Animal Cancer Rates Likely Driven By Human Activity, Scientists Claim

There’s no shortage of human activities that cause cancer. There’s cigarette smoking, the irresponsible spread of viruses, and radiation from bombs, just to name a few. These, as we know, all cause cancer in humans, but as a study published Monday in Nature Ecology & Evolution shows, our behaviors can cause cancer in many other species as well.

Humans, a team of international scientists claim in the paper are likely driving the increased cancer rate in multiple animal populations. They assert that we are an oncogenic species — one that causes cancer in other species.

“We know that some viruses can cause cancer in humans by changing the environment that they live in — in their case, human cells — to make it more suitable for themselves,” co-author and Arizona State University postdoctoral researcher Tuul Sepp, Ph.D. explained in a statement released Monday. “Basically we are doing the same thing. We are changing the environment to be more suitable for ourselves, while these changes are having a negative impact on many species on many different levels, including the probability of developing cancer.”

Take, for example, the Tasmanian devil population, which has been halved because of two forms of aggressive transmissible cancer since the mid-1990s. The disease is spread by biting and causes the formation of malignant tumors in and around their mouths, eventually causing the animals to starve. The scientists in the paper theorize that the population’s loss of genetic diversity — caused by human activities — is the reason why the disease is such a potent killer. And Tasmanian devils, of course, are not the only species being affected.

This paper, more than a traditional study, serves as a rallying call for scientists to dive into the subject. Cancer in wild populations, the authors say, is a “completely ignored topic,” despite the growing evidence that our species influences the prevalence of the disease. It’s obvious that human activities affect animal environments: Now, the scientists argue, we have to consider how the factors that cause cancer formation in humans could very well be causing cancer in animals as well.

“Cancer rate has been found in all species where scientists have looked for it and human activities are known to strongly influence cancer rate in humans,” Mathieu Giraudeau, Ph.D., also a ASU postdoctoral researcher, said in the statement. “So this human impact on wild environments might strongly influence the prevalence of cancer in wild populations, with additional consequences on ecosystem functioning.”

Another example is the beluga whale population that lives in Canada’s St. Lawrence River estuary, for whom intestinal cancer is the second-leading cause of death. This disease rate is so high that scientists in 2002 called it the highest rate of cancer of any wild mammal species. Since the belugas that live further north in the Canadian Arctic don’t suffer from cancer, scientists believe that the root of the illness is proximity to humans. Industrial, chemical-filled pollution is known to wash into the St. Lawrence River estuary, and the humans who live near it have high rates of cancer in their digestive system as well.

Chemical pollution, the paper’s authors write, is just one of the ways human activity is driving cancer rates. The accidental release of radiation into the atmosphere, the accumulation of micro-plastics in land and water environments, exposure to pesticides and herbicides, and artificial light pollution are all potential culprits. These factors have previously been connected to cancer growth in humans — now it’s time to statistically prove that they affect animal cancer as well.

“The next step is definitely to go into the field and measure cancer rate in wild populations,” said Giraudeau. “We are now trying to develop some biomarkers to be able to study this. I think it would be interesting to measure cancer prevalence in wild animals in human-impacted environments and also in more preserved areas for the same species.”