RRVA AMIC Working Cancer Hypothesis

The RRVA Aviator Medical Issues Committee

Introduction.  In late 2019, the Red River Valley Fighter Pilot Association (RRVA) organized its Aviator Medical Issues Committee (AMIC). The AMIC is composed of RRVA members at large that include a group of retired and practicing medical professionals, each with deep aerospace medicine training, knowledge, and experience. The mission of the AMIC is to address health issues of vital interest to RRVA membership and all military aviators. To date, the AMIC is focusing its analytic and advocacy effort on two issues. Of those two issue areas, the one discussed in this statement is our work addressing the incidence and causes of cancers that seem to disproportionately afflict US military aviators.

Background.  RRVA members know of numerous squadron mates and flying partners diagnosed with cancer at a rate that seemed to exceed average cancer incidence rates in the US general population.[1] Consequently, in Fall 2019 RRVA conducted an informal survey of its 3,400+ members.[2] The AMIC processed 894 survey responses for a return rate of 26% (2019 membership level). Of the 894 responses, 500 (56%) disclosed respondent personal cancer incidence; 13% of this group indicated multiple personal cancer diagnoses. The majority of respondents (RRVA members only) knew one or more fellow military aviators stricken with cancer. The survey’s most frequently reported cancer was melanoma; second was prostate cancer. The 2019 RRVA pilot cancer survey was not a classic scientific study that utilized rigorous design norms and methodologies.

In May 2021, the US Air Force School of Aerospace Medicine (USAFSAM) at Wright-Patterson AFB, OH, reported findings of its Air Force aviator retrospective cohort study.[3] This study assessed Air Force fighter aviators relative to other Air Force officers and the U.S. general population with multiple control groups. The study cohort included 34,976 active duty fighter aviators who served from 1 June 1970 to 31 December 2004 contrasted to a control group of 386,190 Air Force officers that served 1970-2004.[4] The USAFSAM study indicated prostate cancer had a significantly higher incidence among fighter aviators than both of the study’s control groups.[5] Other cancers with higher occurrence among fighter aviators included melanoma. These two USAFAM study outcomes corroborated RRVA’s 2019 Pilot Cancer Survey findings. Other cancers identified by the USAFSAM May 2021 study with higher incidence/mortality rates among Air Force aviators rates were thyroid, testicular, and non-Hodgkin lymphoma. The study is praiseworthy for its synoptic discussion of potential military operating causal factor attribution including cohort study biases.

Other Studies.  The RRVA AMIC is grateful to the Air Force for its willingness to conduct its first-ever cohort study regarding cancer incidence and mortality. Of note, the Defense Health Agency of the Department of Defense is conducting the U.S. military’s first-ever multi-service aviator and aviation support personnel study.[6] The DHA is under Congressional mandate to report the findings of this study in 2022.[7]

Discussion. The RRVA AMIC’s working hypothesis of cancers in U.S. military aviators is: that a likely complicated, not entirely understood, nor fully researched chronic occupational exposures to ionizing radiation (IoR) and non-ionizing radiation (NIoR) coalesce with factors potentially unique to military operating environments to elevate cancer incidence/mortality among U.S. military aviators. The operationalization of this hypothesis may account for elevated aviator cancer incidence/mortality documented by a recent U.S. Air Force aviator cancer study.[8]

Within that hypothesis are other notions about how Airmen, Sailor, and Marine aviators operate their aircraft that plays a central role in significantly higher rates of cancer incidence/mortality than non-flying military members and the U.S. general population. For example, present commercial aviation IoR exposures  focus on the operating altitude envelopes of airline aircraft. In contrast, military aircraft may operate in that same altitude band, but in the case of high-performance fighter aircraft, operate up to and beyond 50,000 feet. As depicted in Figure 1., IoR is principally composed of four distinct types of particles with a range of penetration/absorption properties that may impact human health.

U.S. military aviators likely exceed by significant margins what are considered safe annual aerial IoR exposure.[9] IoR exposure levels are proven to increase as altitude increases, with IoR exposure doses at 50,000+ feet several times higher than flight at/near sea level. While Air Force, Navy, and Marine Corps aviators may experience numerous other toxic exposures, RRVA’s working hypothesis focuses on the extensive IoR literature and the absence of a similar body of NIoR exposure scientific and medical scholarship. There is extensive human health and safety IoR literature. In contrast there is a paucity of NIoR exposure research. Here, the U.S. atomic weapon attacks of World War II cast a long shadow over atomic science and radiation medicine.[10] The long established Life Span Study (LSS) documents and researches at scale the multi-generational health effects of Japanese civilians exposed to acute and chronic radiation effects in those attacks.[11]

To return to the AMIC working hypothesis, there is another important aspect of IoR that IoR and so far only IoR has the properties sufficient to cause chemical changes at the cellular level to provoke the formation of cancer cells in humans. The literature extensively documents the cellular activities and interactions of human tissues with decaying radioactive particles that pass through those tissues.[12] Figure 2 is a simplified depiction of the complex direct and indirect impacts of radioactive particles as they decay and interact with cellular DNA. At the cellular level, this is the origin story of IoR established by the literature that demonstrates how IoR exposure can and does cause cancer.

Zooming out to another element of the working hypothesis, the RRVA AMIC takes no position on the diversity of literature that describes low dose/low dose rate state of art medical and scientific thought.[13] However, the AMIC notes a lack of broad scientific/medical consensus on the implications of lifelong chronic low dose/low dose rate IoR exposure.[14] The reasons for this lack of consensus are varied. However, it is noteworthy that in the literature, researchers frequently opine that improved understanding of low dose/low dose rate exposures requires larger study populations.[15] The population size of military aviators stretching back 40+ years not only makes for study cohorts with a helpfully large “n” (study population) but that n is the also the exposure cohort whose health effects need to be better understood to ascertain cancer cause/effect linkages in U.S. military aviators.[16]

Next, foreign regulators used studies and implemented measures to minimize foreign airline aircrew exposures today.[17] Foreign regulators hold that foreign aircrews receive annual IoR dosages that put them into the category of personnel occupationally exposed to ionizing radiation.[18] Interestingly, U.S. military aviators routinely operate at altitudes and block hour levels that exceed those documented in previous studies and by foreign regulation.[19] Some of these studies are mentioned in the USAFSAM May 2021 study. This points to another concern, that of IoR dosimetry. For example, select aerial IoR exposure data can be found in FAA Advisory Circular 120-61B.[20] Additionally, the FAA’s web-based Civil Aviation Research Institute (CARI) 7/7A exposure planning tool offers a more robust aircrew exposure planning baseline. Elsewhere in the world, airline companies are required to track crew exposure.[21] No such exposure tracking occurs among U.S. military aviators who face the same environmental hazards.[22] Meanwhile, many U.S. military aviator aircrews accumulate at least the same, perhaps more IoR exposure as foreign airline crews. Neither the CARI model or FAA data should be construed as authoritative predictions of aircrew cancer incidence and/or mortality. In the U.S., radiation exposure mitigation across the federal government is regulated by the Environmental Protection Agency.[23] The FAA and the U.S. military do not track aviator annual IoR exposure nor do they impose annual exposure limitations.[24]

Pivoting toward NIoR, the other component of the AMIC’s working hypothesis, Figure 3 illustrates the energy spectrum that depicts the relationship of NIoR to IoR. Unlike the substantial body of medical and scientific knowledge associated with IoR, NIoR research is limited and lacks rigor.  

The AMIC’s working hypothesis contains another premise: under-studied NIoR may constitute undocumented radiation exposure. If validated by research, NIoR energy levels may be another causal path for DNA damage at the cellular that elevates cancer risk in aviators with chronic NIoR exposure. The most common sources of concentrated NIoR energy in the military operating environments are termed high-power emitters (HPEs). HPEs are ubiquitous in military operating environments since the mid-1960s.  Within the AMIC’s working hypothesis, aircraft RADARs and aircraft onboard jamming equipment constitute the bulk of the hypothesized NIoR exposure path.[25] Data which measures exposure levels from the HPE equipment that is common throughout military operating environments does not exist. Measurement and study of HPE radiation output effects as discussed here on cellular function and DNA will be new research. Until that research is conducted, absence of NIoR HPE exposure and dosage effects evidence should not be construed as evidence of absence of potential NIoR harm. 

Referring to Figure 3 and another premise of the AMIC’s NIoR working hypothesis is the region of the energy spectrum where ultraviolet light is located.[26] While science documents the effects of ultraviolet light exposure on the ground on humans, there likely is an incomplete understanding of measured effect data as to the ultraviolet protection properties of most military aircraft windshields; specifically, those with large bubble-type canopies common to U.S. fighter aircraft.[27] The statistically higher occurrence of melanoma in the RRVA Pilot Cancer Survey and USAFSAM May 21 aviator cancer study may be linked to these unmeasured effects and their partially understood effects on Airmen, Sailors, and Marines that operate under those aircraft canopies. Some researchers assert melanoma cancer outcomes are actually driven by lifestyle and not aviation factors. Research does not yet rule in/out lifestyle among aviation exposure.[28]

Beyond IoR and NIoR, there could be numerous other causes for higher cancer incidence/mortality among military aviators in the varied military operating environments.[29] The RRVA AMIC takes no position on the weighting of any confounding factors in specific studies, but we do acknowledge the role and presence of these factors among military aviators. In a larger sense, confounding factor variation does not prefigure for analytic disregard; rather, it begs for numerous vertical cause/effect studies. Consequently, the burden of proof for lack of toxic health effect or demonstration of health and safety does not lie with military aviators.

Legislative Priorities.  The USAFSAM May 2021 study is the first study at scale among military aviators and other control groups that may provide certain Veterans stricken with prostate cancer, melanoma, non-Hodgkin lymphoma as a means to obtain Veterans Administration service connection awarded for their cancer. The crux is that cancer seldom manifests during military service or in the year that follows separation and/or retirement. Absent any tool such as the USAFSAM May 2021 study, Veteran military aviators are at significant disadvantage in proving up on the claim for disability and compensation. Meanwhile, military aviators who suffer with cancers other than prostate, melanoma, and non-Hodgkin lymphoma which they perceive is connected to military service, are left to confront numerous and perhaps insurmountable case development challenges in constructing a fully developed case that successfully yields service connection.

The U.S. Air Force, DOD’s largest and most diverse aviation service studied aviator cancers and determined that yes, Air Force aviators suffer cancers at rates of incidence and mortality higher than their non-rated service peers and the U.S. general population. On this basis alone, DOD should direct the Defense Health Agency to undertake numerous aviator cancer nexus studies. However, if as empowered by Section 750 of the FY21 NDAA Secretary of Defense Austin does not direct the conduct of nexus studies, RRVA will advocate for legislation that requires DOD to conduct nexus studies in military aviators. Military aviator cancer nexus studies should examine sources of known and/or unknown carcinogens that are unique to, or found exclusively in military operating environments.

Elsewhere, rather than a narrow strategy that seeks to assist each Veteran aviator with his/her direct service connection, RRVA is proposing a broader strategy that yields a presumptive class.[30] This presumptive class, a proposed Military Aviators Cancers presumptive class would be Congressionally enacted for a group of cancers identified by DOD as caused by exposure to carcinogens in the military operating environment.

Conclusion.  Nexus research of carcinogens in military operating environments will not discourage aviators from military flying. Rather, research will reinforce existing notions of care for the aviator forces of the Air Force, Navy, and Marine Corps. Importantly, data-driven approaches will enable Veterans to obtain the health monitoring, ongoing care, and connection that are products of their service and which they need to assist them in early cancer diagnosis and treatments to improve outcomes. RRVA is committed to those results. RRVA asks Congress, Department of Defense, and Veteran’s Administration to equally commit to delivery of military aviator cancer care and where appropriate, VA claim service connection.

Questions concerning this article, efforts of the RRVA AMIC, or assistance filing a VA claim for a cancer with military aviator service connection, email medical@river-rats.org or email the RRVA AMIC Director at vince.alcazar@river-rats.org.