The Food and Drug Administration released nine new graphic warnings for cigarette packages today -- the first new labels in more than two decades. The new warnings, which depict the negative health impact of cigarettes, are required to cover at least 50 percent of every pack of cigarettes sold in the U.S. by mid-2013.

Scroll down for photos of the new warnings

"The introduction of these warnings is expected to have a significant public health impact by decreasing the number of smokers, resulting in lives saved, increased life expectancy and lower medical costs," the FDA's web site states.

The new labels replace the smaller, text-only warnings that have appeared on packages for more than 25 years and feature jarring images, including a man with a tracheotomy hole and a mouth filled with rotting teeth. They are a result of The Family Smoking Prevention and Tobacco Control Act, passed in 2009. It gave the government authority to regulate the marketing and labeling of tobacco products, which are currently responsible for nearly 450,000 deaths in the U.S. every year.

Last fall, the FDA released 36 potential warnings, which featured images like a mother blowing smoke in her baby's face and a a grey, damaged lung. The labels were made available to public comment and were the subject of some concern among experts who questioned whether they went far enough.

Joanna Cohen, PhD, director of the Institute for Global Tobacco Control at Johns Hopkins University explains that the key to effective warning labels is their ability to spark emotion, be it empathy or fear.

"What we've seen in terms of best practices globally is that you want pictures and accompanying text that elicit an emotion from the viewer," she said. "It makes people react."

She also said that the size of warning labels is important.

"Bigger is better, just because people notice [the labels] more," Cohen explained.

She thinks that the FDA's requirement of 50 percent of a pack is "respectable," though it doesn't necessarily "push the boundaries in terms of what's happening globally." (Earlier this month, Australia proposed plain packaging on all cigarette packs, meaning they would be stripped of all logos, colors and branding and just contain the product name alongside a large health warning.)

Research has shown that warning labels are effective in getting smokers to consider quitting.

A recent Centers for Disease Control study found in 13 out of 14 countries that ratified a World Health Organization treaty requiring warning labels on cigarette packs, a quarter of smokers who noticed them indicated they were considering quitting. And in six of those countries, more than half of the smokers who saw them said they were considering quitting because of the warning labels.

But intent to quit is different than actually quitting, Cohen cautioned, adding that warning labels are only part of a very serious and costly picture. Tobacco is the leading cause of preventable death in the U.S. and, according to CDC estimates, costs the economy some $200 billion per year in medical costs and lost productivity.

"Graphic images are probably not as important as raising the price [of cigarettes] or eliminating them from the work place," concurred Dr. Richard Hurt of the Mayo Clinic's Nicotine Dependence Center. "But it's a good first step."