Some of the most polluted places in the world are ports, resulting in health problems that some experts say can lead not only to respiratory problems, but cancer.

In the United States, the western state of California has the nation's toughest environmental regulations when it comes to air quality at the ports. Its actions will impact ships from around the world.

Los Angeles is not only the second-largest city in the United States, but it also ranks high for having some of the dirtiest air in the U.S.  

"We have the designation of perhaps having the worst air quality in the United States," noted Christopher Patton with the Port of Los Angeles.

The twin ports of Los Angeles and Long Beach are among the main culprits for generating pollution in the area.  Patton says in the last five years, there has been an effort to clean up the air within the two ports, and they are not the only ones.

"Even many of the Chinese, Korean and Japanese ports are looking at the same things we are because the problem is universal," added Patton.  "You have high-density population areas where you have industrial port complexes and as those populations grow and as the standard of living improves, people consume more.  You're going to have more imported and exported products and that creates an air quality problem."

Heather Tomley with the Port of Long Beach says oceangoing vessels create a significant amount of pollution.

"They are greater than 50% of the emissions that we see at the ports and they are our biggest challenge," noted Tomley.

To clean up the air, California is the only state in the U.S. to require all ships to use low-sulfur fuel when they are within 44 kilometers of the shore. A recent study by the National Oceanic and Atmospheric Administration (NOAA) found that using this type of fuel reduced harmful emissions by as much as 90 percent. But ship pilot Mark Coynes says the engines of many ships are not designed for cleaner fuel.

"It not only can potentially damage the engine, but it could actually cause operational problems," noted Coynes.

But ship engines will have to be adapted. Starting in 2012, under the International Maritime Organization's regulations, all ships within 370 kilometers of North America will have to use cleaner diesel fuel. This is already the standard when it comes to the Baltic and North Seas.

Once docked, ships traditionally continue to use diesel to power the vessels. Under California law, the most visited ports in the state are now working towards providing shore power for certain types of ships so they can plug into an electric power supply and reduce emissions. Christopher Patton says shore power can also be found in the Port of Shanghai.

"They have a very active and aggressive shore power program that they're implementing throughout all their marine terminals and they're utilizing the technology that in fact we spearheaded here at the Port of Los Angeles for container ships," said Patton.

The ports around the U.S. are also trying to reduce emissions in cargo handling equipment and trucks.  Some trucks now run on cleaner burning diesel fuel engines, while others are using compressed or liquefied natural gas.  Peter Torres' company sells trucks that run on propane.  Torres says he has suffered the effects of polluted air.

"I've been a foreman and a longshoreman for 31 years and I've known in the last 15 years, I've felt a considerably different feeling in my respiratory system in the way that I breathe and how much air I can take in and out," Torres said.

Heather Tomley with the Port of Long Beach says the hope is to get an 85 percent reduction in health risk.  To help with that goal, the ports of Los Angeles and Long Beach hope to have electric vehicles that operate in and around the port complex within the next several years.