By Esther Nahon, Opinions Editor
As an out-of-towner at Stern College for Women, I have found myself booking and boarding flights to and from my hometown in Miami much more frequently than the typical college student. What used to be a fun and exciting adventure looking out the airplane window has since turned into a dreadful three hours filled with germ exposure, turbulence, ear pains and ending with a cranky, disoriented post-flight passenger. Given my physical discomforts from just a three hour flight, I wondered how the pilots, flight attendants, and crew-members manage to spend endless hours on transatlantic flights. Forget about the average person’s fear of being 30,000 feet high in the sky; how do these pilots maintain their sanity and health when they are trapped in a machine with no clean or fresh air, exposed to a multitude of people, germs, chemicals and toxins on a daily basis?
Ongoing research as well as several studies have been conducted to analyze the adverse health effects that arise in those professionally involved in aviation. Among the primary factors contributing to DNA damage and cancer development in this population is exposure to cosmic radiation. Cosmic radiation, also known as ionizing radiation, are very excited, highly-charged particles such as x-rays and gamma rays that have the potential to disrupt the body’s cellular structure and/or cause genetic damage upon exposure. Though humans are exposed to this form of radiation at all times, the Earth’s atmosphere does a good job at shielding us from its potentially harmful effects while at sea level. However, once escalating in altitudes that resemble those of commercial air-line flights, the exposure rates to cosmic radiation are one hundred times greater than usual. The prolonged exposure to this type of radiation at low doses serves as the basis and leading risk factor for many of the genotoxic studies done on pilots and aircraft personnel.
In a risk assessment study, blood samples were drawn from 48 male crew-members working long-haul flights as well as from a control group of 48 healthy males from the airline’s ground staff. Researchers performed cytogenetic testing as well as the micronucleus test and fluorescent in-situ hybridization (FISH) on their cells. These tests look for cell mutations and chromosomal abnormalities that could be indicative of genotoxic exposure. FISH proved to be the most effective testing method as it detected significantly higher levels of translocations, breaks, and gaps in the flight-crew members’ chromosomes in comparison to the control group of crew members. Translocations and chromosomal breaks are forms of chromosomal damage that could be indicative of genetic disease. Pilots with more years of flight experience displayed a larger frequency of translocated chromosomes, suggesting the increased genetic risk with longer exposure to cosmic radiation. The studies suggested the need for preventative measures to be taken to protect aircraft personnel since a potential correlation between chromosomal translocations and cancer exists. Though not to a statistically significant degree, these researchers also detected the presence of micronuclei, ring, and dicentric chromosomes among the flight crew members, all of which further exemplify chromosomal damage.
In a similar study, researchers set out to analyze the chromosomal aberrations present in the peripheral blood lymphocytes of civil pilots and flight-crew members as a distinct result of ionizing radiation exposure. An elevated presence of dicentric (chromosomes composed of two centromeres) and ring chromosomes (chromosomes that underwent deletion of its telomeres forming a “ring” shape) were found in flight personnel in comparison to the control group, demonstrating a statistically significant amount of damage in their DNA. These same aberrations were detected and attributed to cosmic radiation in an earlier study in which researchers tested the lymphocytes of pilots and stewardesses through sister chromatid exchange (SCE).
In addition to the increased ring and dicentric chromosomes, they also found an unexpected presence of symmetrical translocations (exchange of chromosomal material between non-homologous chromosomes) and trisomies (presence of an extra chromosome) in the test group’s data which further demonstrates the genotoxic danger of their profession. Though this process of SCE does not directly classify agents as mutagenic, SCE levels have been found to increase following DNA damage due to known carcinogens, thus making it a valuable biomarker in detecting genotoxicity in cells.
Aside from the exposure to cosmic radiation from the outdoors, aviation personnel also put themselves at the risk of exposure to flame retardant chemicals that are incorporated into the airplane’s materials. These chemicals are incorporated into various materials to prevent them from burning or starting a fire. As they are often used in the manufacturing of aircrafts, the chemicals can be found in the dust of commercial aircrafts. Many types of flame retardants exist such as tris(1,3-dichloro-isopropyl)phosphate (TDCPP) which is a known carcinogen. In a study published in 2013, researchers collected dust samples from 19 different commercial airplanes parked overnight and sent them to a lab to detect the presence of different flame retardant chemicals. In 100% of the dust samples, flame retardants, including TDCPP, were detected, posing a carcinogenic threat to those with high exposure to commercial aircrafts.
Another harmful condition that aircraft personnel subject themselves to is loud noise and whole-body vibrations. These factors account for most of a passenger’s discomfort during a flight and may also contribute to adverse health effects on one’s mental health and cardiovascular system, or lead to hearing loss. The primary cause for the constant loud noise heard on planes is the propulsion system, or propeller, of the aircraft’s engine. This noise coupled with whole-body vibrations felt via the aircraft’s seats could potentially promote DNA damage in the cells of frequent flyers.
A pair of studies performed by the same researchers tested for the frequency of sister chromatid exchange in the cells of different workers who were exposed to frequent noise and vibrations, specifically, in those of military aircraft pilots. The former study presented the earliest evidence that long-term exposure to these conditions – noise and whole body vibrations – do indeed have genotoxic effects in people. The later study performed on military aircraft pilots from the Portuguese Air Force corroborated these findings as their measured frequency of sister-chromatid exchange and cells with high-frequencies of sister-chromatid exchange (HFCs) were much higher than those of the tested ground-workers from the same air base. Therefore, it seems that discomfort in flight could actually be the body trying to convey an important message to protect itself from potential harm. As aforementioned, though the SCE technique does not directly label these agents as mutagenic or carcinogenic, its findings still serve as a very solid and significant point from which further research may be conducted.
These findings, of course, only reflect some of the major genotoxic hazards associated with the risks posed by frequent flying. Frequent flying amongst flight attendants has been linked with different types of cancer, including breast and prostate cancer, doubled risk for melanoma, as well as miscarriages in female flight attendants. Though these harmful effects of frequent flying have not been completely attributed to one direct source, current studies suggest cosmic radiation is the leading cause. Exposure to ionized radiation combined with other detrimental health effects brought upon by the irregular lifestyle habits of frequent flyers are still being studied and tested by scientists today. In terms of risk management, extra precautions and initiatives are being taken to maintain quality sanitary levels as well as manufacture radiation-resistant aircrafts that will hopefully act to ward off a significant amount of the harmful, toxic chemicals involved in commercialized air travel.
So as a frequent, but not that frequent aircraft passenger, you don’t need to worry too much about the damage done to your genome. Despite the risk being much greater at higher altitudes, the dose of cosmic radiation in flight is still relatively low, and only prolonged exposure to it amongst very frequent flyers and aircraft personnel has rendered these genotoxic results. Much of the literature suggests the need for further research and analysis, as many genotoxicity assays performed on this population have (thankfully) come back negative, despite speculation.