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A carcinogen is any substance that can cause cancer. Your pet may encounter carcinogens by consuming certain foods, medications, lifestyle factors, or other environmental exposures. Experts have classified over 500 substances as definitive, probable, or possible carcinogens. Carcinogen identification is critical for limiting your pet’s exposure. Several factors influence whether a carcinogen will lead to cancer in pets, including the extent and duration of carcinogen exposure and the pet’s genetic background.

How does a carcinogen cause cancer?

Carcinogens can cause cancer by interacting with DNA, disrupting the function of cells.  DNA damage occurs when its sequence changes, leading to a mutation. Mutations can cause uncontrolled cell division or prevent regulated cell death. The unrestrained cell division ultimately leads to the formation of a tumor, which may spread to other parts of the body, causing cancer. This spread is known as metastasis.

Carcinogens, cancer, and your pets

Many chemicals have made their way into our homes to make our lives easier and more efficient. For example, we find them in our kitchens (triclosan in antibacterial soap), laundry (sodium lauryl sulfate in soap), backyard (pesticides), and even our wardrobes (dyes, formaldehyde). However, certain chemicals can be carcinogenic that may be harmful to you and your four-legged friend. The table below lists what chemicals may increase your pet’s cancer development risk.

Table 1. Categories of substances that can affect your pet’s risk of cancer

Agent Examples
Infectious agents some viruses
Medical radiation X-ray
Ultraviolet light sun exposure, tanning beds
Pollutants engine exhaust, fire smoke, tobacco smoke, power plant pollutants
Chemicals asbestos, nickel, cadmium, radon, vinyl chloride, benzene


How are carcinogens identified?

Researchers use the following ways to identify a carcinogen:

    1. Molecular structure analysis:  Researchers compare chemical structures to previously identified carcinogens.
    1. Epidemiological studies: Scientists look at population data to see if there is a correlation between exposure to a substance and cancer.
    1. Laboratory tests: Scientists expose cells or lab animals to a suspected carcinogen and observe cancer incidence.

It is important to note that laboratory studies are experimental investigations conducted in a controlled setting with predetermined variables of interest, including the dose of treatment.

To induce cancer in an experimental setting, researchers may expose animals to either a fake treatment (placebo) or a range of doses that include low, medium, or high amounts of the chemical of interest. Studies should show how these doses translate to real-world conditions and how the results impact your pet. It is also important to consider the following:

    1. What the study is assessing, such as variables, endpoints, and outcome.
    1. The study design, such as how the chemical is administered and for how long.
    1. The strain of cells or breed of animal used.
    1. Conclusions of the study.
    1. Whether these results are consistent with those from other peer-reviewed published studies.

If you find a study demonstrating a substance as a carcinogen, consider reducing your pet’s exposure to the chemical to minimize the risk of cancer development.

What are the regulating bodies?

There are several international and national health agencies that determine whether a substance is officially categorized as a carcinogen to humans. The International Agency for Research on Cancer (IARC) regularly publishes updated lists of substances that are carcinogens in humans. The U.S. Environmental Protection Agency assesses the risks of substances and classifies them by their potential to be a carcinogen. Lastly, the U.S. National Toxicology Program also publishes updated reports on chemicals and substances that may pose a carcinogenic risk.

Unfortunately, there are no agencies that focus specifically on carcinogens in pets. But, while these agencies focus on the risk to humans, there is a high chance that the substances they identify as harmful will affect your pet in a similar way. If a substance is listed on the reports from these agencies, it is safer for you to limit your pets’ exposure.

Putting your knowledge to use

Because our pets share our living environment, the same carcinogens can affect them. However, you might also find harmful substances in pet products, such as food, medications, and pet supplies. Put your knowledge to practice by looking into what products you want to use with your pet. You can start by:

    • Reading the labels on your pet’s products (food, shampoo, toys, etc.)
    • Research any unfamiliar substances
    • Reduce your pet’s exposure to potential carcinogens
    • Talk to your vet about carcinogen exposure

Sifting through all the reports on potential pet carcinogens can be challenging. However, as more research offers us a greater understanding of cancer and pets, we can ensure our pets live long, healthy, and cancer-free lives.

The Pet Cancer Foundation’s Website Editorial team is comprised of veterinarians, veterinary oncologists, and veterinary technicians, as well as scientific writers and editors who have attained their PhD’s in the life sciences, along with general editors and research assistants. All content found in this section goes through an extensive process with multiple review stages, to ensure this extended resource provides pet families with the most up-to-date information publicly available.

The team listing of those contributing to the information on this page is here:

Keep Your Pets Healthy Editorial Team

Last Updated: August 6, 2022

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The following sources were referenced to write the content on this page:

Andrade, FH, Figueiroa, FC, Bersano, PR, Bissacot, DZ & Rocha, NS 2010, ‘Malignant mammary tumor in female dogs: environmental contaminants’, DiagnPath, vol. 5, no. 45, pp.1-5.

Barnes, JL, Zubair, M, John, K, Poirier, MC & Martin, FL 2018, ‘Carcinogens and DNA damage’, Biochem Soc Trans, vol. 46, no. 5, pp.1213-1224.

Cogliano, VJ, Baan, RA, Straif, K, Grosse, Y, Secretan, MB, Ghissassi, FE & Kleihues, P 2004, ‘The science and practice of carcinogen identification and evaluation’, Environ Health Perspect, vol. 112, no. 13, pp.1269-1274.

Sévère, S, Marchand, P, Guiffard, I, Morio, F, Venisseau, A, Veyrand, B, Le Bizec, B, Antignac, JP and Abadie, J 2015, ‘Pollutants in pet dogs: a model for environmental links to breast cancer’, Springerplus, vol. 4, no. 27, pp.1-11.

Takashima-Uebelhoer, BB, Barber, LG, Zagarins, SE, Procter-Gray, E, Gollenberg, AL, Moore, AS & Bertone-Johnson, ER 2012, ‘Household chemical exposures and the risk of canine malignant lymphoma, a model for human non-Hodgkin’s lymphoma’, Environ Res, vol. 112, pp.171-176.

The Pet Cancer Foundation’s medical resource for pet owners is protected by copyright.

For reprint requests, please see our Content Usage Policy.