Magnetic Fields and Leukemia
http://www.100md.com
《新英格兰医药杂志》
To the Editor: In their review of acute lymphoblastic leukemia, Pui et al. (April 8 issue)1 discuss environmental factors that may interact with a genetic disposition to cause the disease. The authors claim that "exposure to residential magnetic fields has largely been excluded as an instigating factor" and cite one large study2 in support of this statement. However, they overlook two independent meta-analyses3,4 that showed an association, with a doubling of the risk of childhood leukemia with household exposures to magnetic fields of 4.0 mG (0.4 μT) or higher. Subsequently, the International Agency for Research on Cancer classified 50- or 60-Hz magnetic fields as a group 2B carcinogen — that is, an agent considered to be possibly carcinogenic in humans.5 The possible role of magnetic fields in childhood leukemia should not be dismissed, given the epidemiologic evidence, the subtlety of gene–environment interactions, and the scope for prevention with the use of relatively simple electrical-engineering techniques to minimize field exposures.
Bruck Hocking, M.B., B.S.
9 Tyrone St.
Camberwell 3124, Australia
bruhoc@connexus.net.au
References
Pui C-H, Relling MV, Downing JR. Acute lymphoblastic leukemia. N Engl J Med 2004;350:1535-1548.
UK Childhood Cancer Study Investigators. Childhood cancer and residential proximity to power lines. Br J Cancer 2000;83:1573-1580.
Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh MA. A pooled analysis of magnetic fields, wire codes, and childhood leukemia. Epidemiology 2000;11:624-634.
Ahlbom A, Day N, Feychting M, et al. A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer 2000;83:692-698.
Static and extremely low-frequency (ELF) electric and magnetic fields. Lyon, France: International Agency for Research on Cancer, March 2002. (Accessed June 11, 2004, at http://193.51.164.11/htdocs/monographs/vol80/80.html.)
The authors reply: Extensive studies in animals and laboratory studies have failed to support an etiologic role of magnetic fields in leukemogenesis.1 The public concern is prompted by the ubiquitous nature of the exposure, which has also posed a methodologic challenge, in that it is difficult to find an unexposed comparison population. Large studies from the United States, the United Kingdom, Canada, and New Zealand have provided convincing data showing that magnetic-field exposure is not associated with an increased risk of childhood leukemia.2,3,4,5 Dr. Hocking correctly points out that the results of two meta-analyses suggest that there is a significant risk of leukemia at the highest exposure level (i.e., 0.4 μT or higher). However, these analyses could not account for potential measurement errors or for selection and publication biases. Moreover, it should be noted that even if the association is real, the proportion of the population exposed to such high levels is extremely small (only approximately 1 percent of children with leukemia were in this category, as noted in the meta-analyses). Thus, the attributable risk would be negligible.
Ching-Hon Pui, M.D.
Mary V. Relling, Pharm.D.
James R. Downing, M.D.
St. Jude Children's Research Hospital
Memphis, TN 38015
ching-hon.pui@stjude.org
References
Portier CJ, Wolfe MS, eds. Assessment of health effects from exposure to power-line frequency electric and magnetic fields: Working Group report. Research Triangle Park, N.C.: National Institute of Environmental Health Sciences, 1998. (NIH publication no. 98-3981.)
Linet MS, Hatch EE, Kleinerman RA, et al. Residential exposure to magnetic fields and acute lymphoblastic leukemia in children. N Engl J Med 1997;337:1-7.
UK Childhood Cancer Study Investigators. Childhood cancer and residential proximity to power lines. Br J Cancer 2000;83:1573-1580.
McBride ML, Gallagher RP, Theirault G, et al. Power-frequency electric and magnetic fields and risk of childhood leukemia in Canada. Am J Epidemiol 1999;149:831-842. [Erratum, Am J Epidemiol 1999;150:223.]
Dockerty JD, Elwood JM, Skegg DC, Herbison GP. Electromagnetic field exposures and childhood leukaemia in New Zealand. Lancet 1999;354:1967-1968.
Bruck Hocking, M.B., B.S.
9 Tyrone St.
Camberwell 3124, Australia
bruhoc@connexus.net.au
References
Pui C-H, Relling MV, Downing JR. Acute lymphoblastic leukemia. N Engl J Med 2004;350:1535-1548.
UK Childhood Cancer Study Investigators. Childhood cancer and residential proximity to power lines. Br J Cancer 2000;83:1573-1580.
Greenland S, Sheppard AR, Kaune WT, Poole C, Kelsh MA. A pooled analysis of magnetic fields, wire codes, and childhood leukemia. Epidemiology 2000;11:624-634.
Ahlbom A, Day N, Feychting M, et al. A pooled analysis of magnetic fields and childhood leukaemia. Br J Cancer 2000;83:692-698.
Static and extremely low-frequency (ELF) electric and magnetic fields. Lyon, France: International Agency for Research on Cancer, March 2002. (Accessed June 11, 2004, at http://193.51.164.11/htdocs/monographs/vol80/80.html.)
The authors reply: Extensive studies in animals and laboratory studies have failed to support an etiologic role of magnetic fields in leukemogenesis.1 The public concern is prompted by the ubiquitous nature of the exposure, which has also posed a methodologic challenge, in that it is difficult to find an unexposed comparison population. Large studies from the United States, the United Kingdom, Canada, and New Zealand have provided convincing data showing that magnetic-field exposure is not associated with an increased risk of childhood leukemia.2,3,4,5 Dr. Hocking correctly points out that the results of two meta-analyses suggest that there is a significant risk of leukemia at the highest exposure level (i.e., 0.4 μT or higher). However, these analyses could not account for potential measurement errors or for selection and publication biases. Moreover, it should be noted that even if the association is real, the proportion of the population exposed to such high levels is extremely small (only approximately 1 percent of children with leukemia were in this category, as noted in the meta-analyses). Thus, the attributable risk would be negligible.
Ching-Hon Pui, M.D.
Mary V. Relling, Pharm.D.
James R. Downing, M.D.
St. Jude Children's Research Hospital
Memphis, TN 38015
ching-hon.pui@stjude.org
References
Portier CJ, Wolfe MS, eds. Assessment of health effects from exposure to power-line frequency electric and magnetic fields: Working Group report. Research Triangle Park, N.C.: National Institute of Environmental Health Sciences, 1998. (NIH publication no. 98-3981.)
Linet MS, Hatch EE, Kleinerman RA, et al. Residential exposure to magnetic fields and acute lymphoblastic leukemia in children. N Engl J Med 1997;337:1-7.
UK Childhood Cancer Study Investigators. Childhood cancer and residential proximity to power lines. Br J Cancer 2000;83:1573-1580.
McBride ML, Gallagher RP, Theirault G, et al. Power-frequency electric and magnetic fields and risk of childhood leukemia in Canada. Am J Epidemiol 1999;149:831-842. [Erratum, Am J Epidemiol 1999;150:223.]
Dockerty JD, Elwood JM, Skegg DC, Herbison GP. Electromagnetic field exposures and childhood leukaemia in New Zealand. Lancet 1999;354:1967-1968.