The Common Threat
Tasmanian devils, Beluga whales and Green sea turtles all share a new and common threat to their conservation. These animals and many more are dying from cancer at astonishing rates, and human pollutants are major contributors to the cancer’s severity and prevalence.
Cancer is well-documented as one of the current leading concerns for human health and takes the lives of about ten percent of humans. This dangerous disease has now jumped species, killing many wild animals at rates similar to those found in humans. Wildlife cancer is a global phenomenon seen in different habitats and varying types of animals, especially marine animals. It is also cause for concern because animals in natural habitats are not easily tracked or treated.
Animals are progressively more at risk for extinction because of toxins released from human waste and pollution. For example, Beluga whales are contracting intestinal cancer from the polluted water in the St. Lawrence River waterway in Canada. The pollution in the water contains a well-known human carcinogen (polycyclic aromatic hydrocarbons) affecting fish that humans eat, not just the whales.1
Polycyclic aromatic hydrocarbons (PAHs) are found in several compounds that could be related to ocean pollution. PAHs are most commonly found in high concentrations in automobile exhaust and industrial emissions.2 The contamination can be absorbed through the scales of fish or other marine wildlife.
A convincing example of the high correlation between human pollutants and wildlife cancer is the California sea lion. Studies by the U.S. Environmental Protection Agency, released in June 2009, suggest that the air in over 600 cities in the United States pose cancer risks. One of the cities with the highest amount of trapped carcinogens is Los Angeles, California.3 This pollution does not just stay in the air over California. It gets blown off the coast, and enters the ocean through rain. The sea lions encounter the polluted rain when they bathe daily in the polluted areas of the ocean.
The Marine Mammal Center of California found 18 percent of sea lions studied postmortem had cancerous tumors. Scientists have been unable to make reliable estimates about the total numbers of live infected sea lions because the animals are in the wild, but they assert this is an extremely high rate of cancer for wild animals.4
There are similar cases occurring worldwide in land and sea animals, which is worrying for human and animal pathologists. Although these cancers are virus-induced, they are exacerbated in prevalence and severity because of human pollutants evidenced by the high increase in cases.
The fact that human pollution has spread to oceans and hurts animals is not new, but many more countries are being hit. The risk of species extinction rises as pollution worsens in developing countries. Scientists are also worried about the impossibility of reducing this trend without major habitat relocation for many species.
Habitat relocation is already occurring for several species with viral cancers. The most notable case of this is the Tasmanian devil.5 The form of tumor found on the faces of Tasmanian devils spreads through contact with other devils, usually through biting and fights. To reduce the spread, scientists are relocating and isolating cancer-free Tasmanian devils. Relocation is problematic because it can cause damage to ecosystems worldwide, if it remains the only conservation measure against the spread of viral cancers. Many of the animals are moved into unfamiliar surroundings and zoos, where their society is severely disturbed.
In the case of many marine animals, isolation is not a feasible solution. The Green sea turtle contracts fibropapillomatosis, tumors of the skin and internal organs.6 These animals, a global migratory species, cannot be isolated or relocated. The disease has global consequences for these animals and others that come in contact with migrating turtles.
Migrating wind and ocean patterns affect the global spread as well. As noted earlier, human pollutants in the air and water do not stay in a single area. Weather patterns are global, not local. There are already concerns about pollution from the coal plants in China being blown into the coast of the United States, and vice versa. In the ocean, harmful chemical run-off, like PCBs and pesticides, can be washed up on shores worldwide, due to tidal movements.
Currently, there are international laws to decrease physical and territorial injury of animals by humans, but what about this more indirect danger? Tougher carbon emissions and pollution laws, like the Kyoto Protocol, are one step that can reduce the pollution entering waterways worldwide. The problem with these treaties is that they do not directly address animal conservation and the treaties are not very strong or enforceable. In fact, China, one of the world’s biggest polluters, continually refuses to agree to binding limits on carbon emissions.
Scientists point to the necessity of increased monitoring in order to care for the situation immediately because of the threat posed to both wildlife and humans. Rapid extinction could follow from continued pollution and viral spread of cancers. Also, humans draw upon several of the animals most affected by cancers for food and exports, like English Sole fish and certain types of catfish.
The One World One Health initiative highlights the need for more monitoring of animal diseases for conservation and knowledge purposes.7 A positive aspect of studying cancer in animals is a greater understanding of human cancer. In light of the Tasmanian devil transmissible cancer, we can gain a much greater understanding of the relationship between cancer and the immune system and evolving, transmissible cancers.8
The significance of this new threat to animals offers a chance to refocus conservation policy and efforts for human and animal benefit. Human and animal DNA and make-up are extremely similar, so the study of cancer in one is beneficial for both. The main author of the report “Wildlife Cancer: a conservation perspective” explains the necessity of curbing animal cancer, “Animals act as sentinels….From them, we might get a clue whether there’s something in the environment to look at….”9
Sea lions have a similar diet to humans. If they are getting cancer from toxic compounds they ingest, we are alerted to the possibility of toxins in our food chain. The health of one type of animal clues humans into the health status of other types of animals and plants within the same territory or food chain. By understanding the causes of threats to animals and ecosystems we can better understand threats to our own global health, impending issues with our resources, and how to better care for the global community.
The choices of developing and developed countries concerning pollution and waste reduction will directly affect animals worldwide. Even simple steps taken in homes to use green cleaning products, or China’s recent 66 percent reduction in the use of plastic bags (40 million bags per year), can keep thousands of gallons of toxins out of waterways.
To Learn More:
McAloose, Denise and Alisa L. Newton. “Wildlife Cancer: A Conservation Perspective.” Nature Reviews Cancer, July 2009.
Spyros, George. “Fabien Cousteau Part 1: Ocean Exploration, Industry and You.” Tree Hugger TV. June 8, 2009.
1 Wildlife Conservation Society. “Wildlife Faces Cancer Threat.” Wildlife Conservation Society. June 24, 2009.
2 “Chemical Fact Sheets: Polycyclic Aromatic Hydrocarbons.” Wisconsin Department of Health Services. October 24, 2008.
3 Capiello, Dina. “EPA Says Air Pollution In 600 Neighborhoods Poses Cancer Risk.” Huffington Post. June 24, 2009.
4 “Herpes, Genes and PCBs are Factors in Cancer in California Sea Lions.” The Marine Mammal Center. February 18, 2006.
5 Lepisto, Christine. “Cancer Threatens Wild Animal Populations.” Tree Hugger. June 24, 2009.
7 Wildlife Conservation Society. “Wildlife Faces Cancer Threat.” Wildlife Conservation Society. June 24, 2009.
8 “Cancer in Wildlife Videocast.” Museum of Science. June 24, 2009.
9 Peeples, Lynn. “Cancer Joins Threats to Wildlife.” Scientific American. June 24, 2009.
* Pictures: http://www.flickr.com/photos/richardfisher/3136981421/sizes/m/ and Wildlife Conservation Society.