Collection of Internet/Collection of Internet.iso/faq/sci/powerlin/part3

Text File | 1994-03-27 | 27KB | 539 lines

Path: bloom-beacon.mit.edu!gatech!howland.reston.ans.net!news.moneng.mei.com!uwm.edu!post.its.mcw.edu!admin-one.radbio.mcw.edu!user
From: [e-mail] (John Moulder)
Newsgroups: sci.med.physics,sci.answers,news.answers
Subject: Powerlines and Cancer FAQs (3 of 4)
Supersedes: <[e-mail]>
Followup-To: sci.med.physics
Date: 27 Mar 1994 19:57:21 GMT
Organization: Medical College of Wisconsin
Lines: 516
Approved: [e-mail]
Distribution: world
Expires: 30 April 1994 00:00:00 GMT
Message-ID: <[e-mail]>
References: <[e-mail]>
Reply-To: [e-mail] (John Moulder)
NNTP-Posting-Host: admin-one.radbio.mcw.edu
Summary: Q&As on the connection between powerlines, electrical
  occupations and cancer (continued)
Keywords: powerlines, magnetic fields, cancer, EMF, non-ionizing
  radiation, FAQ
Xref: bloom-beacon.mit.edu sci.med.physics:1308 sci.answers:1018 news.answers:16897

Archive-name: powerlines-cancer-FAQ/part3
Last-modified: 1994/3/27
Version: 2.4

FAQs on Power-Frequency Fields and Cancer (part 3 of 4)

26) What are some good overview articles?

There really no up-to-date reviews of power-frequency fields and human
health.  The reviews by Davis et al [A2], Theriault [F3] and Doll et al
[B5] are good, but were published before many of the important
epidemiological and laboratory studies were available.

27) Are there exposure guidelines for power-frequency fields?

Yes, a number of governmental and professional organizations have developed
exposure guidelines.  These guidelines are based on keeping the body
currents induced by power-frequency EM fields to a level below the
naturally-occurring fields (Question 8).  The most generally relevant are:

- National Radiation Protection Board (UK) [M5]:
  50 Hz electrical field: 12 kV/m
  60 Hz electrical field: 10 kV/m
  50 Hz magnetic field: 1.6 mT (16 G)
  60 Hz magnetic field: 1.33 mT (13.3 G)

- American Conference of Governmental Industrial Hygienists [M6]:
  At 60 Hz: 1 mT (10 G); 0.1 mT (1 G) for pacemaker wearers

- International Commission on Non-Ionizing Radiation Protection [M7]
  Magnetic field
     24 hr general public: 0.1 mT = 1 G
     Short-term general public: 1 mT = 10 G
     Occupational continuous: 0.5 mT = 5 G
     Occupational short-term: 5 mT = 50 G
  EElectrical field
     24 hr general public: 5 kV/m
     Short-term general public: 10 kV/m
     Occupational continuous: 10 kV/m
     Occupational short-term: 30 kV/m

28) What effect do powerlines have on property values?

There is very little hard data on this issue.  There is anecdotal evidence
and on-going litigation (Wall Street Journal, Dec 9, 1993).  There have
been "comparable property" studies, but any studies done prior to about
1991 (when London et al [C10] was published) would be irrelevant.  One
comparable value study has been published recently [L3], and another has
been presented at a meeting [L4]. Neither study shows hard evidence for an
impact of power lines on property values.  However, both studies indicate
that many owners think that there will be an impact, particularly if
concerns about health effects become widespread.

It appears possible that the presence of obvious transmission lines or
substations will adversely affect property values if there has been recent
local publicity about health concerns of property value concerns.  It would
appear less unlikely that the presence of "high current configuration"
distribution lines of the type correlated with childhood cancer in the US
studies [C1,C6,C10] would affect property values, since few people would
recognize their existence. If buyers start requesting magnetic field
measurements, no telling what will happen, particularly since measurements
are difficult to do (Questions 29 & 30), and even more difficult to
interpret (Question 14).

29) What equipment do you need to measure power-frequency magnetic fields?

Power-frequency fields are measured with a calibrated gauss meter.  The
meters used by environmental health professionals are too expensive for
"home" use.

A unit suitable for home use should meet the following criteria:
- A reasonable degree of accuracy and precision, plus/minus 20% seems
reasonable for home use.
- True RMS detection, otherwise readings might be exaggerated if the
waveform is non-sinusoidal.
- Tailored frequency response, because if the unit is too broadband, higher
frequency fields from VDTs, TVs, etc. may confound the measurements.
- Correct response to overload; if the unit is subjected to a very strong
field, it should peg, not just give random readings.
- The presence of a strong electrical field should not affect the
magnetic field measurement.
Meters meeting these requirements are quite expensive, $600 would probably
be the bare minimum.  These meters are not suitable for the non-technically
trained.

There is an understandable reluctance to recommend any unit with unknown
characteristics to a person whose technical abilities are also unknown, and
no peer-reviewed articles on inexpensive instruments appear to be
available.  The suggestions that one wind a coil and use headphones or a
high impedance multimeter are misguided.  A clever physicist or engineer
can anticipate and correct for nonlinearities and interferences, but for
the average person, even one technically trained, this is unreasonable.

30) How are power-frequency magnetic fields measured?

Measurements must be done with a calibrated gauss meter (Question 29) in
multiple locations over a substantial period of time, because there are
large variations in fields over space and time.

Fortunately, the magnetic field is far easier to measure than the
electrical field. This is because the presence of conductive objects
(including the measurer's body) distorts the electrical field and makes
meaningful measurements difficult. Not so for the magnetic field.

It is important for the person who is making the evaluation to understand
the difference between an emission and exposure. This may seem obvious, but
many people, including some very smart physical scientists, stick an
instrument right up to the source and compare that number with an exposure
standard.

If the instrument is not isotropic, measurement technique must compensate
for this.

In the case of power distribution line and transformer fields, the magnetic
fields will probably vary considerably over time, as they are proportional
to the current in the system.  A reasonable characterization needs to be
done over time, with anticipated and actual electricity usage factored in.
It may seem to be as simple as walking in and reading the meter, but it's
not.

------

Annotated Bibliography

A) Recent Reviews of the Biological and Health Effects of Power-Frequency
Fields

A1) Electromagnetic field health effects, Connecticut Academy of Science
and Engineering, Hartford, CT, 1992.
  "Absolute proof of the occurrence of adverse effects of ELF fields at
prevailing magnitudes cannot be found in the available evidence, and the
same evidence does not permit a judgment that adverse effects could not
occur . . .If adverse health effects from residential magnetic field
exposure exist, they are not likely to make a large contribution.╙

A2) JG Davis et al: Health Effects of Low-Frequency Electric and Magnetic
Fields. Oak Ridge Associated Universities, 1992.
  "This review indicates that there is no convincing evidence in the
published literature to support the contention that exposure to extremely
low-frequency electric and magnetic fields generated by sources such as
household appliances, video display terminals, and local power lines are
demonstrable health hazards.╙

A3) JI Aunon et al: Investigations in power-frequency EMF and its risk to
health: A review of the scientific literature, Universities Consortium on
Electromagnetic Fields, 1992.
  "the conclusions from this review highlights the absence of health
effects directly related to 60 Hz alternating current EMF on humans."

A4) PA Buffler et al: Health effects of exposure to powerline-frequency
electric and magnetic fields, Public Utility Commission of Texas, Austin,
1992.
  "no conclusive evidence to suggest that EMF due to electric power
transmission lines poses a human health hazard."

A5) JA Dennis et al: Human Health and Exposure to Electromagnetic Radiation
(NRPB-R241), National Radiological Protection Board, Chilton, 1993.
  "the bulk of the evidence points to there being no effects at levels to
which people are normally exposed".

A6) P Guenel & J Lellouch: [Synthesis of the literature on health effects
from very low frequency electric and magnetic fields], National Institute
of Health and Medical Research (INSERM), Paris, 1993.
  "laboratory studies have never shown any carcinogenic effect [but] the
epidemiological results presently available do not permit exclusion of a
role for magnetic fields in the incidence of leukemia, particularly in
children... The effect of magnetic fields on human health remains a
research problem.  It will only become a public health problem if definite
effects are confirmed."

A7) J. Roucayrol: [Report on extremely low-frequency electromagnetic fields
and health]. Bull Acad Nat Med 177:1031-1040, 1993.
  "There is no conclusive evidence linking EMF to reproductive and
teratogenic effects, and/or that EMF has a role in the initiation,
promotion or progression of certain cancers, even though some data cannot
exclude this possibility. . . reported associations between EMF and certain
pathologies like leukemia and other childhood and adult cancers cannot be
supported by current epidemiological data."

B) Reviews of the Epidemiology of Exposure to Power-Frequency Fields

B1) DA Savitz & EE Calle: Leukemia and occupational exposure to EM fields:
Review of epidemiological studies. J Occup Med 29:47-51, 1987.
  Review of occupational exposures and leukemia, showing a small but
significant excess of leukemia in electrical occupations.

B2) M Coleman & V Beral: A review of epidemiological studies of the health
effects of living near or working with electrical generation and
transmission equipment. Int J Epidem 17:1-13, 1988.
  Review of both occupational and residential studies, including
meta-analysis showing a small but significant excess of leukemia in
electrical occupations.

B3) D Trichopoulos, Epidemiological studies of cancer and extremely
low-frequency electric and magnetic field exposures, In: Health effects of
low-frequency electric and magnetic fields, JG Davis et al, editors, Oak
Ridge Assoc Univer, Oak Ridge, pp. V1-V58, 1992.
  Meta-analysis of occupational exposure studies indicating small but
statistically significant relative risks for leukemia and brain cancer.

B4) G.B. Hutchison: Cancer and exposure to electric power. Health Environ
Digest 6:1-4, 1992.
  Meta-analysis of residential exposure studies shows a significant excess
for childhood brain cancer, but not for childhood leukemia or lymphoma.
Analysis also shows an excess of leukemia and brain cancer in electrical
occupations, but no significant excess of lymphoma or overall cancer.

B5) R Doll et al, Electromagnetic Fields and the Risk of Cancer, NRPB,
Chilton, 1992.
  Includes a meta-analysis of the childhood cancer data.  For leukemia, the
analysis shows a significant elevation when wirecodes are used to assess
exposure, but not when distances or measured fields are used.  For brain
cancer, the analysis shows a significant elevation when wirecodes or
distance are used to assess exposure, but not when measured fields are
used.  For all childhood cancer the analysis shows a significant elevation
when wirecodes or measurements are used to assess exposure, but not when
distance is used.

B6) A Ahlbom et al: Electromagnetic fields and childhood cancer. Lancet
343:1295-1296, 1993.
  Pooled analysis of the Scandinavian childhood cancer studies indicates
that if calculated historic power-line fields are used as a measure of
exposure, a small but statistically significant increase is seen in the
incidence of leukemia, but no statistically significant increase is seen in
the incidence of CNS cancer, lymphoma, or overall cancer.

C) Epidemiology of Residential Exposure to Power-Frequency Fields

C1) N Wertheimer & E Leeper: Electrical wiring configurations and childhood
cancer. Am J Epidem 109:273-284, 1979.
  Case-control study of childhood leukemia and brain cancer using type of
powerlines (wirecodes) as an index of exposure.  A significant excess of
leukemia and brain cancer were reported.

C2) N Wertheimer & E Leeper: Adult cancer related to electrical wires near
the home. Int J Epidem 11:345-355, 1982.
  Case-control study of adult cancer.  Significant excess reported for
total cancer and brain cancer, but not for leukemia.

C3) JP Fulton et al: Electrical wiring configurations and childhood
leukemia in Rhode Island. Am J Epidem 111:292-296, 1980.
  Case-control study using wire-dose as an index of exposure.  No excess of
child leukemia found.

C4) ME McDowall: Mortality of persons resident in the vicinity of
electrical transmission facilities. Br J Cancer 53:271-279, 1986.
  Standard mortality ratio study using proximity to lines as a measure of
exposure.  No excess seen for total cancer or for leukemia in adults.

C5) L Tomenius: 50-Hz electromagnetic environment and the incidence of
childhood tumors in Stockholm County. BEM 7:191-207, 1986.
  Case-control study of childhood cancer using proximity to electrical
equipment as indices of exposure.  Proximity to 200 kV lines was associated
with significant excess of total cancer, but proximity to other types of
electrical equipment carried no significant excess risk.  No significant
excess of leukemia or brain cancer for any index of exposure.

C6) DA Savitz et al: Case-control study of childhood cancer and exposure to
60-Hz magnetic fields. Am J Epidem 128:21-38, 1988.
  Case-control study of childhood leukemia and brain cancer in Denver,
using measurements and wirecodes as indices of exposure.  Possibly
significant excess of leukemia for high-current-configuration wirecodes,
but no excess incidence for measured fields.  Significant excess of brain
cancer for high-current-configuration wirecodes, but no excess incidence
for measured fields.

C7) RK Severson et al: Acute nonlymphocytic leukemia and residential
exposure to power-frequency magnetic fields. Am J Epidem 128:10-20, 1988.
  Case-control study of childhood leukemia in Washington state, using
measurements and wirecodes as indices of exposure.  No excess leukemia for
wirecode or measured fields.

C8) MP Coleman et al: Leukemia and residence near electricity transmission
equipment: a case-control study. Br J Cancer 60:793-798, 1989.
  Case-control study of childhood and adult leukemia, using proximity to
powerlines and transformers as an exposure index.  No significant excess of
leukemia was found.

C9) A Myers et al: Childhood cancer and overhead powerlines: a case-control
study. Br J Cancer 62:1008-1014, 1990.
  Case-control study of childhood and adult leukemia, using proximity to
powerlines as an exposure index.  No significant excess of leukemia, solid
tumors or all cancer was found.

C10) SJ London et al: Exposure to residential electric and magnetic fields
and risk of childhood leukemia. Am J Epidem 134:923-937, 1991.
  Case-control study of childhood leukemia in Los Angeles, using
measurements and wirecodes as indices of exposure.  Significant excess of
leukemia for high current configuration wirecodes, but no excess risk for
measured fields.

C11) JHAM Youngson et al: A case/control study of adult haematological
malignancies in relation to overhead powerlines. Br J Cancer 63:977-985,
1991.
  Case-control study of adult leukemia and lymphoma using proximity to
powerlines and estimated fields as measures of exposure.  No significant
excess of cancer found.

C12) M Feychting & A Ahlbom: [Cancer and magnetic fields in persons living
close to high voltage power lines in Sweden]. Lèkartidningen 89:4371-4374,
1992.
  Case-control study of everyone who lived within 1000 feet of high-voltage
powerlines; contains material on adult exposure not in the 1993
publication.  No increased leukemia or brain cancer was found for adults
when exposure was based on measured fields, distance from power lines or
retrospective field calculations.

C13) JM Peters et al: Exposure to residential electric and magnetic fields
and risk of childhood leukemia. Rad Res 133:131-132, 1993.
  Discussion of the implications of finding a correlation of cancer with
wire-codes, but not with measured fields.  Possibilities:
- There is a true etiological association, but there is a methodological
bias in the measurement technique
- There is a true etiological association, but average and/or spot fields
are not the correct exposure metric
- Selection bias in the control group
- A confounder

C14) PJ Verkasalo et al: Risk of cancer in Finnish children living close to
power lines. BMJ 307:895-899, 1993.
  Cohort study of cancer in children in Finland living within 500 m of
high-voltage lines.  Calculated retrospective fields used to define
exposure.  No statistically significant increase in overall cancer
incidence was found.  A significant increase in brain cancer in boys was
due entirely to one exposed boy who developed three brain tumors.  No
significantly increases were found for brain tumors in girls or for
leukemia, lymphomas or "other" tumors in either sex.

C15) JH Olsen et al: Residence near high voltage facilities and risk of
cancer in children. BMJ 307:891-895, 1993.
  Case-control study of childhood cancer in Denmark.  Exposure was assessed
on the basis of calculated fields.  No overall increase in cancer was found
when 2.5 mG (0.25 microT) was used define exposure.  After the data were
analyzed, it was found that if 4 mG (0.40 microT) was used as the cut-off
point, there was a statistically significant increase in overall cancer.
No statistically significant increases in leukemia, lymphoma or brain
cancer were found.

C16) GH Schreiber et al: Cancer mortality and residence near electricity
transmission equipment: A retrospective cohort study. Int J Epidem 22:9-15,
1993.
  Study of people living in an urban area in the Netherlands.  People were
considered exposed in they lived within 100 m of transmission equipment.
Fields in the exposed group were 1-11 mG (0.1-1.1 microT).  An
insignificant decrease in total cancer was found in the exposed group
compared to the general Dutch population.  No leukemia or brain cancer was
seen in the exposed group.

C17) M Feychting & A Ahlbom: Magnetic fields and cancer in children
residing near Swedish high-voltage Power Lines. Am J Epidem 7:467-481,
1993.
  Case-control study of children who lived within 300 m of high-voltage
powerlines.  Exposure assessed by measurements, calculated retrospective
assessments, and distance from lines.  No overall increase in cancer was
found for any measure of exposure.  An increase in leukemia (but not brain
or other cancers) was found in children in one-family homes for fields
calculated to have been 2 mG or above at the time of cancer diagnosis, and
for residence within 50 m of the power line.  No increase in cancer was
found when measured fields were used to estimate exposure.

C18) TL Jones et al: Selection bias from differential residential mobility
as an explanation for associations of wire codes with childhood cancer. J
Clin Epidem 46:545-548; 1993.
  The type of "high current configuration" distribution lines associated
with cancer in the Wertheimer [C1], Savitz [C6] and London [C10] studies
were more common in residential areas that were older, poorer, and which
contained more rental properties.  This could lead to a false association
high current configurations with disease.

D) Epidemiology of Occupational Exposure to Power-Frequency Fields

D1) S Milham: Mortality from leukemia in workers exposed to electrical and
magnetic fields. NEJM 307:249, 1982.
  Proportional mortality study of electrical occupations showing a
significant excess incidence of leukemia.

D2) WE Wright et al: Leukaemia in workers exposed to electrical and
magnetic fields. Lancet 8308 (Vol II):1160-1161, 1982.
  Proportional incidence study of electrical occupations showing a
significant excess of acute, but not chronic leukemia.

D3) S Richardson et al: Occupational risk factors for acute leukaemia: A
case-control study. Int J Epidem 21:1063-1073, 1992.
  Case-control study of acute leukemia across occupations.  An increase in
leukemia was found for all electrical occupations, but the increase was not
statistically significant.  Significant excesses of leukemia were
associated with benzene, exhaust gasses and pesticides.

D4) JD Bowman et al: Electric and Magnetic Field Exposure, Chemical
Exposure, and Leukemia Risk in "Electrical" Occupations, EPRI, Palo Alto,
1992.
  Proportional incidence study of leukemia in electrical versus other
occupations.  For all electrical occupations there was a small, but
statistically significant association of leukemia with electrical
occupations.  There was no relationship between the level of exposure and
leukemia.

D5) T Tynes et al: Incidence of cancer in Norwegian workers potentially
exposed to electromagnetic fields. Am J Epidem 136:81-88, 1992.
  Cohort study of electrical occupations that showed a statistically
significant excess of leukemia but not of brain cancer.

D6) GM Matanoski et al: Leukemia in telephone linemen. Am J Epidem
137:609-619, 1993.
  Case-control of telephone company workers, which showed no statistically
significant increase in leukemia in workers exposed to power-frequency
fields.

D7) B Floderus et al: Occupational exposure to electromagnetic fields in
relation to leukemia and brain tumors: A case-control study in Sweden.
Cancer Causes Control 4:463-476, 1993.
  Case-control study of leukemia and brain tumors of men in all
occupations.  Exposure calculations were based on the job held longest
during the 10-year period prior to diagnosis.  A statistically significant
increase was found for leukemia, but not for brain cancer.

D8) JD Sahl et al: Cohort and nested case-control studies of hematopoietic
cancers and brain cancer among electric utility workers. Epidemiology
4:104-114, 1993.
  Both a cohort and a case-control study of utility workers.  No
significant increase was found for total cancer, leukemia, brain cancer, or
lymphomas.

D9) P Guenel et al: Incidence of cancer in persons with occupational
exposure to electromagnetic fields in Denmark. Br J Indust Med 50:758-764,
1993.
  Case-control study based on all cancer in actively employed Danes. No
significant increases were seen for breast cancer, malignant lymphomas or
brain tumors.  Leukemia was elevated among men in the highest exposure
category; women in similar exposure categories showed no increase in any
type of cancer.

E) Human Studies Related to Power-Frequency Exposure and Cancer

E1) AB Hill: The environment and disease: Association or causation? Proc
Royal Soc Med 58:295-300, 1965.
  Concise statement of the methods use to assess causation in
epidemiological studies.

E2) M Bauchinger et al: Analysis of structural chromosome changes and SCE
after occupational long-term exposure to electric and magnetic fields from
380 kV-systems. Rad Env Biophys 19:235-238, 1981.
  Lymphocytes from occupationally exposed 50 Hz switchyard workers showed
no increase in the frequencies of chromosome aberrations.

E3) K Dickersin et al: Publication bias and randomized controlled trials.
Cont Clin Trials 8:343-353; 1987.
  A general discussion, with examples, of publication bias

E4) I Nordenson et al: Chromosomal effects in lymphocytes of 400
kV-substation workers.  Rad Env Biophys 27:39-47, 1988.
  Lymphocytes from occupationally exposed 50 Hz switchyard workers showed
an increase in the frequency of chromosome aberrations.

E5) DA Savitz & L Feingold: Association of childhood leukemia with
residential traffic density. Scan J Work Environ Health 15:360-363, 1989.
  Analysis of the authors powerline study [C6] using traffic density as the
exposure.  Significant excess risk of leukemia and total cancer associated
with high traffic density.

E6) I Penn: Why do immunosuppressed patients develop cancer? Crit Rev
Oncogen 1:27-52, 1989.
  Review of the relationship between cancer development and immune
suppression

E7) GR Krueger: Abnormal variation of the immune system as related to
cancer. Cancer Growth Prog 4:139-161, 1989.
  Review of the relationship between cancer development and immune
suppression

E8) J.D. Jackson: Are the stray 60-Hz electromagnetic fields associated
with the distribution and use of electric power a significant cause of
cancer? Proc Nat Acad Sci USA 89:3508-3510, 1992.
  Argument that lack of correlation between electric power use and leukemia
rates over time argues against a causal relationship.

F) Biophysics and Dosimetry of Power-Frequency Fields

F1) WT Kaune et al: Residential magnetic and electric fields. BEM
8:315-335, 1987.
  24-hour average measurements correlate poorly with wirecodes.  The
correlation of 0.41, implies that codes account for only 20% of the
variability in average fields.

F2) J Sandweiss: On the cyclotron resonance model of ion transport. BEM
11:203-205, 1990.
  Cyclotron resonance theory inconsistent with basic physical principles
because radius of ion rotation would be about 50 m, and because collisions
would occur much too often for resonance to be achieved.

F3) G Theriault: Cancer risks due to exposure to electromagnetic fields.
Rec. Results Cancer Res. 120:166-180; 1990.
  Good, but dated review. Has good residential and occupational dosimetry
data.

F4) RK Adair: Constraints on biological effects of weak
extremely-low-frequency electromagnetic fields, Phys Rev A 43:1039-1048,
1991.
  ╥Because of the high electrical conductivity of tissues, the coupling of
external electric fields in air to tissues of the body is such that the
effects of the internal fields on cells is smaller than thermal noise╙.  To
get an effect you need a resonance mechanism, and "such resonances are
shown to be incompatible with cell characteristics. . . hence, any
biological effects of weak ELF fields [less than 500 mG, 50 microT] on the
cellular level must be found outside of the scope of conventional physics".
 Also notes that the current induced by walking in the Earth╒s static field
are greater than those induced by a 4 microT (40 mG) 60-Hz field, and that
any resonance found at 60 Hz would not work at 50 Hz.

F5) T Dovan et al: Repeatability of measurements of residential magnetic
fields and wire codes. BEM 14:145-159, 1993.
  Remeasure of homes that had been included in Savitz study [C6] found that
neither measured fields nor wire codes had not changed significantly over a
five-year period.

End: powerlines-cancer-FAQ/part3