EMF Testing Pacemaker Testing regarding RF Radio Frequency Radiation Effects on Pacemakers: An EMF Consulting Case Study
214.912.4691
My employee has a pacemaker – is it safe for him / her / them to return to work around certain EMF and EMI electromagnetic interference sources?
This post about how technical and difficult it can be in the field to make a judgment call about whether an employee with a biomedical implant can get a return to work medical clearance or if they have to be re-assigned. (or in worst case scenarios, find another job) I have “sanitized” the post to protect client confidentiality but the narrative is that one consultant wrote a report which indicated that an employee could NOT return to work because of the equipment that he was using / exposed to.
But my report was more along the lines of a conditional answer that addressed the manufacturer / employer concerns about the potential danger of allowing a worker to continue their position at a steel mill.
It illustrates that there is more to a survey than reading a meter, jotting down numbers and writing a report. You have to weigh more subtle factors and understand certain foundational principles to help your client and support the recommendations that are made.
Pacemakers & Biomedical Implant Electromagnetic Interference EMF / EMI Testing – EMF Surveys
EMF RADIATION TESTING ACTUAL FIELD DISCUSSION
Q. After reviewing the 2 EMI surveys that were conducted at IH4 dating 9/27/22 and 3/27/23, Environmental Health and Safety have a few items that need to be clarified in order to make an informed decision for the employee who has the cardiac implant. Items of concern are below and are directly related to the Motorola radio’s and microphones that the employee would be required to use as part of their daily tasks.
Can you please contact the appropriate persons at the survey companies that were used in order to gain clarification on the above concerns.
* NOTE: The following answers are from Joel-Anthony Gray, the owner and actual surveyor for ScanTech Technical Consulting.
Greetings Client,
My answers are below – thank you!
Q. Were both surveys conducted for the cardiac implant that the employee actually has implanted?
A. I can only speak for the survey I conducted in March 2023 which was specific to the cardiac implant for the employee in the Stripper Bldg & West Guard shack located at 1000 Industrial Road Chicago, IN.
Q. How were the surveys conducted?
A. This question is vague – please be more specific. What I can say at this juncture is that I personally performed the survey onsite on working, energized equipment under field conditions and prepared the relevant report as I have done on a large number and variety of facilities.
Q. Were both surveys conducted on the Motorola XPR 7750e 2 way radio and microphone?
A. I have detailed notes on exactly that model of 2 way radio and the RF levels measured and they were specified in the EMI Guidelines sheet.
Q. Were similar instruments used to take the measurements?
A. From what I can tell in looking at the other report, RF (Radio Frequency) power meters were used in both surveys using the same units in V/m or Volts per Meter, but it is unlikely that the instrumentation was identical in make and model.
Please note that RF readings can be tricky to get with exact accuracy; it is not like measuring temperature or conducted voltage. This is due to the physics behind electromagnetic radiation where effects such as near-field / far field behavior, shadowing, reflections, absorption, attenuation, emissions from nearby devices such as cell phones, constructive and destructive interference can all contribute to the RF measurement on the meter.
However my long experience in working with RF (over 40 years) plus a Bachelor’s in Electrical Engineering (2014) has granted me with sufficient intuition and judgment to evaluate the validity and relevance of what I am seeing on an instrument.
Q. Why does the survey reference level table from 9/27 use the Boston Scientific CRM EMI reference level and the survey from March 2023 use Boston Scientific CRT-D EMI reference level tables?
The term CRM refers to Cardiac Rhythm Management which encompasses an entire family of devices including pacemakers, Internal Cardio-Verter Defibrillators, (ICD) etc.
A CRT-D is specifically a subset of CRM devices and in this case refers to a Cardiac Resynchronization Therapy Defibrillator.
The survey performed by ScanTech was specific to the device for the employee instead of an entire family of devices, but future devices can use the same raw data to make safety determinations.
Q. Why are the results so different? For the survey on 9/27 the safe distance for the employee from the radio is 5 ft. and the microphone at 0 ” is borderline, were as the 3/27 survey states that the safe distance from the radio is the opposite hip of the implant (less than 5 ft.) and the microphone needs to be at least 6″ from the implant.
Excellent question! (not in bold because it is harder to read the more technical information to follow)
I have examined Table 2 on page 6 of the competitor’s consulting report which I note is professionally prepared and in the past I have spoken with Mr. Redacted myself whom I consider to be a friendly competitor as he has asked me for advice before. Having competition is healthy as it makes us sharper, keeps us honest and gives incentive to improve.
Given the frequency ranges of the Motorola XPR 7750e which are in the VHF range (136 – 174 MHz) and the UHF range (403 – 512 MHz) these give wavelengths which range from 1.9 feet to 7.2 feet. This is an important dimension to keep in mind as it determines the Near Field lengths which is calculated by taking the wavelength and multiplying by 0.159. (= 1 / 2 * pi).
This gives Near Field dimensions which range from 3.6″ – 13.2″ or just over a foot and inside of this zone (which is also known as the Reactive / Inductive Near Field) there is a VERY rapid decrease in RF power levels which follow 1 / r^3 out to the Fresnel or Transition Zone where the decrease is less rapid (1/r^2) until you reach the edge of the Far Field (or Fraunhofer distance) where the power decrease becomes more linear.
Looking at the Table 2, the falloff in V/m from 1′ to 5′ is fairly linear which does not entirely fit the falloff I would expect in the Fresnel / Transition zone where it should fall off with the inverse square law.
The measurements I took of the Motorola while it was keyed up (transmitting) gave a value of 285 V/m at point blank range to the radiating antenna. I estimated the IPG (Implantable Pulse Generator which is the heart of any CRM) to be placed under the left clavicle which from the right hip is about 2 feet. There I measured 10 V / m which more closely fits with the mathematical RF model just described and also my experience in the field.
I do not know why the other readings taken at 1 – 5 feet ranged from 99.4 – 110.6 V/m as shown in Table 2 as I was not present. One thing I do agree with is that 100 V/m is the generally accepted safe RF limit for a CRM. (implied by the Exceeds Guidelines and Borderline at 99.1 and 99.4 V/m) I do have a few reservations about the definition of the Near Field being less than one foot away in Footnote 2 on page 6 as the math does not abruptly change from Near Field to Far Field, but has a Transition / Fresnel Zone mentioned previously with a measurable distance which is dependent on antenna length and RF frequency.
What to do?
Here is my experience and judgment:
1) The body of a patient has a significant water content of 60 – 70% (depending on age and hydration) along with tissues and bone. This material greatly reduces RF energy so a radio hanging on the hip has to traverse some amount of this density as well as distance and this further shields the IPG. (Implantable Pulse Generator)
2) I have given this recommendation to dozens of other customers (95% of whom use similar Motorola radios) and I have yet to hear of a complaint or read of an incident where a hip worn radio caused a problem.
3) These EMI specs for pacemakers and other similar biomedical implants are likely conservative as most engineers put in at least a 50% buffer for for safety.
The Microphone
The microphone does not emit any significant RF radiation as implied in the competitor’s report though there is probably a trace of RF from a phenomena known as induction re-radiation. (think of a faint echo) But again, I was not there so I don’t know how far the microphone was held away from the radio unit itself.
My biggest concern with 2 way radios are the microphones because they are often slung over the left shoulder and hang right over the IPG site. This can be a problem because all Motorola microphones have a relatively strong DC magnet that is not significantly impeded by body tissue and can affect a CRM. There is a customer I have who uses magnetic name badges and employees with implants HAVE complained of an altered behavior in their device when wearing these.
Fortunately, the DC magnetic field has a very rapid falloff (generally 1/ r^3) so slinging over the other shoulder (6″+) should avoid any issues.
Hopefully this clears up any concerns about my official recommendations.
Best Regards,
Joel-Anthony Gray CIH, CSP, BSEE, CHMM, CHP (pending) 214.912.4691
ScanTech Technical Consulting – Industrial Health & Safety / Environmental / Biomedical / Electromagnetic “The Unusual Problem Specialists” since 2002
B.S. Electrical Engineering / Specialization Minor in Nanoscience Technology
B.S. Bioengineering & Biomedical Engineering (pending – University of Texas at Dallas)
A.S. Electronic Telecommunications
Certificate in Nanoscience and Nanotechnology (UTD School of Engineering and Computer Science)
Graduate Certificate in Industrial Hygiene (Tulane University School of Public Health and Tropical Medicine )
Certified Industrial Hygienist # 12082 CP ABIH / BGC (American Board of Industrial Hygiene & Board of Global Credentialing)
Certified Safety Professional # CSP-40131 BCSP (Board of Certified Safety Professionals)
Certified Hazardous Materials Manager # 29984 (Institute of Hazardous Materials Management)
Certified Radio & Display Instrumentation Technician (Delco Electronics)
Certified Health Physicist – AAHP (pending)
Certified Non-Ionizing Radiation (NIRAD including RF & EMF) Safety – Colorado State University
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ScanTech Technical Consulting is owned and operated by Joel-Anthony Gray who has over 22 years of experience as an EMF consultant, EMI troubleshooting expert and nuclear radiation testing consultant for a variety of commercial and industrial customers. While there is currently no such thing as a Certified EMF Consultant as far as the United States industrial and scientific community at large is concerned, what ScanTech offers is extensive education, experience and multiple certifications in non-ionizing radiation, industrial safety and hygiene. (listed here EMF Credentials) He holds numerous degrees and certifications which qualify him for this level of expertise. Call 214.912.4691
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