A new study out of Denmark suggests that cell phone use may not increase your risk of some types of noncancerous brain tumors.

Reuters reported this week on a study published in the American Journal of Epidemiology that found people who used a cell phone for 11 to 15 years were no more likely to develop an acoustic neuroma, a noncancerous brain tumor, than people who have been using cell phones for either a shorter period of time or who have never used a cell phone.

Even though acoustic neuroma, or vestibular schwannoma, as it is also known, is noncancerous, it is important to the study because such tumors typically grow in the area of the brain where more energy is emitted from the cell phone and absorbed by humans, Dr. Joachim Schuz, who is with the World Health Organization's International Agency for Research on Cancer (IARC) and led the new study, told Reuters.

Apparently, it makes sense that if cell phone radiation caused tumor growth in humans, that this particular tumor might be found more often in people using cell phones.

But Schuz's team didn't find an increased risk of the tumors when they studied data for nearly 3 million Danish adults, of which 800 had been diagnosed with acoustic neuroma between 1998 and 2006. Shuz also told Reuters that the study also found no increased risk among people who used their cell phones for the longest period of time, which was at least 11 years. Of the people who had tumors, there was no indication that cell phone use increased the size of the tumors, he said. Also, it did not appear that people developed their tumors on their right side of their head, where most people hold their cell phone.

Although the study did not find an increased risk, it doesn't necessarily mean that cell phones are safe, Schuz warned. These tumors are very slow growing and can take decades to manifest. Most people involved in the study had only been using cell phones since the 1990s. So its conceivable that effects may manifest years from now. And of course, there are also other types of brain tumors and brain cancer.

Much of the scientific research on the use of cell phone use and radiation has been inconclusive. Epidemiological studies, including the World Health Organization's decade long Interphone study, have generally shown no relation between cell phone use and brain cancer. But the data from the Interphone study is still being examined, and more reports are expected using this data.

Meanwhile, biological studies on animals have suggested that radiation at the frequencies used for cell phone can have an effect on cells. And there has even been some research to suggest that changes can occur to the human brain when exposed to cell phone radiation. Earlier this year, researchers published a paper that examined scans of the brain to measure brain activity. They discovered that exposure to cell phone radiation excited certain areas of the brain. But they couldn't conclude whether this had any adverse health effects on humans.

In May, the IARC categorized cell phone usage as a possible carcinogen, putting it in the same category as lead, gasoline engine exhaust, and chloroform.

The IARC had examined published studies as it considered how to classify cell phone radiation. Schuz, who is affiliated with the IARC, said the current study was considered in the new classification. The IARC said that it came to its conclusion because there is not enough evidence to definitively say that cell phones do not cause cancer. Still, the agency has also pointed out that it has not found any direct correlation between cell phone use and cancer.

Researchers at the IARC say that more studies are needed to finally determine the safety of cell phones.

For more information on this topic, check out CNET's special report, which examines the research, discusses ways to limit exposure, and shows cities and states around the country that are passing laws to inform and protect consumers from possible risks.