Kaufman DW, Anderson TE, Issaragrisil S. Risk factors for leukemia in Thailand. Ann Hematol. 2009 Mar 18 Ahead of print

Leukemias are common worldwide. However, most of the deaths occur in developing countries where access to treatment is sparse. Leukemias are heterogeneous and may be caused by a variety of risk factors, including exposure to benzene, ionizing radiation, pesticides, cigarette smoking, and electromagnetic fields (EMF). Cellular phones may increase the risk of leukemia through exposure of the active bone marrow in the skull to EMF emitted by the phone.

To examine the relationship between the use of cellular phones, as well as other established risk factors, and adult leukemia in Thailand.

Recently diagnosed leukemia cases aged 18 and over were recruited from the largest hospital in Bangkok during the period from April 1997 through February 2003. Up to 4 controls selected from among other patients at the hospital were matched to each case on age and sex. The final study population included 180 cases and 756 controls. Information on exposure to chemicals, ionizing radiation, and EMF, a detailed history of cellular phone use, and information on lifestyle (smoking, drug use) was collected by trained nurses.

Thirty-nine percent of cases were aged 45 years or more.  Cases were slightly more likely to be in the high income category than were controls.  Cellular phone use was more common among cases (19%) than among controls (16%) and increased the odds of leukemia by 1.5 (95% CI 1.0-2.4).  Among cellular phone users, cases were more likely than controls to have owned the phone for a longer duration, had a higher median lifetime hours of use, and had a higher median hours of use per year.  This pattern was similar for all leukemia sub-types.  Relatively more cases than controls were high risk users of mobile phones, that is, they initiated calls rather than received them (7% vs. 3%), extended the antenna at least 75% of the time (6% vs. 4%), or wore metal glasses at least sometimes (7% vs. 3%).  Mobile phone users with at least one of these high risk use patterns were 1.8 (95% CI 1.1-3.2) times more likely to develop leukemia than were non-users.  Mobile phone users who subscribed to the GSM service were 2.1 (95% CI 1.1-4.1) times more likely to develop leukemia.

There was no evidence of an association between leukemia and EMF exposure from household appliances or from living close to power lines.  An association between leukemia and exposure to chemicals, including benzene and pesticides, was limited to myeloid leukemias.

Interpretation and Limitations
The overall association between cellular phone use and leukemia was small, although the risk was more substantial among users of GSM service and those with high risk use patterns.  Two previous studies have not found an increased risk of leukemia associated with cellular phone use.  In the most recent 2 years of the current study, the prevalence of cellular phone use was virtually identical in cases and controls.  In addition, the increased risk among GSM subscribers and high risk users was not further related to the amount of use, which detracts from the credibility of the findings.  Other limitations were the short overall duration of use in the study population and the quality of exposure information obtained by interview.

The current study provides no convincing evidence of an association between cell phone use and leukemia, although the data are not sufficient to exclude the possibility.



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