For female breast cancer, some early epidemiological studies suggested a risk for magnetic fields.
Then, in the early 2000s, three large and well-conducted studies of residential exposure were published, with uniformly negative findings. Two large studies of occupational exposure were also largely negative.
This led authoritative review groups to conclude that we could now have some confidence that magnetic fields do not cause breast cancer.
Studies on residental exposure
Three early studies were Wertheimer et al 1982, McDowall et al 1986, and Schreiber et al 1993. Of these, certainly Wertheimer et al suggested an association (for pre-menopausal women).
These were followed up by three large, thorough studies in the USA and one in Norway. The three US studies were uniformly negative and the Norwegian study largely so. These studies were (see also the abstracts):
Davis et al 2002
- Conducted in Seattle
- approximately 800 cases
- exposure assessment by 48 hour measurements
- Odds ratio per 0.1 µT exposure: 1.04 (95% confidence interval 0.97-1.12)
London et al 2003
- Conducted in Los Angeles
- approximately 700 cases (350 with measurements)
- exposure assessment by 7 day measurement
- Odds ratio per 0.1 µT exposure for night-time exposure: 1.0 (95% confidence interval 0.94-1.07)
Schoenfeld et al 2003
- Conducted in Long island
- approximately 600 cases
- exposure assessment by 24-hour measurement
- Odds ratio for exposure >0.172 µT: 0.97 (95% confidence interval 0.69-1.4)
Kliukiens et al 2004
- Conducted in Norway
- approximately 2000 cases
- exposure assessment by calculated field from high-voltage power lines plus occupational exposure
- Odds ratio for combined residential and occupational exposure: 1.3 (95% confidence interval 0.8-2.1)
Note that this is only a summary, most of the studies looked at risks in different subgroups (such as women of different ages) and for different measures of exposure (such as nighttime only or 24 hour).
Studies on occupational exposure
With studies of occupational exposure, there is a similar pattern. Some of the earlier studies suggested risks, but later, larger studies with better methodologies have been more negative.
The earlier studies were reviewed by Kheifets and Matkin 1999. The two more recent studies are Loomis et al 1994 (in the USA) and Forssen et al 2005 (in Sweden).
Conclusions of review groups
The 2004 NRPB advice on limiting exposures concludes:
“There is no clear evidence of a carcinogenic effect of ELF EMFs in adults…”
The accompanying review of the scientific evidence gives more detail, including the following statement:
“Also, studies of breast cancer and residential EMF exposures, based on measurements in the home, have generally not shown associations…” More on NRPB
The International Agency for Research on Cancer (IARC) is an agency of the World Health Organisation. Its Unit of Carcinogen Identification and Evaluation has, since 1972, periodically published Monographs which assess the evidence that various agents are carcinogenic and classify the agents accordingly. In June 2001, a Working Group met to consider static and extremely-low-frequency electric and magnetic fields. The complete results have been published as Monograph number 80. Power-frequency magnetic fields were classified as “possibly carcinogenic”. This was on the basis of “limited” evidence from humans concerning childhood leukaemia. For all other cancer types including all adult cancers, the classification was “inadequate” evidence from humans and “inadequate” evidence from animals.
A major review of epidemiology by ICNIRP published in 2001 concluded:
"The totality of evidence linking EMFs to breast cancer, in men or women, remains weak." More on ICNIRP
SCENIHR is the European Commission's Scientific Committee on Emerging and Newly Identified Health Risks. In their opinion on EMFs in 2007 they stated about breast cancer in particular:
"Breast cancer caught particular interest because of experimental results suggesting that melatonin synthesis was related to ELF field exposure and because melatonin might play a role in the development of breast cancer. Several studies also reported an increased breast cancer risk among subjects with elevated ELF exposure. However, later big and well controlled studies have been entirely negative and the hypothesis of a link between ELF field exposure and breast cancer risk is essentially written off (Forssen et al. 2005)." more on SCENIHR
View of WHO
The WHO Environmental Health Criteria Monograph published in 2007 concluded:
"Subsequent to the IARC monograph a number of reports have been published concerning the risk of female breast cancer in adults associated with ELF magnetic field exposure. These studies are larger than the previous ones and less susceptible to bias, and overall are negative. With these studies, the evidence for an association between ELF magnetic field exposure and the risk of female breast cancer is weakened considerably and does not support an association of this kind." More on the WHO Monograph
Some facts and figures on breast cancer
The following table was taken from CRUK's website:
|Breast cancer - UK
Number of new cases
Rate per 100,000 population
Number of deaths
Rate per 100,000 population
Five-year survival rate
Ten-year survival rate
As with many cancers, science evolves over the years, and there is never complete agreement on which agents are risk factors for breast cancer and which are not. But there is general agreement that, among other factors:
- alcohol increases the risk
- a lower age of first childbirth lowers the risk, and conversely never having had a child increases the risk
- having more children lowers the risk
- breastfeeding lowers the risk
- shiftwork involving circadian disruption (i.e. expoosure to light at night) probably increases the risk
Overall, the risk of breast cancer increases with increasing socioeconomic status.