Cancer and the Climate: Concurrent Trends

 Samuel Schradin

Cancer and the Climate: Concurrent Trends

            Cancer etiology has been a multifaceted and debated topic, often overlooking the disastrous effects of climate change. With the incidence of cancer diagnosis on the rise, the external factors of our environment play a seemingly larger role on the overall public health than once thought. Stronger storms, rapidly spreading wildfires, the slow degradation of the Earth’s ozone layer, and many other consequences of climate change often correlate to the known causes of cancer. Environmental shifts from our warming planet have led to increased exposure to malignant cancer-causing carcinogens and risk-factors.

A prevalent case to look at would be the increased rates of skin cancer, more specifically melanoma, within our society. According to the American Academy of Dermatology Association, “Melanoma rates in the United States have been rising rapidly over the past 30 years — doubling from 1982 to 2011 — but trends within the past decade vary by age. There has been a 31.5% increase between 2011 and 2019.” [1]. This increase runs concordantly to the rate of depletion in the ozone layer. The ozone layer, a thin layer of gas in the stratosphere, functions as a shield to absorb the sun’s ultraviolet rays (UV-B). Without this, life on Earth would not be possible, as direct exposure to UV-B cripples and destroys the DNA in living organisms. 

Many man-made processes and products release harmful gasses into the atmosphere, contributing to the destruction of the ozone layer. Chlorofluorocarbons and other halogenated ozone-depleting substances, gasses with a carbon base, are the main contributors to this issue. According to the United States Environmental Protection Agency, “Once released at Earth’s surface, they [chlorine and bromine] eventually migrate upwards to the stratosphere, where ultraviolet (UV) radiation from the sun converts them into reactive gasses that destroy ozone. By the 1980s, it was clear that these ozone-depleting substances (ODS) were indeed having a significant impact on stratospheric ozone…” [2]. 

Figure 1: UV affecting the layers of skin [3]

Most cases of skin cancer are due to overexposure to UV. As depicted in Figure 1, UV penetrates through the surface layers of the skin and into the epidermis and dermis. The epidermis and dermis function as the safety and repair systems for the skin. The epidermis, when exposed to too much UV, can experience rapid cellular decay and oxidative stress. The skin cells in this layer cannot repair their DNA correctly, leading to a higher chance of mutations. Mutations like these can lead to basal cell carcinoma, and many other forms of skin cancer. Remedying this issue requires the immediate limitation of the use of halon and carbon based gasses, as this is necessary to preserve our ozone layer.

Climate change continues to be a worsening issue, perpetuating the rise of cancer not only through the depletion of our ozone layer, but with other atmospheric effects as well. One such effect is global warming. As the planet grows warmer, so do the intensities of extreme weather phenomena. Hurricanes, for example, have seen significant increases in their destructive potential. The Center for Climate and Energy Solutions writes that, “...the number of major hurricanes has increased while the number of smaller hurricanes has decreased. Based on modeling, the National Oceanic and Atmospheric Administration predicts an increase in Category 4 and 5 hurricanes, alongside increased hurricane wind speeds. Warmer sea temperatures also cause wetter hurricanes, with 10-15 percent more precipitation from storms projected,” [4]. Wetter hurricanes cause more flooding, which leads to more destruction. Chemical plants, manufacturing sites, and even peoples homes, contain copious toxic chemicals and waste that are exposed to the environment by flooding. Chemicals that lead to an increased risk of cancer, such as dioxins, are commonly found in the sewage systems affected by hurricane flooding. Dioxin can linger in the environment for decades, and has been linked to increased rates of Hodgkin’s and non-Hodgkin’s lymphoma, lung, prostate, and liver cancer. The repeated flooding will continue to get worse as the intensity of the storms do, leading to more debris and environmental poisons being exposed to humans, animals, and plants alike. We will continue to see an upwards trend in cancer diagnosis in flood-risk areas as storms continue to get worse.  

Figure 2: Long Beach Island streets full of debris after Hurricane Sandy [5]

Although we will see larger storms as the planet warms, we will also see a decrease, or close to stagnation, in the overall amount of smaller storms that occur. Droughts and dry weather caused by this lack of rain lead to more wildfires. According to the National Cancer Institute, “...climate change-related disasters can expose people to cancer-causing substances, or carcinogens, in the environment. Wildfire smoke contains several carcinogens, such as formaldehyde and benzene,” [6]. Lung and brain cancer have been linked to these two carcinogens [formaldehyde and benzene], and have shown an increase in incidence among residents who live near these wildfires. Shown below in Figure 3 is a 20 year study (2002-2022) conducted by Jill Korsiak of McGill University. The chart below details the increased incidence of several cancers among residents within a certain radius of wildfires. The study concluded that those who lived in affected areas for a duration of 10 years or longer had a 10 percent increase in cancer incidence as a direct result of the wildfires. Extreme conditions such as these wildfires, hurricanes, and many other increasingly-occurring phenomena caused by climate change have repeatedly shown consequences that lead to a direct increase in the incidence of cancer. 

Figure 3: Adjusted associations between categories of area burned[7]

The relationship between climate change and cancer incidence cannot be overlooked for much longer. A direct correlation between two of the larger issues our planet faces, an increase in degenerative diseases and an environment rapidly turning inhospitable, have shown their disastrous effects to us. However, we can take solace in the fact that a remedy to climate change helps both of these issues. Efforts to repair the ozone layer have shown much promise, with some experts estimating a healthy recovery by 2065. Hopefully, with enough effort and prioritization, we can curb the looming threat of climate change, and the increased incidence of cancer it causes.  

References

[1]https://www.aad.org/media/stats-skin-cancer#:~:text=Melanoma%20rates%20in%20the%20United,past%20decade%20vary%20by%20age. 

[2]https://www.epa.gov/ozone-layer-protection/information-ozone-and-ozone-depletion

[3]https://www.cancerresearchuk.org/about-cancer/causes-of-cancer/sun-uv-and-cancer/how-does-the-sun-and-uv-cause-cancer#:~:text=Too%20much%20UV%20radiation%20from,Anyone%20can%20develop%20skin%20cancer.

[4]https://www.c2es.org/content/hurricanes-and-climate-change/

[5]https://www.app.com/picture-gallery/news/local/monmouth-county/sandy-recovery/2017/10/20/superstorm-sandy-images-of-heartbreak-and-hope/106848044/

[6]https://www.cancer.gov/news-events/cancer-currents-blog/2023/cancer-climate-change-impact#:~:text=For%20instance%2C%20climate%20change%2Drelated,Change%20and%20Cancer%20Working%20Group.

[7]https://www.thelancet.com/journals/lanplh/article/PIIS2542-5196(22)00067-5/fulltext#fig3