Ask A Scientist© Environmental Science Archive

Author:     jconner
Text:       I would like to know how to measure the EMF emitted by the various 
appliances around the house. I also live near big power lines and I have read 
of a possible link to the childhood leukemia. Do you have any real information 
(not TV's scare stories). I won a Fluke multimeter and I was ho hoping to use 
it (somehow ) to measure the EMF around my house.

Response #: 1 o f 1
Author:     Eric Dallman
Text:       For starters I would like to congratulate you on realizing that TV 
scare stories and real life are not always the same. Next, I would like to 
briefly address part of your question. Your question is partially a physics 
question with regard to EMF in general. I am assuming here that you are 
referring to electromagnetic fields (rather than electromotive force). 
Electromagnetic fields (EM fields) really consist of two field types, 
electrical (normally measured in volts/meter) and magnetic fields (measured in 
amperes/meter). As far as exposure to EM fields goes, that question falls 
under the discipline of Industrial Hygiene. For many years Industrial 
Hygienists have studied the effects of EM fields on occupationally exposed 
workers. Unfortunately, to get good epidemiological data, many years is often 
not long enough. Many occupational health organizations have established 
limits of exposure to EM fields in the work place. Some, such as the American 
Conference of Governmental Industrial Hygienists (ACGIH) and the Department of 
Energy's proposed guidelines on exposure to non-ionizing radiation were quite 
thoroughly researched. No matter how much research went into the exposure 
limits, a few things remain fundamentally true: exposure levels are set mainly 
to avoid electrical shock hazards, minimize burn hazards, and reduce 
interference with ferrous implants and pacemakers. Exposure levels take into 
account many things including the body's ability to act as an antenna and 
resonate at certain frequencies. Obviously these levels of exposure are much 
higher than those encountered in the typical home. It is very important to 
realize, however, that these are occupational exposure limits. These are 
limits at which it is believed the average worker may be exposed day after 
day, forty hours per week for an entire working career without suffering 
adverse health effects. These limits are not intended to be used for constant 
exposures such as one might get in their home. Recently, several reports were 
published showing a link between long term exposure to low frequency EM fields 
(such as produced by a 60 Hz power line) and leukemia. These studies were 
based mainly on seemingly higher incidence of leukemia in children living near
power lines. Though perhaps the children did have a higher incidence of 
leukemia, the studies failed to take several important things into 
consideration. The children in the studies typically lived in run down 
neighborhoods and were probably exposed to a host of things more likely to 
cause leukemia than low level, low frequency EM fields. The studies did not 
really show a cause-effect relationship between EM fields and leukemia, they 
established a correlation between higher leukemia rates and impoverished 
children. Subsequent studies (taking more factors into account) have shown 
that the leukemia rate was not linked to EM fields. I cannot recall any study 
that is shown more than perhaps a small correlation between leukemia and low 
level EM fields. Other studies have linked exposure to EM fields produced by 
computer screens (CRTs) to a number of problems including still births, low 
birth weight, etc. Most of these studies did not take into account the posture 
and lifestyles of the exposed women. Follow-up studies (taking more factors 
into account) have shown either no or a very low correlation between CRTs and 
still birth, etc. Needless to say, some of these studies have shown some 
correlation (though low) between long term, low level EM field exposure and 
adverse health effects. In most cases it has been difficult to establish an 
actual cause-effect relationship. However, until proven otherwise, I would 
recommend minimizing needless exposure to EM fields (though I still 
occasionally use an electric blanket). I realize I have discussed many studies 
and have not provided a single reference. I have quite a few articles and 
reports on this subject at work, and access to quite a few more. Give me a few 
days to dig them out and I will provide you with some references and 
additional sources of information. With regard to using a multimeter to 
measure EM fields around the home, the answer is no way. Multimeters measure 
currents and voltages through wires, not field strengths in air. There are 
instruments available to measure electrical and magnetic field strengths. The 
model we purchased last year at work (relatively inexpensive as these things 
go) ran about $5,000. Obviously they are not within financial reach of the 
average home owner. I will try and find you some data on average EM field 
strengths in homes near power lines and their relative risk factors based on 
current studies. A point I may not have made clear in is that the occupational 
exposure levels for EM fields are primarily for wavelengths in the radio 
frequency and microwave range. Also, the CRT that I referred to is usually 
called a VDT (video display terminal). Here are some additional sources of 
information: The American Conference of Governmental Industrial Hygienists has 
three publications that would be of interest to you. They are Pub. # 9120, 
Biological Effects of (Transmission) Line Fields; Pub. # 9214, Extremely Low 
Frequency Electromagnetic Fields: The Question of Cancer; and (least 
applicable) Pub. # 9185, Biological Effects and Medical Applications of 
Electromagnetic Energy. These publications range from about $50 - $100 so you 
may want to check a technical library. For more info on these items, ACGIH is 
located in Cincinnati. Their phone # is (513) 661-7881. There is an article in 
VDT NEWS (9#2:1, 1992) that discusses some research done in Finland on EMF 
intensity. This study recommends VDTs produce no more than 4 mG (milligauss). 
Another VDT NEWS (9#4:7,'92) reports on induction of magnetic fields in 
computer furniture. MICROWAVE NEWS (11#3:2,'91) contains a grizzly report of 
rampant cancer in three California and one Pennsylvania site located near high 
tension power lines (though no cause effect relationship is established, it 
makes interesting evening news). I would put more faith in the 3 ACGIH 
publications than the others. Here is another reference "Safety and Health" 
Magazine (National Safety Council), February. 1993: Electric Current: A New 
Scare for the '90s. A rather vague article, but possibly more "findable" than 
some of the others I referenced. Also, Microwave News can be contacted at 
Microwave News, P.O. Box 1799, Grand Central Station, NY, NY 10163. The Safety 
and Health article gives a brief overview of research to date and several tips 
to reduce EMF exposure (though their conclusions are as vague as mine were as 
a result of limited research in this field).