Pollution and Environmental Cancer Causes

Environmental Causes of Cancer

Environmental pollutants are known to influence the development of cancers in humans. But we also share our living spaces with our dogs, and they develop many of the same cancer types as humans.

Because of this, our dogs are also at elevated risk for certain cancer types from living in areas with excessive air and water pollution.^1,2 There is also pollution inside the home, so even dogs kept indoors may be exposed to household pollutants. In fact, they may even have a slightly higher risk than their owners, who spend time away from the home.¹²

Pollutants Suspected to be Carcinogens

There are many pollutants out there that we know or suspect increase the risk of cancer development.

Tobacco Smoke

For dogs who live with cigarette smokers, a weak association has been established between tobacco smoke exposure in the home and nasal cancers. The risk appears to rise for dogs with medium length and long noses.¹²

In general, veterinarians do not recommend smoking any substance, including marijuana or vaping, around dogs.

• According to the CDC, marijuana secondhand smoke contains many of the same toxins found in cigarettes, and some in higher amounts.¹⁶
• According to the American Heart Association, secondhand vape mist poses a similar risk to cigarettes, with heavy metals and known carcinogens such as benzene being delivered via the ultrafine particles.¹⁷

Coal and Kerosene

Dogs have an increased risk of getting cancer of the lung and nasal cavity if living around coal burning sources and kerosene heaters.¹² This is obviously a health risk for humans, too.

Pet dogs may even serve as “sentinels” that human members of the household are also at risk.⁵ Sentinels in the armed forces watch out for danger so the company is ready when it arrives. In a medical sense, sentinels are animals that experience trouble before their human companions do. Both dogs and cats are considered sentinel animals for humans, which means if cancer risks rise for them, they are probably also rising for us. The canaries in the coal mines were literally used as sentinel animals.

Drinking Water Contaminants

Tap water contaminants may contribute to increased incidence of bladder cancer (urothelial carcinoma) in dogs.⁷

Water Disinfectants

Trihalomethanes are by-products produced during water treatment. Unfortunately, exposure to these disinfection chemicals in tap water may increase the risk of bladder cancer in humans, and most water filters don’t catch them. This may not be true for bladder cancer in dogs at the concentrations they ingest.⁸

Air Pollution, Acid Rain, and Smog

Research has found that Boxers with lymphoma are more likely to live in counties exceeding the EPA’s ozone limits for air pollution.⁷ This suggests that pollution may be one of the causes of lymphoma in dogs.

Lead, benzene, and asbestos are few of the common air pollutants that have been identified as carcinogens.^11,15

Insecticides

Canine bladder cancer (urothelial carcinoma) and lymphoma are associated with the use of insecticides in the household (and also with living in areas with high industrial activities).^1,2

Scottish Terriers in particular are known to be at a higher risk of developing bladder cancer. However, a study showed that using flea and tick products containing fipronil or imidacloprid did NOT show an increased risk of transitional cell carcinoma.¹⁰ These products, which are approved for use in dogs, are generally safer than insecticides intended to be used in the house or yard.

Herbicides

Study results suggest that exposure to lawns or gardens treated with herbicides was associated with an increased risk of bladder cancer in Scottish Terriers. Owners of Scottish Terriers should limit their dogs’ access to lawns or gardens treated with herbicides such as Roundup and 2,4-D.⁹

Perfluorochemicals (PFCs) and Polybrominated Diphenyl Ethers (PBDEs)

PFCs are a synthetic compound common in stain, grease, and water repellants for furniture, fabrics, and kitchenware.⁴ PFCs are associated with cancers in mice and rats.⁴

PBDEs are flame retardants used in furniture cushions and many synthetic fabrics. They are also used in the outer plastic housing of many common household goods like televisions and computers. PBDEs have been linked to significant defects in lab animals including thyroid and liver tumors in rodents and decreased immune function in marine mammals.⁴

Research in dogs is still early, but toxicologists at the Environmental Working Group in Washington, D.C. have done an initial study looking into these chemicals and their effects on dogs. The team analyzed blood samples from 20 pet dogs and found that pooled dog samples showed high levels of PBDEs and PFCs.⁴ More research will need to be done to determine how these levels can impact cancer risk.

Vinyl Chloride

Vinyl chloride is a colorless gas that is released during the production of polyvinyl chloride (PVC) and vinyl. Vinyl chloride is a known carcinogen. Humans and dogs can be exposed to vinyl chloride through the air if they live near a facility that manufactures PVC or vinyl products or through contaminated groundwater.¹³

Asbestos

Although a very rare form of cancer, dogs can develop primary lung cancer and mesothelioma after long term exposure to building materials containing asbestos. Dogs owned by people who worked in the asbestos industry are at greater risk for developing mesothelioma, likely because people have asbestos on their clothing when they come home from work.¹⁴

Does Pollution Always Cause Cancer?

It is likely that a combination of environmental and genetic factors contribute to the development of most cancer types in dogs.¹ One single exposure is unlikely to cause cancer on its own.

Development of cancers after exposure to environmental pollutants is dependent on multiple factors, including:

• the type and concentration of the contaminant
• length of exposure
• the ability to neutralize the chemical once inside the body

Enzymes in a dog’s liver like glutathione-S-transferase (GST) assist in deactivating environmental hazards and preparing them for safe excretion from the body. In people, there are variations in GST enzymes due to genetic differences, and so their capacity to deactivate environmental hazards is also different. Two people exposed to the same pollutant may have different risks of developing cancer because of genetic differences in GST and other detoxifying enzymes.³

Pollution is more likely to contribute to cancer risk if your dog lives in an area with a lot of environmental pollution, especially if he also has other risk factors for developing cancer.

Risk Factors

Several risk factors can increase the chance that your dog might develop cancer because of pollution:

• Prolonged exposure to environmental pollutants, even in small amounts
• Living in or near industrial areas
• Chewing non-edible items that contain carcinogens
• Breed or mix of breeds with genetic cancer risk, such as Golden Retrievers or Boxers
• Living with a smoker
• Living near agricultural areas
• Immune system disorders

No single risk factor is likely to cause cancer by itself. However, having multiple risk factors can increase your dog’s risk.

How to Reduce Pollution Risk

Increased awareness about chronic household exposures to pollutants is important for dog lovers. While you can’t control everything, there are steps that you can take to counteract risk. Minimizing exposure to pollutants may help in decreasing the occurrence of certain cancers.³

Here are some things to consider:

• Enlist help to stop smoking or help a family member stop smoking.
• Reduce or eliminate the use of herbicides, especially if you have a Scottish Terrier.
• Reduce or eliminate the use of insecticides.
• Filter drinking water, especially if you live in an area with a lot of industrial activity.
• Use an air purifier in your home, especially if you live in an area with a lot of industrial activity.
• Replace furniture and rugs containing synthetic flame retardants. Some naturally flame-resistant alternatives include wool, cotton, and hemp.
• Choose products that have not been treated with water and stain repellants, especially if your dog is a chewer.
• Replace plastic dog bowls with ceramic or metal bowls.
• Avoid the use of coal and kerosene heaters.
• Move away from areas with a lot of pollution if possible, and support legislation that regulates manufacturing and other sources of pollution.