Health effects of cell phone use still unclear

http://article.wn.com/view/2008/07/15/Health_effects_of_cell_phone_use_still_unclear/
A definite link between cell phone use and cancer has yet to be determined
By Shari Roan - LOS ANGELES TIMESUpdated: 07/15/08 9:43 AM

Drivers who use hands-free cellular devices while driving may be doing themselves a favor in the long run.
That’s because scientists still can’t say with certainty that placing a cell phone against the head is completely safe, especially for heavy users and people who began using the devices as children. They point to lingering questions over the potential health effects from the energy emitted by the phones, specifically the long-debated risk of developing brain cancer.
“It’s fair to say that the data aren’t all in yet,” says Dr. David L. McCormick, a biologist and director of the Illinois Institute of Technology Research Institute in Chicago, who has studied the issue. “There are a small number of epidemiological studies that have suggested a possible increase in cancer risk. But comparable studies in other populations haven’t confirmed these findings.”
That’s not to say anyone should panic. Cell phones do produce a type of radiation, but it’s of the type called nonionizing radio frequency — a form of energy located on the electromagnetic spectrum. At the high end of the spectrum, ionizing radiation, such as that emitted by X-ray machines, has well-known dangers. But the weak signals released by nonionizing radio frequencies do not cause DNA damage, and there is no explanation for how such energy could cause cancer, McCormick says.
Most studies have not consistently demonstrated a link between cell phone use and cancer, including two studies conducted by the National Cancer Institute. Several other studies coordinated through the International Agency for Research on Cancer, called the Interphone studies, have also failed to show an association. Numerous laboratory studies on animals have also found no evidence that DNA is damaged by low levels of radio frequency, McCormick says.
But the sheer number of people now using cell phones and the volume of use, as well as a few studies that found a potential link between brain cancer and cell phones, have kept the safety question looming.
The National Academy of Sciences released a report in January calling for more research on cell phones and health risks. The authors concluded that many of the past studies were not conducted over a long-enough period of time to assess the risk of brain cancer, which typically develops slowly.
Nor have the studies examined the effects of cell phone use on children, whose nervous systems are still developing, or on whether the radio frequency emissions can cause other types of health problems, such as cancers elsewhere in the body or central nervous system damage that may affect learning or behavior, says Dr. Leeka Kheifets, a professor of epidemiology at the University of California, Los Angeles’ School of Public Health, who was a member of the NAS panel.
“At this point, it looks unlikely that cell phones are causing brain tumors, particularly from short-term exposures,” says Kheifets. “But we have not looked at all kinds of health outcomes yet. The focus has been on brain tumors because exposure from cell phone use is mostly to the brain. And we are just beginning some studies on brain cancer in children.”
Kheifets and researchers in Denmark recently examined cell phone use in children and found “unexpected results.” The researchers examined 13,159 Danish children born in 1997 and 1998 who are participants of a study called the Danish National Birth Cohort. The children’s mothers were surveyed during pregnancy and again when the children were 18 months old and 7 years old.
The study found that children who used cell phones, and whose mothers used cell phones during pregnancy were 80 percent more likely to have behavioral problems such as emotional symptoms, inattention, hyperactivity and problems with peers compared with children who had no cell phone exposure as fetuses or in early childhood. Children whose mothers used cell phones during pregnancy but who had no other cell phone exposure were 54 percent more likely to have behavioral problems.
The study, which will be published this month in the journal Epidemiology, is the first to find a behavioral effect and so must be interpreted with caution. But Kheifets says, “In general, children are more susceptible to environmental hazards. We have little information on cell phones, and children are using cell phones at younger ages.”
Research on children and long-term studies should provide more clarification on any health risks, says Dr. Siegal Sadetzki, an epidemiologist at Gertner Institute, Chaim Sheba Medical Center, in Israel.
Sadetzki’s research has found heavy cell phone users were at 50 percent higher risk for a parotid tumor, which arises in the salivary gland near the ear and jaw, typically where cell phones are held. Parotid tumors can be cancerous or benign. The study was significant because it tracked heavy users for more than 10 years and found a relationship between the side of the head the phone was typically placed against and where the tumor formed.
She says she doesn’t think her study, which was published in February in the American Journal of Epidemiology, contradicts previous studies that showed no cause for alarm. The research was conducted in Israel, which has a population of heavy users who were among the first to adopt cell phone technology.
“Most negative results were seen for short-term users, below 10 years of use,” she said in an e-mail interview. “It is well known that the latency period for cancer development, and certainly for brain tumor development, is longer than that. The problem is, of course, that we are dealing with a relatively new technology.”
Says Sadetzki: “I believe that the cell phone technology has a lot of advantages and is here to stay. But we, as a society, need to decide how to use it. ... I think that the precautionary principle advising the use of simple measures to lower exposure should be adopted and taken seriously.”