new electronic devices and equipment lead to increased convenience in our lives . however , there is concern about possible hazards of the electromagnetic fields that these devices and equipment produce and their effects on human health .
electromagnetic fields have the properties of both electric and magnetic fields ( mfs ) , which have considerably different properties and possibly different ways of influencing the human body . electric fields are easily shielded or weakened by conducting objects , even human skin , but mfs are not so easily blocked .
therefore , most recent studies have focused on the health effects of mfs because mfs are not readily shielded and are easier to measure than electric fields . in 1979 ,
wertheimer and leeper first reported that increased development of childhood cancer was associated with proximity of the home to electrical power lines .
since then , many groups have studied the biological effects of mfs . among the spectrum of mfs ,
the extremely low - frequency ( elf ) mfs range from 3 to 3000  hz and include the 50- and 60-hz frequencies used in power lines and electric appliances , classified as possibly carcinogenic to humans ( group 2b ) by the international agency for research on cancer .
the international commission on non - ionizing radiation protection ( icnirp ) issued guidelines for limiting exposure to electromagnetic fields in 2010 , and these guidelines for the general public restricted mf exposure to 2  g at 60  hz for any length of time to limit current density to prevent effects on nervous system function .
however , many epidemiologic studies have suggested a more stringent 2  mg as the highest acceptable level for long - term exposure .
the guidelines by swedish board for technical accreditation for computer monitors also restrict computer monitors to produce elf - mf of no more than 2  mg at 30  cm .
furthermore , savitz et al suggested an association between arrhythmia - related cardiovascular disease and elf - mfs , which is consistent with the previous study by sastre et al in addition to heart diseases , elf - mfs are also associated with breast cancer .
several studies have reported that elf - mfs increase the risk of breast cancer . moreover , more than 20 studies of the effects of elf - mfs on cognitive dysfunction and dementia , including a recent 2014 study , reported a positive association between elf - mf exposure and cognitive dysfunction . despite increasing attention to the elf - mf and its association with diseases ,
many electrical apparatuses are used and becoming essential for treatment and diagnosis of diseases in hospitals , but not much attention has been given to the potential risk from the elf - mfs produced .
lee et al and roh et al reported how much anesthesiologists are exposed to elf - mfs during surgery by , respectively , spot measurements and repetitive measurements , similar to the present study .
riminesi et al measured elf - mfs from infant warming systems and incubators in neonatal intensive care units and reported high elf - mfs above 2  mg .
hanada measured mfs higher than the icnirp exposure guidelines in some hospital areas . with the technological advances of the late 20th century ,
the concept of surgery through a scope , that is , laparoscopic surgery and minimally invasive surgery , became a reality .
currently , the advantages of laparoscopic surgery and minimally invasive surgery , including shorter hospital stays , decreased postoperative pain , and a rapid return to preoperative activity , are well accepted . despite the benefits of laparoscopic surgery , there are drawbacks .
the da vinci surgical system ( intuitive surgical , mountain view , ca ) has emerged as an alternative tool to overcome the disadvantages of conventional laparoscopic surgery , such as 2-dimensional visualization and limited degrees of motion and freedom . in addition ,
robotic surgery systems eliminate physiologic tremors and the fulcrum effect and provide excellent ergonomics and improved dexterity .
computerized enhanced robotic surgery using the da vinci surgical system has been used successfully in cardiac surgery , urology , general surgery , orthopedics , maxillofacial surgery , ophthalmology , neurosurgery , gynecology , and even in surgical gynecologic oncology . with its increasing practical uses and significant potential promise ,
many studies have been published regarding costs and benefits of robotic versus conventional laparoscopic surgery in several centers with surgical robotic systems .
most surgeons are already exposed to elf - mfs from monitors , computers , and medical apparatuses that are placed in limited spaces
. moreover , laparoscopic and robotic surgeries , which provide benefits in terms of surgical outcome , require more devices than other surgeries and hence produce more elf - mfs , increasing the exposure hazard to hospital staff in operating rooms , especially to surgeons .
surprisingly , there are no reports regarding how much elf - mf surgeons are exposed to during laparoscopic and robotic surgeries . because surgeons may be in operating rooms for a long time every day , the exposure time is also considerably long , which increases the potential hazards of elf - mfs to surgeons .
to our knowledge , this is the first study to measure elf - mfs at the position of the surgeon 's heart during laparoscopic and robotic surgeries using a robotic surgical system .
our objectives were to compare the elf - mfs during laparoscopic and robotic surgery and to identify the source of elf - mfs in the operating room .
exposure levels of surgeons to elf - mfs in 20 laparoscopic surgeries and 20 robotic surgeries at the yonsei university health system in seoul , korea , were measured from july to october in 2014 . for robotic surgeries ,
the da vinci surgical system was used . to represent the whole robotic surgery and at the same time to fairly compare laparoscopic and robotic surgery , 2 types of surgery from the colorectal and hepato - biliary - pancreatic surgery divisions
each surgery from both divisions uses almost the same equipment in laparoscopic and robotic surgery , except the robot system is used only in the robotic surgeries .
low anterior resection was chosen in the colorectal surgery division , and cholecystectomy was chosen in the hepato - biliary - pancreatic surgery division .
all subjects were informed of the purpose and procedure of the experiments and provided written consent before joining the study .
the yonsei university health system institutional review board approved the study protocol ( project no . 4 - 2014 - 0398 ) . to measure elf - mf exposure levels of the surgeons , an emdex lite ( enertech consultants , campbell , ca ) , a portable device to periodically measure elf - mf intensity ,
was fitted in position over each surgeon 's heart during each surgery ( figure 1a ) .
the emdex lite can measure elf - mfs between 40 and 1000  hz ranging from 0.1 to 700.0  mg with a resolution of 0.1  mg and accuracy of 2% .
the elf - mf intensity was sampled and stored inside the device every 4 seconds from the start to finish of each surgery .
the data were then retrieved by connecting the measuring device to a personal computer and analyzed by emcalc 2000 ( enertech consultants ) analysis and graphical software .
( a ) the emdex lite was fitted over each surgeon 's heart during surgery .
( b ) the surgeon at the master console of the da vinci surgical system .
( d ) the operating table and surgeon during laparoscopic surgery . the mean and standard deviation of elf - mf intensity during each surgery were calculated .
the proportions of exposure levels 2  mg in each surgery were also calculated . the mann 
whitney u test was used to compare the mean exposures to elf - mfs of the surgeons . the u value calculated by mann 
whitney u test for each group is the difference between the possible minimum rank that the group can take [ n(n  +  1)/2 ] and the sum of the ranks in the group , where n is the group sample size .
the smaller the u value is , the less likely it has occurred by chance .
the null hypothesis was that the mean exposures to elf - mfs of surgeons were the same in laparoscopic and robotic surgeries .
we did not accept the null hypothesis for a u value 127 ( the critical value for total surgeries ) and a u value 23 ( the critical value for surgeries for each division ) , each corresponding to p  <  0.05 .
all reported p values were 2-sided , and p values < 0.05 were considered statistically significant .
all statistical analyses were performed using the statistical package for the social sciences software ( version 20 , ibm spss statistics ; ibm corp , armonk , ny ) .
exposure levels of surgeons to elf - mfs in 20 laparoscopic surgeries and 20 robotic surgeries at the yonsei university health system in seoul , korea , were measured from july to october in 2014 . for robotic surgeries ,
the da vinci surgical system was used . to represent the whole robotic surgery and at the same time to fairly compare laparoscopic and robotic surgery , 2 types of surgery from the colorectal and hepato - biliary - pancreatic surgery divisions
each surgery from both divisions uses almost the same equipment in laparoscopic and robotic surgery , except the robot system is used only in the robotic surgeries .
low anterior resection was chosen in the colorectal surgery division , and cholecystectomy was chosen in the hepato - biliary - pancreatic surgery division .
all subjects were informed of the purpose and procedure of the experiments and provided written consent before joining the study .
the yonsei university health system institutional review board approved the study protocol ( project no . 4 - 2014 - 0398 ) .
to measure elf - mf exposure levels of the surgeons , an emdex lite ( enertech consultants , campbell , ca ) , a portable device to periodically measure elf - mf intensity , was fitted in position over each surgeon 's heart during each surgery ( figure 1a ) .
the emdex lite can measure elf - mfs between 40 and 1000  hz ranging from 0.1 to 700.0  mg with a resolution of 0.1  mg and accuracy of 2% .
the elf - mf intensity was sampled and stored inside the device every 4 seconds from the start to finish of each surgery .
the data were then retrieved by connecting the measuring device to a personal computer and analyzed by emcalc 2000 ( enertech consultants ) analysis and graphical software .
( a ) the emdex lite was fitted over each surgeon 's heart during surgery .
( b ) the surgeon at the master console of the da vinci surgical system .
the mean and standard deviation of elf - mf intensity during each surgery were calculated .
the proportions of exposure levels 2  mg in each surgery were also calculated . the mann 
whitney u test was used to compare the mean exposures to elf - mfs of the surgeons . the u value calculated by mann 
whitney u test for each group is the difference between the possible minimum rank that the group can take [ n(n  +  1)/2 ] and the sum of the ranks in the group , where n is the group sample size .
the smaller the u value is , the less likely it has occurred by chance .
the null hypothesis was that the mean exposures to elf - mfs of surgeons were the same in laparoscopic and robotic surgeries .
we did not accept the null hypothesis for a u value 127 ( the critical value for total surgeries ) and a u value 23 ( the critical value for surgeries for each division ) , each corresponding to p  <  0.05 . all reported p values were 2-sided , and p values < 0.05 were considered statistically significant .
all statistical analyses were performed using the statistical package for the social sciences software ( version 20 , ibm spss statistics ; ibm corp , armonk , ny ) .
tables 1 and 2 present the data including exposure levels of elf - mfs in the laparoscopic and robotic surgeries , respectively .
table 3 shows comparisons of the mean elf - mf exposures of surgeons in the laparoscopic and robotic surgeries . in the 20 laparoscopic and 20 robotic surgeries ,
the mean elf - mf exposure was 0.6    0.1  mg for the laparoscopic surgeries and 0.3    0.0  mg for the robotic surgeries ( significantly lower with mann 
=  0 , p  <  0.001 ) . in 8 laparoscopic surgeries and 1 robotic surgery ,
in addition , the proportions of exposure levels 1  mg and < 2  mg were 2.4% for laparoscopic and 0.1% for robotic surgeries .
the proportions of exposure levels < 1  mg were 97.5% for laparoscopic and 99.9% for robotic surgeries .
exposure levels of surgeons to extremely low - frequency magnetic fields during laparoscopic surgeries exposure levels of surgeons to extremely low - frequency magnetic fields during robotic surgeries comparisons of the mean extremely low - frequency magnetic field exposures of surgeons during the laparoscopic and robotic surgeries in the colorectal surgery division , the mean elf - mf exposures during the 10 laparoscopic surgeries ( ranging 2.96.3  hours in duration ) and the 10 robotic surgeries ( ranging 1.93.4  hours in duration ) were 0.6    0.1 and 0.3    0.0  mg , respectively ( significantly different with mann  whitney u 
0.001 ) ( table 3 ) . in the hepato - biliary - pancreatic surgery division ,
the mean elf - mf exposures during the 10 laparoscopic surgeries ( ranging 1.12.0  hours in duration ) and the 10 robotic surgeries ( ranging 0.71.3  hours in duration ) were 0.7    0.1 and 0.3    0.0  mg , respectively ( significantly different with mann  whitney u 
considerable attention has been focused on the association of elf - mfs with human diseases , especially on their potential hazards regarding cancer in children , heart diseases , breast cancer , and cognitive dysfunction .
the guidelines for the wide spectrum of frequency have been established for short - term exposure by the icnirp and the world health organization .
the most stringent elf - mf level for weak long - term exposure suggested by many epidemiological studies is 2  mg . in one study ,
the mean elf - mf exposure of anesthesiologists during surgery in a standing position was 5.8    5.2  mg with 70% of them exposed to levels of 2  mg .
another study done by ubeda et al reported spot measurements ranging from a minimum of 0.3    0.1  mg in nurses to a maximum of 3.9    1.3  mg in physiotherapists , with exposure levels of surgeons , physicians , and radiologists included in this range .
our group has also assessed the daily exposure of endodontic personnel to elf - mfs ; the mean elf - mf exposure of 10 personnel in an endodontic section during working hours was 0.3    0.4  mg . in our study ,
the total mean exposures to elf - mfs were 0.6    0.1  mg ( n  =  20 ) for laparoscopic surgeries and 0.3    0.0  mg ( n  =  20 ) for robotic surgeries .
the proportions of exposure levels 2  mg were 0.11% for laparoscopic surgeries and 0.01% for robotic surgeries .
laparoscopic and robotic surgeries showed elf - mfs comparably lower than 2  mg , which was considered a safe limit in many studies .
moreover , the mean mf exposures of the surgeons in the laparoscopic and robotic surgeries were lower than the mean mf exposure level of 1.1  mg in homes in north america .
therefore , it can be considered safe for patients who spend a considerably short time in the operating room . however , because surgeons and hospital staff spend considerably more time in operating rooms , it would be prudent for them to avoid elf - mf exposure elsewhere .
the elf - mf exposures during robotic surgeries were significantly lower than those during laparoscopic surgeries ( p  <  0.001 ) , because of the distance of the master console from the operating table .
we reported in previous studies that the mean elf - mf exposures of anesthesiologists were 5.8    5.2  mg with 70% of them exposed to levels of 2  mg .
we can infer from this study that a large portion of the elf - mfs originate from the surgical operating table , which is close not only to the surgical equipment but also to the anesthesia and monitoring equipment .
the levels of exposure to elf - mfs from robotic surgeries showed a consistent value of 0.3  mg regardless of the different surgery divisions because the position of the measuring device to the master console is consistent for each robot system .
moreover , the mean distance between the master console of the robot system and the operating table was 440    55  cm . at a distance of 90 to 120  cm from an electric appliance ,
the mf is at background level ; therefore , 440  cm is enough distance so that the mf is at background level at the master console .
in addition , the master console monitor uses lcd screens , which produce a very weak mf due to the low current and power .
therefore , the surgeon 's head during robotic surgery could be exposed to only a weak mf .
the elf - mfs from the operating table and nearby equipment did not reach the master console where the surgeon sat , and we found that elf - mfs from the master console of the robot system were 0.3  mg at the position of the surgeon 's heart ( figure 1c and d ) . in figure 1b , the operator is sitting close to the master console with his head close to the monitor .
although 0.3  mg is considered a low elf - mf exposure level , the surgeon sits at the monitor for a fairly long period of time , and not much is known about the cumulative effect of low - intensity elf - mfs .
we measured elf - mfs over the surgeon 's heart because previous studies reported harmful effects of elf - mfs on the heart .
although the effects of elf - mfs on other diseases such as breast cancer and diseases associated with the brain are also well known , it was most convenient for surgeons to attach the measuring devices over the heart , where it was also least likely to interfere with the surgeon 's ability to operate . until now , it has not been clearly understood what level of weak and long - term elf - mf is harmful to humans .
many studies have been conducted not only in animals but also in human cells to determine the toxic effects of elf - mfs , the function of electrons in dna , and their association with the response to mfs . however
, more research is needed to clarify the exact pathogenesis of how weak long - term elf - mfs affect human health , not only at the dna level but also directly at the cell level . with the advancement of technology , many devices have been developed for diagnosis and treatment of diseases .
they have become essential tools for physicians , and as a result , hospitals now have a high density of technologically advanced instruments .
these instruments produce elf - mfs that could be harmful to surgeons and medical staff who regularly spend long periods of time in the operating room .
although laparoscopic and robotic surgeries that require more electronic devices than other surgeries would produce more elf - mfs , there have been no previous studies regarding elf - mfs in these types of surgery . to our knowledge , this is the first study to provide basic reference data of elf - mfs in robotic surgery compared with conventional laparoscopic surgery . in conclusion ,
the exposure of surgeons to elf - mfs in robotic surgery was significantly lower than that in laparoscopic surgery because of the distance of the master console from the operating table .
although the elf - mf level of laparoscopic surgery was still considerably lower than 2  mg , which is the most stringent level considered safe in many studies , we should not overlook the effects of long - term exposure of elf - mfs during many surgeries over the course of a surgeon 's career .
second , we do not know the exact sources of elf - mfs during laparoscopic and robotic surgeries , but this study focuses on the elf - mf exposure of surgeons , not on the individual devices and equipment that produce the elf - mfs . future studies on the sources of elf - mfs in the operating room might be promising .
manufacturers , physicians , and associated administrators should not overlook elf - mf exposure and its long - term effects on humans , even though the mf intensity is weak .
 abstractthe development of new medical electronic devices and equipment has increased the use of electrical apparatuses in surgery . 
 many studies have reported the association of long - term exposure to extremely low - frequency magnetic fields ( elf - mfs ) with diseases or cancer . 
 robotic surgery has emerged as an alternative tool to overcome the disadvantages of conventional laparoscopic surgery . 
 however , there has been no report regarding how much elf - mf surgeons are exposed to during laparoscopic and robotic surgeries . in this observational study 
 , we aimed to measure and compare the elf - mfs that surgeons are exposed to during laparoscopic and robotic surgery.the intensities of the elf - mfs surgeons are exposed to were measured every 4 seconds for 20 cases of laparoscopic surgery and 20 cases of robotic surgery using portable elf - mf measuring devices with logging capability.the mean elf - mf exposures were 0.6    0.1  mg for laparoscopic surgeries and 0.3    0.0  mg for robotic surgeries ( significantly lower with p  <  0.001 by mann  
 whitney u test).our results show that the elf - mf exposure levels of surgeons in both robotic and conventional laparoscopic surgery were lower than 2  mg , which is the most stringent level considered safe in many studies . 
 however , we should not overlook the effects of long - term elf - mf exposure during many surgeries in the course of a surgeon 's career . 
INTRODUCTION
METHODS
Subjects
Measurement of ELF-MFs
Statistical Analyses
RESULTS
DISCUSSION