the nation's water infrastructure to a level where it can hold up to the demands of modern societies.
Brian Mergelas, a water pipe expert, points out that many threats to big cities, posed by aging water infrastructure, might not be as dramatic as a pipe explosion, but they are no less hazardous.
Sinkholes, for instance, can happen when a broken pipe gradually sucks away soil, weakening land to the point of collapse. Such sudden urban pits have been known to swallow cars, large trucks and pedestrians.
On stormy days, rainwater can enter a damaged pipe, causing sewage to overflow. Geysers have also sprouted at the site of burst water mains.
"High-risk pipes tend to be in your urban environments," Mergelas said. "You get more traffic and external stresses on pipes in city areas than in rural areas. So, you get that, compounded with the effects of deteriorating pipes."
He doesn't think, however, that massive financial investments are required to keep old pipe systems in safe working order.
"Instead of replacing everything, why not just find and fix the areas of the system that are breaking down?" he said.
His company, based in Toronto, has developed an acoustic sensor that can detect leaks by dropping it into working water pipes. This technology, he believes, would not only be cheaper, but just as effective in keeping pipes from bursting open.
Another street hazard responsible for serious injuries and millions in damages every year are potholes. Constant freezing and thawing of city streets have left big cities all across America pocked with these costly holes-in-the-ground.
The city of Toronto, for instance, spends roughly $4 million annually to repair about 165,000 potholes. But, standing by as the annoying holes crop up can prove to be even pricier.
Last month, an 83-year-old Bronx, N.Y., woman who suffered a leg injury when she stepped into a pothole, sued the city for negligence and was awarded $3.8 million in damages.
"Pothole injuries can be serious," said Stephan Peskin, an attorney who specializes in pothole injuries. "Even a slightly raised curb can end up [causing] a fractured ankle."
A previous ABC News report found New York to be among the 10 major urban areas with the worst pothole problems.
Peskin, who directs the Big Apple Pothole and Sidewalk Protection Committee in New York City, sees the city's pothole troubles primarily as a result of neglect.
"Instead of making a repair and doing it correctly and immediately, they let it fester," he added.
While watching your step may help you avoid potential pitfalls on city streets, toxins in the air are nearly unavoidable. A study conducted by researchers at UCLA suggests that those who live, work or travel close to a major freeway or busy intersection may be exposing themselves to 30 times more air toxins than normal.
Even exercising, an activity that's good for your health, can have you sucking hazardous wind.
To avoid the high levels of pollution near streets, Dr. Donald G. Crystal, a pulmonary expert at Cornell University, recommends jogging or bicycling in the early mornings and late in the evenings, or to take your workout indoors.
But while studies consistently suggest that city dwellers face more health risks stemming from air pollution, Crystal says that big city life can far outweigh any potential health consequences.
"New York City is a great city to live in. We have to take into account what we want in terms of lifestyle," Crystal said. "I mean, we can all live in Antarctica and there would be no pollution, right?"