The cell phone has become an essential business tool, but it's gotten a bad rap as far as health is concerned.

In September, the California legislature sent a bill to governor Arnold Schwarzenegger to outlaw the use of cell phones in automobiles, unless drivers use "hands-free" technology -- such as headsets or earpieces that keep their hands on the steering wheel. The state would join the ranks of New York, New Jersey, Connecticut and Washington, D.C., which have all criminalized this essential business tool. Proponents point to a body of research, including a California Highway Patrol study from 2004 which found that drivers using cell phones pressed against their ears caused accidents 25 times more than drivers using hands-free gear.

But driving is not the only concern about cell phones. In March, a study by the Swedish National Institute for Working Life found that prolonged cell phone use -- it defined heavy use as 2,000 hours or more in a lifetime -- may put people at increased risk of brain tumors. The Swedish study, which disputed some earlier studies, is the biggest study yet to cover long-term mobile phone usage, involving 2,200 cancer patients and the same number of healthy individuals.

The news might cause you to consider urging employees not to make cell calls from behind the wheel. Or, at the very least, you may want to issue employees head-sets or earpieces when purchasing cell phones for their business use.

There has been a lot of ink spent on looking at cell phone dangers -- from brain cancer to interfering with medical devices to causing accidents. Here is the fact versus the fiction about these claims:

CLAIM: Cell phones cause brain tumors.

FACT: Cell phones pass along information via airwaves, similar to the way music stations transmit their signals from a giant radio antenna. The difference is that instead of sending those signals to a radio, they are being directed toward your ear. Some scientists, such as the Swedish researchers, have found constant exposure can create cancerous brain cells. But other research has found little or no impact on tumor rates. In January, the London-based Institute of Cancer Research and several universities in Britain reported their results from a four-year study involving 966 people with brain tumors and 1,716 healthy respondents.

The U.S. Food and Drug Administration in 2003 found that radio frequency, or RF, waves sent by cell phones are different from other, more powerful currents. "Very high levels of electromagnetic energy, such as is found in X-rays and gamma rays, can ionize biological tissues," said the report. "The energy levels associated with radio frequency energy, including both radio waves and microwaves, are not great enough to cause the ionization of atoms and molecules."

So where does the truth lie? Researchers are still in the labs determining the answers. In the meantime, more neutral experts recommend using a headset to minimize exposure to RF waves. And one universal warning is to avoid so-called "electromagnetic energy blocking" products, many of which haven't been proven to work at blocking electromagnetic energy at all. In 2002, the Federal Trade Commission charged two companies, Stock Value 1 of Boca Raton, FL, and Comstar Communications of Sacramento, CA, of making false claims that their EEB products could shield people from potentially dangerous waves. The products were called "SafeTShield," "NoDanger," "WaveShield," "WaveShield 1000," and "WaveShield 2000," which you place on your cell phone's ear or mouthpiece to allegedly keep the radio waves away from your head.

CLAIM: Cell phones interfere with medical devices.

FACT: RF energy from wireless phones can interact with some electronic devices. The FDA has developed a method to test the levels of electromagnetic interference from mobile phones with cardiac pacemakers and defibrillators. It's now considered a standard test by the Association for the Advancement of Medical Instrumentation, a trade group, and manufacturers use this as a guide to make sure that these medical devices are safe from wireless phone interference.

In addition, the FDA has conducted tests on hearing aids for interference levels from cell phones. The agency helped develop a voluntary standard with the Institute of Electrical and Electronic Engineers that includes testing methods and performance requirements for hearing aides and wireless phones to ensure no interference between "compatible" phones and hearing aids.

CLAIM: Cell phones cause traffic accidents.

FACT: A New England Journal of Medicine study from 2001 found that drivers using cell phones were four times more likely to get into accidents than non-cell phone users. A 2005 study by the U.S. National Highway Traffic Safety Administration (NHTSA) found that six percent of drivers actively used hand-held phones -- roughly one million people. A different group, making up four percent, used a hands-free phone. Another recent study, published in the journal Human Factors, found that cell phone users were more likely to get into an accident than individuals who were legally drunk.

Hands-free units, now being built into higher-end cars, are universally considered safer than handheld phones. In fact, like California, a growing number of states including are banning handheld cell phone use while driving. The American Automobile Association (AAA) advises drivers to: avoid talking while behind the wheel, let voice mail pick up calls, and pull over to a safe spot if you absolutely have to take the call.

Whatever the research eventually shows, business leaders may take note of a recent study at Santa Clara Valley Medical Center in San Jose, Calif., of business people in all different types of professions that found strong evidence that use of headsets can -- at a minimum -- reduce neck, shoulder and upper back muscle tension as much as 41 percent.