By Talya Danzer
Upon choosing aircraft transportation, there are many factors that must be taken into account. These factors include the risks of terrorist attacks, system malfunctions, and in the days of a pandemic, the risk of getting COVID-19; yet, it barely registers in one’s mind that there are risks of DNA damage and cancer due to factors such as cosmic ionizing radiation and ultraviolet rays. If these factors pose a risk to those who fly sporadically, then all the more so to pilots and flight crew whose job it is to maintain and fly in an aircraft daily.
Are the genotoxic risks of flying worth the paycheck and the sightseeing? Is one getting exposed to more than just beautiful sights?
Radiation is one of the main genotoxic risks that plague flight crew members. Cosmic ionizing radiation has two types to which flight crews are exposed. There is galactic cosmic radiation; radiation in which particles are emitted from the solar system and interact with Earth’s atmosphere and there are solar energetic particles, or solar flares. Compared to the average person who is exposed to around 0.33 mSv annually, aircrew are exposed to an annual amount of 3.07 mSv. Dosage exposure directly correlates with altitude, proving that the increased dosage intake in flight personnel is a result of the high altitudes reached when operating in an aircraft.
When exposed to copious amounts of cosmic radiation due to time spent in the air, there is an increased risk of DNA damage. The National Institute for Occupational Safety and Prevention used the comet assay to detect both single and double-stranded breaks in the DNA of aircrew in comparison to a control group of ground staff. Although the findings in this study lacked statistical significance, there was a noted increase in DNA damage in the aircrew members. These findings were solidified by an additional study done by the Department of Health Risk Analysis and Toxicology at Maastricht University. Using twenty-three flight engineers and a control group, there was a significant increase found in the oxidative DNA damage in the flight engineer’s peripheral lymphocytes. The increase of oxidative stress or oxidative DNA damage is often a biomarker for diseases such as cancer.
Cosmic radiation exposure leads to an increased risk of cancers including acute myeloid leukemia, skin cancer, and prostate cancer as well as reproductive issues. Skin cancer, such as melanoma, was discovered at higher rates in flight personnel. Despite this consistency, however, it is unclear whether the cancer diagnosis is due to increased cosmic ionizing radiation exposure on the aircraft itself or due to the increased leisure time of flight crew which, due to time in the sun, allows for an increase in ultraviolet radiation exposure. In pilots, chromosomal translocation, or the unusual arrangement of chromosomes, was discovered at statistically significant rates in relation to the amount of time they had been flying. This was done using FISH, or Fluorescence In Situ Hybridization, to help locate where the DNA is bound. The frequency of chromosomal translocation in those who had been flying for a long duration of time was double the frequency of those who had flown minimally. These chromosomal abnormalities are associated with cancer risk.
In women, there is an additional cancer risk: that of breast cancer. The exposure to cosmic radiation paired with the disruption of one’s circadian rhythm is a large contributor to the increased frequency of breast cancer observed in female flight crews. Using meta-analyses that comply with the meta-analysis of Observational Studies in Epidemiology guidelines, researchers were able to compile the statistical data from various scientific studies. Researchers were able to calculate a 95% confidence interval (CI), the range of values where a number likely exists, combined with the standardized incidence ratio (SIR). The SIR is the ratio of observed cancer cases over the expected number of cases. Results from ten separate studies analyzed in the meta-analyses indicate that compared to the general population, the SIR was 1.40. Since the number was larger than one, that indicates a greater number of cases than was expected. The study concluded that around 40% of these cases can be attributed to the disruption of the circadian rhythm in flight attendants as well as cosmic radiation exposure.
Circadian rhythm disruption significantly alters the immune system as well as hormonal balance. Being a member of the cabin crew ensures light exposure at night, short and unusual sleeping hours, as well as time zone changes. In women, this can increase the tumor growth rate for breast cancer. Melatonin, which mediates one’s circadian rhythm, inhibits breast cancer cell growth. The increase in tumor growth is due to the changes in melatonin release and cell metabolism. Mainly, the changes in circadian rhythm correlate with fatigue as well as mental health issues, none of which increase genotoxic risks.
Additionally, there are reproductive risks for crew members who are pregnant. Cosmic exposure as well as excessive standing time and heavy lifting may be linked to increased miscarriage rates during the first trimester. Targeting the exact cause of these reproductive problems is a work in progress, but one must be diligent to reduce their risks and exposure during pregnancy.
Flight crews greet passengers with big smiles and passengers are often jealous of an aircrew’s ability to travel the world and get paid to do it. Beneath the smiles, however, the DNA damage in flight attendants is nothing to be jealous of. Despite there being an influx of studies done on the effects of cosmic radiation on aircrews, the results indicate a need for further research. Cosmic and UV radiation are shown to not only damage DNA, but translocate chromosomes as well as increase the risk of certain types of cancer. Flight crews have a lot to consider when it comes to working in the skies. It is up to them to decide if the hazardous risk is worth the adventure this lifestyle brings. They may be the ones getting the paychecks, but it is their body that is paying the price.