Questions and Answers about the Electromagnetic Fields and Breast Cancer on Long Island Study
In June 2003, scientists reported findings from a population-based study to
evaluate whether exposure to electromagnetic fields (EMFs) is associated with
increased risk for breast cancer in Long Island (Nassau and Suffolk counties),
N.Y. They did not find an association between exposure to EMFs and increased
risk for breast cancer. This study, titled "Electromagnetic Fields and Breast
Cancer on Long Island: A Case-Control Study,"* is part of the Long Island
Breast Cancer Study Project (LIBCSP). Below are 11 questions and answers that
provide information about the new study, the LIBCSP as a whole, and additional
resources and references to learn more about the environment and cancer risk.
For more information about the Long Island Breast Cancer Study Project", go to
http://www.cancer.gov/cancerinfo/LIBCSP 1
1. What is the Electromagnetic Fields and Breast Cancer on Long Island Study?
The Electromagnetic Fields and Breast Cancer on Long Island Study is a
population-based case-control study conducted to evaluate whether
electromagnetic fields (EMFs) are associated with increased risk for breast
cancer among women in Nassau and Suffolk counties, N.Y. The study consisted of
576 women (cases) who were newly diagnosed with breast cancer between August 1,
1996, and June 20, 1997, and 585 women (controls) who did not have the disease.
All of the women were under 75 years of age and had resided in their current
homes in Nassau and Suffolk counties for at least 15 years before the time of
diagnosis of breast cancer (cases), or at the time they were identified
(controls) for the study. The study included a comprehensive in-home assessment
of exposure to EMFs. The research was conducted by M. Cristina Leske, M.D.,
M.P.H., of Stony Brook University, N.Y., and colleagues.
The study population was drawn from the larger study population of the Breast
Cancer and Environment on Long Island Study, which is described in an NCI Q&A;
(August 6, 2002) at http://www.cancer.gov/newscenter/LIBCSPQandA
. Women in the larger study were invited to participate in the EMF study if
they had lived in their homes for at least 15 years and were under 75 years of
age. (The number of women age 75 and older who were eligible to participate in
the study was too small to include.) Both studies are part of the Long Island
Breast Cancer Study Project (LIBCSP).
2. What is the Long Island Breast Cancer Study Project (LIBCSP)?
The Long Island Breast Cancer Study Project (LIBCSP) is an investigation of
possible environmental causes of breast cancer in Suffolk, Nassau, and
Schoharie counties, New York, and Tolland County, Conn. It is sponsored and
funded by the National Cancer Institute (NCI) and the National Institute of
Environmental Health Sciences (NIEHS). The project consists of more than 10
studies that include human population (epidemiologic) studies, a family breast
and ovarian cancer registry, and laboratory research designed to help explain
the development of breast cancer. Additional analyses from some of the research
are still ongoing, but findings have been reported from all but two of the
studies, the Breast Cancer and Environment on Long Island Follow-up Study and
the Environmental Exposures and Breast Cancer on Long Island Study. These
studies are described in Q&A; number 10. The project also includes the
development of a research tool, a Geographic Information System (GIS-H) for
Breast Cancer Studies on Long Island, which allows scientists to explore new
hypotheses on environmental risk factors for breast cancer.
3. What are electromagnetic fields (EMFs)?
EMFs are invisible areas of energy that result from the flow of electric
current. Common sources of EMFs include power lines, electrical wiring, and
appliances. While electric and magnetic fields are related, they have different
properties. The strength of both electric and magnetic fields decreases rapidly
with increased distance from the source. Because magnetic fields are not easily
shielded by most objects, as electric fields are, it is generally believed that
any possible health effects of EMFs would be due to magnetic fields, not
electric fields.
Residential magnetic fields, such as those investigated in the study, are in
the extremely low frequency (ELF) range of the electromagnetic spectrum. The
ELF range includes frequencies (measured in Hertz or cycles per second) between
3 and 3000 Hertz. The strength (magnitude) of magnetic fields is measured in
gauss (G) or tesla (T): 1 milligauss (mG) = 0.1 microtesla (mT); milli (m) = 1
thousandth; and micro(m) = 1 millionth.
4. Why were EMFs studied?
Scientists hypothesized that exposure to extremely low frequency magnetic
fields may increase breast cancer risk by affecting melatonin production (1).
Melatonin is a hormone produced in response to a lack of light by the pineal
gland, which is located at the base of the brain. Melatonin levels are
typically low during the day, and increase at night, peaking between 2 and 4
a.m. Exposure to light-at-night (for example, as in shift work) or exposure to
higher levels of magnetic fields are thought to suppress this normal nocturnal
rise in melatonin. Melatonin levels are believed to be inversely related to
estrogen levels, in that when melatonin levels are low, estrogen levels are
high and vice versa. Therefore, if light-at-night or magnetic field levels
suppress the normal nocturnal rise in melatonin, estrogen levels would
subsequently be increased. Since increased levels of estrogen are hypothesized
to increase the risk of breast cancer, this suppression of melatonin by either
light-at-night or magnetic fields could possibly increase the risk of breast
cancer.
Previous studies have shown inconsistent results linking residential and/or
occupational EMF exposure and breast cancer in women (2). Most studies did not
include direct EMF measurements at home or in the workplace. The first study to
measure EMFs directly in homes was conducted by scientists at Fred Hutchinson
Cancer Research Center, Seattle, Wash., and found no association between
residential EMF exposure and breast cancer (3).
5. How was this Long Island study conducted?
The scientists conducted a comprehensive home assessment of the study
participants' exposure to EMFs through personal interviews and by taking a
variety of EMF measurements within and around the outside of the home. The
measurement methods were based upon the results of a pilot study which is
described in another scientific paper (4). EMFs were measured in the following
ways:
24-hour measurements were taken in the bedroom and the most frequently used
room aside from the bedroom and kitchen (most lived-in room)
Spot measurements were taken at the front door, bedroom, and the most lived-in
room
Ground-current magnetic field measurements, which are electrical currents that
are sometimes present in a home's electrical grounding system (usually the
plumbing), were taken at the center of the bedroom and the most lived-in room
Wire coding (or wire mapping) in which the type of wiring surrounding a home
and the distance from this wiring was recorded and coded using the
Wertheimer-Leeper (5) and Kaune-Savitz systems (6).
The 24-hour, spot, and ground-current measurements were taken with specially
designed equipment to measure EMFs. A questionnaire was used to gather data on
residential history, housing construction history, occupational exposures,
electric appliance use, and exposure to light-at-night and shift work.
6. What were the findings?
The scientists found no association between residential exposure to EMFs and
breast cancer. Levels of in-home spot, 24-hour, ground-current measurements,
and wire codes did not differ between women who were diagnosed with breast
cancer (cases) and women who did not have the disease (controls). Further,
differences in risk were not observed between the two groups when the data were
analyzed controlling for age, family history of breast cancer, personal history
of benign (non-cancerous) breast disease, number of children (parity), and
education. The findings are reported by the research team in the July 1 issue
of the American Journal of Epidemiology (7). The authors are Dr. Leske,
Elinor R. Schoenfeld, Ph.D., Erin S. O'Leary, Ph.D., Kevin Henderson, B.S.,
Roger Grimson, Ph.D., Geoffrey C. Kabat, Ph.D., and Sang Ahnn, Ph.D., Stony
Brook University; William T. Kaune, Ph.D., EM Factors, Richland, Wash.; and
Marilie D. Gammon, Ph.D., University of North Carolina at Chapel Hill.
7. What is the significance of the study?
These findings are similar to those reported last year by scientists at Fred
Hutchinson Cancer Research Center (3). Both of these studies included a
comprehensive set of in-home measurement of EMF exposure and wire codes. This
new study led by Stony Brook University scientists included ground-current
magnetic field measurements, which were not included in the earlier study. In
addition, the study included only long-term residents, with the objective of
assessing exposures over an extended time period.
The EMF and Breast Cancer on Long Island Study had a large sample size and high
participation rates. It used the best available methods to estimate past
exposure to magnetic fields in the home. Because study participants lived in
their homes for 15 years or more, the in-home measurements are likely to be
indicators of their past exposures. Multiple methods were used to assess
in-home exposure, using various techniques and approaches. Further, the study
followed a standardized protocol with many quality control procedures.
8. Are the scientists conducting further research?
A scientific paper describing the wire coding methods will be published in the
July 15 issue of the International Journal of Exposure Analysis and
Environmental Epidemiology. A paper presenting study results on the use
of electric blankets in cases and controls will be published in the September
1, 2003, issue of Epidemiology . The scientists are analyzing data on
use of electrical appliances, shift work and light-at-night, and occupational
exposure.
9. Why was the LIBCSP conducted?
There has been a pattern of elevated mortality rates (the number of deaths per
year) for female breast cancer extending from the Mid-Atlantic through the
Northeastern states that has persisted for many years. Established risk factors
are believed to be largely responsible, such as increasing age and having a
family history of breast cancer, but the remaining reasons are unknown.
Incidence rates (the number of breast cancer cases newly diagnosed each year)
in Nassau, Suffolk, and Schoharie counties, N.Y., and in Tolland County, Conn.,
were above the United States average at the time the LIBCSP began. For this
reason, the project and other studies have been undertaken to try to learn if
there are environmental exposures that may be responsible.
Public Law 103-43, enacted in 1993, directed that NCI conduct a study of
"potential environmental and other risks contributing to the incidence of
breast cancer" in Nassau, Suffolk and Schoharie counties, N.Y., and Tolland
County, Conn. The law also stated that the study on Long Island "should include
the use of a geographic system to evaluate the current and past exposure of
individuals, including direct monitoring and cumulative estimates of exposure
to (1) contaminated drinking water; (2) sources of indoor and ambient air
pollution, including emissions from aircraft; (3) electromagnetic fields; (4)
pesticides and other toxic chemicals; (5) hazardous and municipal waste; and
(6) such other factors as the director [of NCI] determines to be appropriate."
10. What other research has been conducted as part of the LIBCSP?
Breast Cancer and the Environment on Long Island Study. This
population-based case-control study was conducted to determine if polycyclic
aromatic hydrocarbons (PAH), a pollutant caused by incomplete combustion of
various chemicals including diesel fuel and cigarette smoke, and organochlorine
compounds, chemicals found in many pesticides, are associated with increased
risk for breast cancer among women on Long Island. The scientists found that
organochlorine compounds are not associated with increased risk for breast
cancer on Long Island. Exposure to PAHs was associated with a modest increased
risk for breast cancer. This finding is consistent with a few, much smaller
epidemiologic studies and suggests the need for additional research in other
populations. The research also confirmed the presence of many of the well-known
breast cancer risk factors among the study population. These risk factors
included increasing age, having a family history of breast cancer, having a
first child at a later age, never having given birth to a child, and having
higher income. The findings were reported in 2002 and are described in an NCI
Q&A; (August 6, 2002) at http://www.cancer.gov/newscenter/LIBCSPqanda. The
principal investigator is Marilie D. Gammon, Ph.D., University of North
Carolina at Chapel Hill. (8,9)
Breast Cancer and the Environment on Long Island Follow-Up Study. Women
who were diagnosed with breast cancer and who participated in the Breast Cancer
and the Environment on Long Island Study (described above) continue to be
followed to determine whether organochlorine compounds, PAHs, and lifestyle
factors influence survival. Findings are expected about 2006. Dr. Gammon is the
principal investigator.
Epidemiology of Breast Cancer on Long Island. This hospital-based
case-control study investigated breast cancer risk in relation to levels of
organochlorine pesticide compounds in Nassau and Suffolk counties (Long Island)
and Schoharie County, N.Y. The scientists found that increased risk for breast
cancer did not appear to be associated with past exposure to organochlorine
compounds. There was no association between breast cancer risk and levels of
total pesticides or total polychlorinated biphenyls (PCBs). PCBs are a group of
chemical compounds found in coolants and lubricants in transformers,
capacitors, other electrical equipment, and some consumer products. The
principal investigator is Steven D. Stellman, Ph.D., American Health
Foundation, Valhalla, N.Y., now at Columbia University, New York. (10)
Organochlorines and Risk of Breast Cancer. This pilot hospital-based
case-control study investigated the relationship between exposure to
organochlorine compounds and risk for breast cancer in Tolland County, Conn.
Data on the Tolland County study population were included in a larger
hospital-based case-control study of women from Connecticut that did not find
an association between organochlorine compounds and increased risk for breast
cancer. The principal investigator is Tongzhang Zheng, M.D., Sc.D., Yale
University, New Haven, Conn. (11,12,13,14,15)
Reducing Barriers to Use of Breast Cancer Screening. This study
investigated whether a telephone counseling intervention aimed at women who are
known to underuse breast cancer screening can, with or without an accompanying
educational intervention for their physicians, increase use of breast cancer
screening. Women who had a previous mammogram at the start of the study and who
subsequently received telephone counseling were more likely to become regular
mammography users than women who did not receive counseling. In addition, the
findings suggested that the educational intervention for physicians is
associated with initiation of mammography use among women who have never had a
mammogram. More research with larger samples is needed to confirm this finding.
The principal investigator is Dorothy S. Lane, M.D., Ph.D., Stony Brook
University. (16,17,18,19,20)
Metropolitan New York Registry of Breast Cancer Families. The registry
is recruiting families who have a history of breast and/or ovarian cancer.
Participants are asked to contribute information, blood, and urine samples that
can be used for studies on the causes of these diseases. The registry is one of
six international registry sites funded by NCI to provide scientists a source
of information and specimens to speed their investigations into the causes of
breast cancer. Rubie Senie, Ph.D., Columbia University, is the principal
investigator. Families who are interested in participating in the registry may
call Columbia University at 1-888-METRO-08 (1-888-638-7608).
Environmental Exposures and Breast Cancer on Long Island. This
investigation is being conducted to determine whether length of residence in
close proximity to hazardous waste sites, industrial sites, or toxic release
inventory sites; prior land use (for example, farm land); and exposure to
various chemicals in drinking water may increase risk for breast cancer on Long
Island. Findings are expected to be reported in late 2003. The principal
investigator is Erin O'Leary, Ph.D., Stony Brook University.
Estrogen Metabolites as Biomarkers for Breast Cancer Risk. In this
study, investigators examined whether differences in the way women's bodies
process the natural hormone estrogen may be related to breast cancer risk.
Estrogen is metabolized by two main, competing pathways, either to
2-hydroxyestrone or to 16-alpha-hydroxyestrone. Some research has suggested
that the balance between the estrogen metabolite 16-alpha-hydroxyestrone, which
has been associated with breast cancer, and 2-hydroxyestrone, which has not,
may affect risk for the disease. The scientists found that postmenopausal women
with very low levels of the "good" metabolite (2-hydroxyestrone) relative to
the "bad" metabolite (16-alpha-hydroxyestrone) had a greatly increased risk of
breast cancer, compared to women with high levels of the "good" metabolite.
Because of the small number of study participants, further study is needed to
confirm the findings. The principal investigator is H. Leon Bradlow, Ph.D.,
Strang Cancer Prevention Laboratory, New York. (21)
Regulation of Scatter Factor Expression in Breast Cancer. This research
evaluated how a growth factor called scatter factor may regulate growth of
breast cancer. Using tissue samples from Long Island women, the scientists
found that levels of scatter factor are higher in invasive breast cancers than
in non-invasive cancers. It also causes human breast cancer cells to move
faster and to be more invasive in cell cultures. Further, the growth factor
induces breast cells to produce an enzyme that degrades tissue, thus
facilitating tumor invasion, and stimulates formation of new blood vessels,
which is essential for tumor growth and spread. The principal investigator is
Eliot M. Rosen, M.D., Ph.D., Long Island Jewish Medical Center, New Hyde Park,
N.Y. (22)
RDA Analysis of Breast Cancer . The study examined genetic changes in
breast tumor tissue from patients on Long Island using a technique called
representational difference analysis (RDA). Certain alterations in genes may be
linked to environmental exposures, and certain mutations may be characteristic
of specific exposures. The principal investigator is Michael H. Wigler, Ph.D.,
Cold Spring Harbor Laboratory, Cold Spring Harbor, N.Y. (23)
11. What is the Geographic Information System (GIS-H) for Breast Cancer Studies
on Long Island?
NCI has developed a prototype health-related geographic information system
(GIS-H) for Long Island as part of the LIBCSP. This advanced research tool
provides scientists a mechanism to investigate relationships between breast
cancer and the environment on Long Island. It also enables scientists to
estimate exposure to environmental contamination.
GISs are powerful computer systems that permit layers of information to be
superimposed and manipulated. The systems consist of hardware, software, and
data tables. The "H" in GIS-H stands for "health," because the system
potentially can be used for research on other types of cancer, and other
diseases and conditions.
The GIS-H consists of more than 80 databases that have geographic, demographic,
health, and environmental data on Nassau and Suffolk counties and, to a lesser
extent, on surrounding counties. It also has statistical and analytical tools
for scientists.
The GIS-H also will provide an internet mapping facility for the public.
Visitors will be able to see and use some of the content and features of the
GIS-H without needing special computer skills. They may choose from a list of
interactive maps available on the Web site or choose to install the ArcExplorer
mapping software on their computers. This software allows visitors to access
GIS-H map services to construct their own maps.
Information about GIS-H is available at http://www.healthgis-li.com
. The GIS-H was developed and is maintained by Titan Systems Corporation
(formerly AverStar Inc.), Vienna, Va., under a contract with NCI.
12. What additional resources are available about the possible relationship of
the environment and risk of breast cancer?
The Long Island Breast Cancer Study Project Web site: (http://epi.grants.cancer.gov/LIBCSP
).
Electric and Magnetic Fields - Research and Public Information Dissemination
Program (EMF RAPID) Web site: (http://www.niehs.nih.gov/emfrapid
).
"Cancer and the Environment." This fact sheet is a compilation of information
and resources on cancer and the environment: (http://newscenter.cancer.gov/pressreleases/LIBCSPresource.html
).
"Cancer Clusters" fact sheet. Cancer clusters are described and resources
provided for reporting suspected clusters: (http://cis.nci.nih.gov/fact/3_58.htm
).
--------------------
*Schoenfeld, ER, et al. Electromagnetic Fields and Breast Cancer on Long
Island: A Case-Control Study. American Journal of Epidemiology 158:47-58,
2003.
To view the June 25, 2003, American Journal of Epidemiology article on the
Electromagnetic Fields and Breast Cancer on Long Island study, go to
http://aje.oupjournals.org/current.shtml 2 .
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