Unveiling the spectrum: Understanding directed energy weapon injuries and military health care implications

Abstract

Introduction:

Directed energy weapons (DEWs) are emerging technologies that are transforming the modern battlespace. Despite their increasing presence, the associated injury patterns and health outcomes remain poorly understood. This review aims to consolidate existing knowledge on DEW-related injuries to assist military medical professionals in improving clinical care.

Methods:

A scoping review was conducted in accordance with PRISMA-ScR guidelines and included peer-reviewed and grey literature from 1980 to Nov. 30, 2024. Databases searched included PubMed, MEDLINE, AccessMedicine (textbooks), the Cochrane Library, EMBASE, Google Scholar, and Military Legal Resources (U.S. Army JAG School). Studies that focused on chemical, acoustic, and electrical/electromagnetic weapons were excluded because of differing pathophysiology. Two independent reviewers performed screening and data extraction. Results were synthesized narratively.

Results:

Out of 200 identified studies, 33 met inclusion criteria. Most documented injuries involved thermal damage to skin, internal organs, and eyes. Notably, data were sparse on reproductive effects and the management of DEW injuries in polytrauma. Evidence suggests that DEWs may inflict central nervous system or deep tissue damage without external signs, potentially delaying diagnosis and treatment. Injury severity varied by energy type, anatomical target, and exposure duration.

Discussion:

DEWs introduce novel clinical challenges for military health care providers, with injury profiles that may not align with traditional trauma paradigms. Standard physical assessments may fail to detect certain injuries. Long-term health outcomes following DEW exposure are largely unknown. There is an urgent need to develop and validate clinical guidelines and treatment protocols as DEWs become increasingly integrated into military operations.

Lay Summary

Directed energy weapons (DEWs), such as high-energy lasers and microwaves are increasingly used in modern warfare, but their health impacts are not well understood. This review explores the limited available research to understand how DEWs can injure the human body. Most known effects involve burns, eye damage, and internal injuries without visible signs. Unlike traditional weapons, DEWs may cause delayed symptoms or damage organs without leaving a mark on the skin. This study also highlights how little clinical guidance exists for treating these injuries, especially in combat settings. Medical personnel may need new diagnostic and treatment approaches to manage such cases. The article emphasizes the need for better awareness, protective equipment, and research to keep pace with the growing use of DEWs on the battlefield.

Introduction

Weapon modernization, development, and adaptability are cornerstones of an armed force’s ability to maintain military superiority in an ever-changing and fluid combat environment. Arms races have shaped political landscapes and have influenced policy such that a nation’s military capability is often considered directly proportional to their resources and weapon efficacy.¹ Among the latest of these technological developments are directed energy weapons (DEWs).

In the military context, directed energy (DE) is defined as the ability to project focused electromagnetic energy in a manner sufficient to produce a defensive or offensive effect at militarily relevant distances within the battlespace.² DEWs can engage targets with near instantaneous effects across vast distances, with the added advantage of firing at numerous targets without depleting ammunition.³ High-energy laser (HEL) and other high-power electromagnetic weapons allow versatility; some are used to degrade electronics within computer-guided armament systems, whereas others physically destroy airborne targets.² Currently known military uses include counter-air defence, target identification, tracking, counter-intelligence, search and reconnaissance, and electronic warfare.² As of 2020, at least nine of the 10 largest military powers worldwide had publicly announced laser-based weapons programs, with particular focus on counter-unmanned aerial system operations.²

There are three main types of DEWs, each occupying a different region of the electromagnetic spectrum. Wavelength and intensity are the principal factors that determine a weapon’s capability. HELs produce singular and narrow beams of light and are typically situated in the infrared-to-visible region of the electromagnetic spectrum.³ Variations of this type of weapon comprise both pulsed and continuous beams and are generally employed against one target at a time. HELs can generate more than one kilowatt of power, making them 200,000 times more powerful than typical laser pointers and capable of melting steel.³ Millimetre wave weapons yield similar power outputs to HELs, but they generate larger beams and are therefore capable of engaging multiple targets simultaneously. Finally, high-power microwave weapons produce microwaves, which have longer wavelengths than both HELs and millimetre wave weapons. High-power microwave weapons can generate more than 100 megawatts of power, and they can also engage numerous targets because of their larger beams.³ Many clinicians are familiar with the ionizing energy of X-rays and gamma rays that are capable of breaking molecular bonds and damaging DNA; DEWs emit non-ionizing energy and injure primarily through thermal excitation and cellular interactions.⁴ We have included all of the above energy types in this review and collectively refer to them as DEWs. It is important to highlight that the exact effects of the energy on human organ systems will depend on the type, power, intensity, and duration of exposure to any one of these weapons.

In late 2016 and early 2017, U.S. diplomats serving in Cuba reported neurological symptoms, thought to be associated with exposure to directional auditory and sensory phenomena of unknown origin.⁵ A retrospective case series by Swanson et al.⁵ describes persistent cognitive, vestibular, and oculomotor symptoms, sleep disturbance, and headaches. While the source of exposure remains unclear, the reported symptoms were consistent with a traumatic brain injury, without an associated traumatic mechanism. A specific discussion of Havana syndrome is beyond the scope of this paper, but the events in Havana spurred discussion about the potential use of DEWs as (neuro)weapons and the importance of developing a medical defence strategy against such threats. Recognition of the cause of injury is critical to proper medical management of such cases, including protection from further exposure/injury and acute treatment of symptoms.⁶

The varied nature of military operations (land, sea, air) also varies the potential threats from DEWs. Certain injuries may become more common to certain theatres of operation, and knowledge of this fact may aid the military medical professional in anticipating injuries. For example, ground personnel may be more likely to encounter close-contact exposure,² but terrain may affect line-of-site capabilities and render some DEWs ineffectual. In contrast, aircrew flying at altitude and battleships in the open water are excellent targets for line-of-site DEWs, particularly since DEWs are capable of functioning at vast distances.³ Ocular trauma is also more historically likely in these line-of-site environments.²

Military medicine must adapt to the evolving threat of DEWs. Medical researchers, practitioners, engineers, and policy makers will need to collaborate to establish a comprehensive research framework from policy to the point of injury. As DEW use on the battlefield continues to expand, understanding injury profiles will be crucial for developing preventative measures, diagnostic methods, and treatment protocols. In light of the paucity of currently available medical literature, this scoping review aims to summarize what is known, characterize potential injuries, suggest a potential approach to assessments and treatments, and inspire further discussion and research in this field.

Methods

The authors followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) extension for Scoping Review to inform the search and selection of articles for review, as illustrated in Figure 1.

Figure 1.

PRISMA flow diagram, modified from systematic review diagrams to describe our scoping review methodology

Identification

Two primary authors conducted the literature search using specific criteria developed with the assistance of a Canadian National Defence Headquarters (NDHQ) librarian. Search parameters included peer-reviewed or grey literature articles in English from 1980 to Nov. 30, 2024. The databases included were PubMED, MEDLINE, AccessMedicine (textbooks), Cochrane Library, EMBASE, Google Scholar, and Military Legal Resources (U.S. Army JAG School). The initial search terms were “directed energy weapon,” “laser weapon*,” and “high energy weapon*”; however, these were yielding a multitude of articles for ballistic, chemical, and acoustic weapons that were not relevant. In collaboration with the NDHQ librarian, we further defined the search to include the following weapons terms: “directed energy weapon*,” “directed-energy weapon*,” “laser weapon*,” “high energy laser*,” “high power microwave* weapon*,” “high power electromagnetic*,” “millimeter wave weapon*,” “active denial system” (when searched with some of the above terms), “particle beam weapon*,” “charged particle beam weapon*,” and “radiated energy weapon*.” These weapon terms were further combined with health terms, including “health,” “injury,” “trauma,” “traumatic brain injury*,” “burn,” “death,” “casualty,” “eyesight,” and “hearing.” These health terms were chosen to include both broad terms (to be as inclusive as possible) and those curated from our subject matter knowledge. Note that the asterisk (*) is used to widen the search to include all words that start with the same letter combination.

The following exclusions were made to focus the review on the potential effects of weapons-grade DEWs on human tissue:

• Other forms of DEWs including chemical, acoustic, and electrical (TASER) are excluded, as the energy transferred from these weapons is in the form of chemical reaction, longitudinal pressure waves, and electrical current; this scoping review focuses on injuries resulting from exposure to directed, non-ionizing, electromagnetic radiation.

• Articles specifically referencing “Havana syndrome” were excluded given ongoing uncertainty about the causative exposure and clinical effects.

• Articles on ionizing radiation were excluded (e.g., gamma rays, X-rays, and particles).

• Articles addressing chronic, low-level exposure to electromagnetic fields were excluded (e.g., from natural sources, power lines, electrical devices).

• Articles with no discussion of injuries or health effects were also excluded.

Furthermore, there were military terms added for the Google Scholar search to help target the results further. These included combinations of the following terms in addition to the search terms above: “war,” “military,” “army,” “navy,” and “armed forces.”

Screening

Articles were initially screened for relevance by two independent primary authors. Title screening was conducted first, followed by abstract screening. If the title included key words and appeared relevant to the study question, the abstract was read to ensure it matched the defined inclusion criteria. After independent review, the primary authors compared results, and any disputes were settled by consensus or a third author.

Eligibility

The same two primary authors independently reviewed the full articles identified through the abstract screening. If articles met the exclusion criteria, they were eliminated. Any disputes were settled through consensus or a third author. During review, articles were further categorized by energy system, affected body parts, and study context. The energy systems were divided as HEL, microwave, or radiofrequency (RF). Body systems include eyes, skin, internal organs (including the central nervous system), fertility and reproductive organs, cell function, and general health effects. The authors also separated articles by the area of focus: military/defence, scientific research, or industrial applications. Finally, article summaries were developed to enable thematic analysis that informed our results and discussion.

Results

Of the 200 articles identified, 33 were selected for review (Table 1). The types of DEWs included HELs (n = 20; 61%), microwave (n = 15; 45%), and RF (n = 13; 39%). The breakdown of these findings is summarized in Table 2. Most articles reported on ocular injuries (n = 14; 42%), internal organs (n = 8; 24%), and skin (n = 8; 24%). Out of the 33 articles in total, 11 articles (33%) were peer-reviewed and original scientific research studying the direct effects of energy on tissue, 11 (33%) were literature reviews, and eight (24%) were unclassified background documents written to inform defence policy, legal treatises, or advocacy documents. While all articles were selected to elucidate the potential health effects of DEWs, military use of DE was the focus of 18 articles (55%), while the others examined DE use within industrial settings (n = 7; 21%) or within a laboratory/research setting (n = 12; 36%).

Table 1.

Primary energy types and body systems

Reference	Energy type	Body system
Barkana Y, Belkin M. Laser eye injuries. Surv Ophthalmol. 2000;44(6):459-78. doi:https://doi.org/10.1016/s0039-6257(00)00112-0	Laser	Eyes
Beinart R, Nazarian S. Effects of external electrical and magnetic fields on pacemakers and defibrillators. Circ. 2013;128(25):2799-809. doi:https://doi.org/10.1161/CIRCULATIONAHA.113.005697	Radiofrequency	Internal organs
Cain CP, Polhamus GD, Roach WP, et al. Porcine skin visible lesion thresholds for near-infrared lasers including modeling at two pulse durations and spot sizes. J Biomed Opt. 2006;11(4):041109. doi:https://doi.org/10.1117/1.2338815	Laser	Skin
Candidate 7018 (University of Oslo, Faculty of Law). Laser and Directed Energy Weapons within International Humanitarian Law	Laser radiofrequency microwave	Eyes
Commiskey PW, Heisel CJ, Paulus YM. Non-therapeutic laser retinal injury. Int J Ophthalmic Res. 2019;5(1):321-35. doi:https://doi.org/10.17554/j.issn.2409-5680.2019.05.90	Laser	Eyes
Congressional Research Service. Navy shipboard lasers: background and issues for congress. Washington, DC: Library of Congress; 2021 Apr 28. Report No.: R44175. Available from: https://crsreports.congress.gov/product/pdf/R/R44175	Laser radiofrequency microwave	Non-specific
DeLisi MP, Schmidt MS, Hoffman AF, Peterson AM. Thermal damage thresholds for multiple-pulse porcine skin laser exposures at 1070 nm. J Biomed Opt. 2019;25(3). doi:https://doi.org/10.1117/1.JBO.25.3.035001	Laser	Skin
Dong G, Zhou H, Gao Y, et al. Effects of 1.5-GHz high-power microwave exposure on the reproductive systems of male mice. Electromagn Biol Med. 2021;40(2):311-20. doi:https://doi.org/10.1080/15368378.2021.1891091	Microwave	Fertility / reproductive organs
Foster KR, Garrett DC, Ziskin MC. Can the microwave auditory effect be weaponized? Front Public Health. 2021;9:788613. doi:https://doi.org/10.3389/fpubh.2021.788613	Microwave	Central nervous system
Foster KR, Laakso I, Chalfin S. Nonuniform exposure to the cornea from millimeter waves. Health Phys. 2021;120(5):525-31. doi:https://doi.org/10.1097/HP.0000000000001376	Radiofrequency	Eyes
Gibot L, Kolosnjaj-Tabi J, Bellard E, et al. Evaluations of acute and sub-acute biological effects of narrowband and moderate-band high power electromagnetic waves on cellular spheroids. Sci Rep. 2019;9. doi:https://doi.org/10.1038/s41598-019-51686-9	Radiofrequency microwave	Cell function
Gillow JT. Another weapon too far: the anti-personnel laser. J R Soc Med. 1995;88(6):347-9.	Laser	Eyes
Gooch JM, Harvey RR, Parham-Bruce W, Rogers BZ, McLin LN. United States Air Force School of Aerospace Medicine laser injury guidebook. Air Force Research Laboratory; 2012.	Laser	Eyes
Habauzit D, Nugue G, Bourbon F, et al. Evaluation of the effect of chronic 94 GHz exposure on gene expression in the skin of hairless rats in vivo. Radiat Res. 2020;193(4):351-8. doi:https://doi.org/10.1667/RR15470.1	Microwave	Skin
Harris MD, Lincoln AE, Amoroso PJ, et al. Laser eye injuries in military occupations. Aviat Space Environ Med. 2003;74(9):947-52.	Laser	Eyes
Hudson SJ. Eye injuries from laser exposure: a review. Aviat Space Environ Med. 1998;69(5):519-24.	Laser	Eyes
Lazov L, Padarev NI. Laser safety in army education. Land Forces Acad Rev. 2023;28(1). doi:https://doi.org/10.2478/raft-2023-0009	Laser	Eyes, skin
Lyu CY, Zhan RJ. Accurate analysis of limiting human dose of non-lethal laser weapons. Def Technol. 2021. doi:https://doi.org/10.1016/j.dt.2021.03.018	Laser	Skin
Marshall J. Blinding laser weapons. BMJ. 1997;315:1392. doi:https://doi.org/10.1136/bmj.315.7120.1392	Laser	Eyes
Merritt JH, Kiel JL, Hurt WD. Considerations for human exposure standards for fast-rise-time high-peak-power electromagnetic pulses. Aviat Space Environ Med. 1995;66(6):586-9.	Radiofrequency microwave	Cellular function
Office of the U.S. Air Force’s Chief Scientist for Directed Energy. Directed energy futures 2060: visions for the next 40 years of directed energy. Kirtland Air Force Base (NM): Air Force Research Laboratory; 2021. Available from: https://www.afrl.af.mil/Portals/90/Documents/RD/Directed_Energy_Futures_2060_Final29June21_with_clearance_number.pdf	Laser radiofrequency microwave	Non-specific
Seet B, Wong TY. Military laser weapons: current controversies. Ophthalmic Epidemiol. 2001;8(4):215-26. doi:https://doi.org/10.1076/opep.8.4.215.1610	Laser	Eyes
Stuck BE, Friedl KE. The US Army Medical Department’s role and accomplishments in laser development and use. In: Biomedical implications of military laser exposure. Washington, DC: Borden Press, Government Printing Office; 2020.	Laser	Eyes
Tulsawani R, Sharma P, Sethy NK, et al. Acute exposure of 532 nm laser differentially regulates skin tissue transcription factors. PLoS One. 2020;15(3). doi:https://doi.org/10.1371/journal.pone.0230175	Laser	Skin
U.S. Government Accountability Office. Science & tech spotlight: directed energy weapons. GAO-23-106717. May 2023.	Laser radiofrequency microwave	Non-specific
Vecchia P, Matthes R, Ziegelberger G, et al. Exposure to high frequency electromagnetic fields, biological effects and health consequences (100 kHz-300 GHz). International Commission on Non-Ionizing Radiation Protection; 2009. ISBN: 978-3-934994-10-2	Radiofrequency microwave	Central nervous system, internal organs, cellular function, fertility/reproductive organs
Washington MA, Dinh DT, Ibarra CA, Kua SC. A brief primer on the concept of the neuroweapon for U.S. military medical personnel. J Spec Oper Med. 2023;23(4):70-4. doi:https://doi.org/10.55460/SX1S-ZO4J	Radiofrequency microwave	Central nervous system
Wright BA, Powell E, Dodson WW. Directed energy: medical effects of radio frequency exposure (microwave & millimeter wave) — a literature review. Air Force Research Laboratory; 2013. AFRL-SA-WP-SR-2013-0004.	Radiofrequency microwave	Skin, central nervous system, internal organs
Yao C, Dong J, Ren K, et al. Accumulative effects of multifrequency microwave exposure with 1.5 GHz and 2.8 GHz on the structures and functions of the immune system. Int J Environ Res Public Health. 2023;20:4988. doi:https://doi.org/10.3390/ijerph20064988	Microwave	Internal organs
Ziskin MC, Alekseev SI, Foster KR, et al. Tissue models for RF exposure evaluation at frequencies above 6 GHz. Bioelectromagnetics. 2018;39(1):173-89. doi:https://doi.org/10.1002/bem.22110	Radiofrequency	Skin
Franchini V, Regalbuto S, De Amicis A, et al. Genotoxic effects in human fibroblasts exposed to microwave radiation. Health Phys. 2018;115(1):126-39. doi:https://doi.org/10.1097/HP.0000000000000871	Microwave	Cellular function, fertility/reproductive organs
Svec L, Beer J, Freeman D. Directed energy in the military environment. Naval Surface Warfare Center; 2012.	Laser	Eyes
NATO Research and Technology Organisation. The human effects of non-lethal technologies. RTO-HFM-073; 2006.	Laser radiofrequency microwave	Cellular function, eyes

Notes: Articles identified with this search strategy, as well as the primary energy type(s) and body system(s) they describe.

Table 2:

Number of articles identified per study type, energy type, body system, and study context

	Number of articles
Study type
Literature review	11
Industry guideline	1
Case report/case series	2
Original research	11
Policy/advocacy	8
Energy type
High-energy laser	20
Microwave	15
Radiofrequency	13
Body system
Eyes	14
Skin	8
Internal organs (including the central nervous system)	8
Fertility/reproductive organs	3
Cell function	5
Non-specific health effects	3
Context
Industrial	7
Military	18
Science	12

Note: Several articles discussed multiple energy types and body systems within more than one context; the total number of articles under each heading therefore does not equal the total number of articles included in this review.

Discussion

While there has been a significant amount of research into the health effects of chronic, environmental exposure to non-ionizing radiation, there appears to be less known about potential injuries related to weapons-grade DE exposure. As these weapons systems further permeate theatres of war, the military medical community will need to refine its approach to injuries. Currently, only ocular and skin/thermal injuries are well understood, and no research was found looking at the potential role DEWs may play in a complex, multi-system trauma patient — the type likely to be found on a modern battlefield.

Skin/thermal injury

DEWs damage skin tissue primarily through thermal excitation, and the depth of injury is affected by the DEW frequency/wavelength. For example, millimetre waves affect the outer layer of skin, and tissue damage is largely superficial; frequencies between 30 and 300 GHz penetrate less than 1 mm.⁷ Lower frequency, longer wavelength energy (e.g., microwaves) penetrate deeper. Factors that affect absorption and transport of thermal energy within skin tissues include water content, skin thickness, and blood flow.⁷ Metal objects near, on, or within a person can reflect and/or concentrate the energy field, leading to significant burn trauma.⁸

At a skin temperature between 38°, humans will generally report a warming sensation.⁸ The rate of temperature change, the skin temperature before exposure to the thermal stimulus, the location of the stimulus, and the environmental temperature may all affect the sensation of warmth or pain with heating.⁸ Significant pain may be experienced when the skin temperature rises to 45° to 55°, but damage to skin tissues is not expected unless the exposure is prolonged.⁸ Thresholds for thermal burns are 55° to 60° for a superficial (first-degree) burn, 60° to 65° for a superficial partial-thickness or deep partial-thickness (second-degree) burn, and over 70° for a full-thickness (third-degree) burn.⁸

Although the literature suggests that there is no difference in burn thresholds between males and females,⁸ it does support different thermal pain thresholds, with females experiencing heat pain more intensely and unpleasantly.⁹ These findings highlight sex-based differences in thermoception and pain perception, and these variations in sensory processing and pain responses could contribute to differences in injury outcomes and recovery patterns between males and females.

Narrowly focused studies on the effects of DE on skin tissue were conducted by DeLisi et al.,¹⁰ Lyu and Zhan,¹¹ Tulsawani et al.,¹² and Habauzit et al.¹³ DeLisi looked specifically at the threshold for thermal damage to the skin of Yucatan mini-pigs when exposed to a pulsed 1,070-nm laser, demonstrating that tissue damage is affected by the total duration of pulse sequence.¹⁰ The recent study by Lyu and Zhan examined the effects of non-lethal laser weapons on human skin and concluded that thermal injury thresholds for 1,064-nm lasers depend on spot size, with doses between 8.17 and 8.93 J/cm² effectively causing intense pain without irreversible damage.¹¹ Habauzit et al. and Tulsawani et al. examined gene expression in rat skin exposed to 94 GHz and 532 nm, respectively. Habauzit et al. determined that chronic, long-term exposure at 94 GHz did not significantly modify gene expression in their test subjects,¹³ while Tulsawani et al. reported that the pattern of gene expression at 532 nm was affected by radiance (power per unit area) and noted repression of genes related to wound healing at higher radiance levels.¹²

Central nervous system (CNS) and internal injury

Novel to DEW injuries is the potential for deep tissue damage without visible external injury. Similar to the way that ionizing radiation therapy in cancer treatments targets deep tumours without extensive skin injury, DEWs at certain wavelengths are able to penetrate the body and heat internal organs and structures without necessarily elevating skin temperature or showing any superficial signs of injury. Symptoms of DEW injury to deep tissues would likely vary depending on the organ system(s) affected, and they may be non-specific (e.g., anxiety, fatigue, headache, nausea, and vomiting). It is also possible that organ damage may not be detectable until hours or days after the DEW exposure.⁸

At internal temperatures above 42° to 43°, proteins within the CNS begin to denature and cell damage occurs, resulting in deterioration of CNS function.⁸ These effects impede thermoregulatory responses such as vasodilation and sweating. Thermal injury to the CNS by DEWs is likely to present clinically with heat stroke signs and symptoms (headache, disorientation, seizure, altered level of consciousness), but it may exclude the environmental exposures that would usually precipitate this presentation. Experiments exposing mice to pulses of high-power microwave energy have demonstrated an increase in brain temperature, resulting in seizure and loss of consciousness.⁸

The effect of DEWs on internal organs and overall core temperature would be influenced by the duration of the exposure, the focality of the exposure, and the ambient temperature and relative humidity.⁸ Medications such as anticholinergic drugs may accentuate a person’s response to DEW exposure by suppressing some thermoregulatory responses, such as sweating and vasodilation, and other medications or comorbid medical conditions may affect a person’s susceptibility to DEWs through reduced cardiovascular reserve, reduced CNS activity, and volume status.⁸

In addition to thermal CNS injury, exposure to DEWs may disrupt neurophysiological processes. These processes are poorly understood, but pulsed, low-intensity RF and microwave radiation may produce symptoms such as headache, fatigue, dizziness, irritability, anxiety, forgetfulness, impaired concentration, and internal sound perception.⁴ A literature review conducted by Vecchia et al.¹⁴ suggests that the double blind studies included in their review were unable to demonstrate causality between RF exposure and these subjective symptoms.

Exposure to electromagnetic gradients can induce currents in conductive tissue; this exposure may activate peripheral nerves, resulting in myoclonus or fasciculations.⁴ These effects would be expected to cease with discontinuation of the electromagnetic/DEW exposure. The literature also recognizes a “microwave auditory effect,” or the “Frey effect,” which can occur when pulsed microwave energy is absorbed; the very small but rapid increase in temperature results in an acoustic pressure wave that is detected as sound.¹⁴ Interestingly, the conversion of electromagnetic waves to thermoacoustic waves initially supported the hypothesis that the neurological symptoms experienced by diplomats in Havana in 2016 were caused by a novel DEW.

Beinart¹⁵ explains that in addition to direct effects on internal organs, DEWs have the potential to affect medical devices such as internal pacemakers or defibrillators. Radiofrequency fields can lead to inductive heating of conductive materials, resulting in tissue heating and burns.

Eyes

Ocular injury is currently the best-understood mechanism of injury in DEW environments because of the relatively large amount of data from accidental and industrial exposures to lasers. We see these data incorporated into occupational health and safety plans (e.g., Lazov and Padarev,¹⁶ United States Air Force School of Aerospace Medicine,¹⁷ Gillow,¹⁸ and International Committee of the Red Cross¹⁹). The risk of blindness from laser exposure is well established; in 1995, the United Nations developed a protocol on blinding laser weapons, calling for a ban on the use of laser weapons that are designed to target vision and cause permanent blindness.¹⁹ The UN protocol requires signatories to take precautions to avoid incidental permanent blindness when using laser systems, but it does not prohibit the use of laser systems for non-blinding military purposes.

Laser eye injuries, either intentional or accidental, can be anticipated in any theatre where DEWs or associated technologies are being used. Ocular anatomy and the focusing power of the eye make the retina particularly sensitive to DEWs. Ocular structures (i.e., the cornea and lens) focus light in the near-IR and visible spectrums to a retinal image about 5 to 30 mm in diameter, increasing the irradiance at the retina over 10,000-fold compared to the irradiance experienced at the cornea.²⁰ Magnifying optical devices used on the battlefield (e.g., binoculars) can further increase the ocular radiation exposure.

The nature and severity of injury caused by laser irradiation depends on wavelength, power density, duration of exposure, and tissue affected.²¹ Retinal injury can range from sub-clinical to full-thickness macular holes; foveal injury is more likely to result in loss of visual acuity than peripheral injury.²⁰ Less angular spreading is seen with green light than red light, resulting in greater risk of injury from green lasers.²² Large pupils allow for increased transmission of photon energy, and increased retinal and choroidal pigmentation allow for broader absorption of the energy.²¹

While the mechanisms of injury and risk factors for severe injury are complex, certain symptoms are suggestive of laser-induced ocular injury. These symptoms may include reduced visual acuity, visual field defect, paracentral scotoma, photophobia, metamorphopsia, and chromatopsia.²⁰ Other symptoms, such as chronic ocular, facial, or head pain, and ocular redness and irritation, may not be associated with laser injury.²¹ In their review of laser eye injury case reports and case series, Commiskey et al.²² note that reports of accidental laser eye injuries outnumber confirmed cases of retinal injury, with a more challenging diagnosis for less severe injuries.

Cellular function

Cellular electromagnetic fields, regulated by the ion pumps and ion channels that maintain the membrane potential of cells, play an important role in cell homeostasis, stem cell differentiation, and embryo development.²² The electromagnetic fields generated by DEWs have the potential to interfere with endogenous electromagnetic fields, thus affecting cell function. This remains an active area of research on both the electromagnetic interactions within and between cells, and the effects of exogenous electromagnetic fields on these interactions.

Gibot et al.²³ exposed tumour cell spheroids and normal human dermal fibroblast spheroids to high-powered electromagnetic signals and noted no significant cellular level effects. Habauzit et al.¹³ assessed the effect of 94 GHz on gene expression of skin in rats and concluded that chronic, long-term exposure did not significantly modify gene expression in young or adult rats. Yao et al.²⁴ observed the thymus, spleen, and mesenteric lymph node of rats exposed to multifrequency microwave doses and noted injury to the structures and functions of the immune system, as well as a reduction in the number of immune cells, cytokines, and immunoglobulins in peripheral blood. Tulsawani et al.¹² found that acute exposure to a 532-nm laser affected gene expression of rat skin tissue and that these effects depended on radiance exposure parameters.

Fertility and pregnancy

With the increased prevalence of radiofrequency and microwave devices, concerns around the health effects (including fertility and reproduction) of electromagnetic fields (EMF) has increased. The International Commission on Non-Ionizing Radiation Protection’s review of the biological effects and health consequences of high frequency EMF suggests that RF may adversely affect both male fertility and pregnancy outcomes, if exposure levels are sufficient to increase core temperature.¹⁴ However, it is difficult to extrapolate the potential effects of EMF to DEWs, as field effects may be significantly different from those of weapons-grade directed energy. We uncovered only a single study that was specifically related to directed energy and fertility; Dong et al.²⁵ looked at the effects of whole-body exposure to 1.5 GHz high-powered microwaves on mouse testes and spermatozoa and reported no obvious damage to the male mouse reproductive system.

Little is known about the potential effects of DEWs on female reproduction, particularly the effects of HELs. It is likely that injuries incurred from DEW exposure (including increased core temperature and direct injury/burns to reproductive organs, or a developing fetus) could have significant effects on fertility or pregnancy.

Combined trauma

We did not uncover any current evidence on the role of DEW in complex multi-system trauma, likely because these weapons systems are still novel and injuries are likely under-reported. DEWs are just one of many tools available on the modern battlefield, and they may not be used in isolation. Individuals simultaneously exposed to DEWs and conventional weaponry may present complicated, multi-system injuries. The most immediately detectable injuries are likely to be those sustained from conventional weaponry, and the most obvious cause for injury will be heralded by the noise, flash, and smoke of conventional munitions. The most devastating injuries, however, may be internal and invisible, and caused by a quiet and distant DEW. Recognition of DEW use on the battlefield will be key to appropriately treating this combined trauma. Details such as DEW frequency/wavelength, intensity, and exposure time may be difficult to ascertain, but they are important when assessing, prioritizing, and treating the combination of trauma and DEW injuries.

Health care implications

It is crucial to understand the potential injury profiles of DEW exposure to guide the development of injury prevention and mitigation measures. Based on what is currently known, injury type and severity are influenced by the time on target, intensity of exposure, and wavelength/frequency of the DEW. Time on target may be minimized with personal or geographic dosimeter-type devices designed to recognize exposure and alert the user. Personal protective equipment should be designed to shield against both superficial burns and internal injuries. Particular attention also needs to be paid to eye protection given the susceptibility of ocular structures to laser injuries.

If injuries are sustained, health care professionals, including pre-hospital and emergency room providers, will need to assess for visible injuries, internal injuries, and the potential for late-presenting or long-term sequelae of injuries. DEW characteristics, including power or exposure, may not be known by clinicians, further complicating patient assessment. The approach to assessing DEW injuries may need to combine established trauma or burn protocols with heat injury protocols or organ-specific protocols. Providers will need to maintain a high degree of suspicion for multi-system injuries and may need to access multiple diagnostic testing modalities.

Conclusion

Advancements in weapons technology have given rise to DEWs, including HELs and RF devices, capable of both non-lethal and lethal force. There is very little publicly available literature about the health effects of DEWs, and what is available often describes accidental exposure to industrial or occupational laser, microwave, or RF devices rather than weapons-grade systems. While potential health effects may be extrapolated from the existing literature, DEW injury patterns may be complex and unpredictable. It will be important to develop equipment and procedures for exposure recognition and injury prevention. Existing treatment guidelines may be usefully combined when patients present with injuries related to DEW exposure or combined DEW and conventional weapon injury. Assessment, diagnostic, and treatment protocols will need to be refined when DEWs are actively introduced into the modern battlefield and as our understanding of injury patterns evolves.

Limitations

A significant limitation of this scoping review was the inclusion of the search term “weapon.” The focus of this paper was to explore what is known of weapons-grade DEWs, but this focus resulted in the exclusion of raw industrial/accidental injury data. Many of the referenced literature reviews and policy background documents included in this paper did include industry data, but it is possible that a broader search may have turned up information not included in this review. We were also only able to review publicly available data on these weapons systems. It is plausible that militaries currently using or developing DEWs understand the injury potential of these weapons systems, but this information is classified and not publicly accessible. Further, it should be noted that some of the research indicates feasibility of injury rather than definitive proof of adverse outcomes. This scoping review was also limited to the English language, and no specific nations were included or excluded from the search strategy. Our goal is to provide a holistic picture of possible injury mechanisms based on current research. As further retrospective studies arise and injuries occur, there will inevitably be a refinement of the injuries referenced in this article.

Biographies

Jacinta McNairn, MD, MSc, BEng, is a medical officer and flight surgeon at the Canadian Forces Health Services (Atlantic) in Halifax, Nova Scotia, Canada. She also practices rural emergency medicine at multiple Nova Scotia hospitals. Prior to her career in medicine, McNairn worked as a consulting engineer and helicopter pilot.

Farriss Blaskovits, MD, CCFP, MSc, is a military physician and dive medical officer at the Canadian Forces Health Service (Atlantic) in Halifax, Nova Scotia, Canada. Prior to medicine, she trained as a nurse and completed a master’s in neuroscience in Ontario, Canada.

Makyla St. Onge, BBA, RMC, is a Royal Canadian Air Force helicopter pilot currently working for the Directorate of Flight Safety (DFS) as an accident investigator. Prior to DFS, she obtained a bachelor’s degree in business administration from the Royal Military College of Canada and flew the CH-146 Griffon helicopter with 430 Tactical Helicopter Squadron.

Jillian Coleby, MD, CCFP(EM), is an assistant professor at Dalhousie University and an emergency physician in Halifax, Nova Scotia, Canada. She holds a fellowship in pre-hospital and transport medicine and serves as Medical Officer (Emergency Medicine) with 1 Canadian Field Hospital. Her scholarly work focuses on mass gathering, pre-hospital, and military medicine.

Aasim Khan, BSc, is a combat medic at 12 (Vancouver) Field Ambulance. He completed his undergraduate degree in biomedical physiology at Simon Fraser University, where he was involved in cardiac physiology research. He also works as a paramedic with BC Emergency Health Services.

Paul Dhillon, CCFP(EM), is a family physician with added certification in emergency medicine and holds qualifications in dive medicine, as a flight surgeon, and in submarine medicine. He is a medical officer at 11/12 (Vancouver) Field Ambulance in Vancouver, British Columbia, Canada, and currently serves as Brigade Surgeon for 39 Canadian Brigade Group.

Funding Statement

No funding was received for this article.