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June 2020 (Vol. 5 Issue 4)

Chemical Kitties

About the author: 

Chemical Kitties image

We may inadvertently be contaminating our pets with a slew of toxic chemicals at high doses, according to an environmental group

We may inadvertently be contaminating our pets with a slew of toxic chemicals at high doses, according to an environmental group.

Research by the non-profit Envi-ronmental Working Group (EWG) discovered that a sampling of pet dogs and cats were polluted with 48 of 70 industrial chemicals tested, which included chemicals used in plastics and food packaging, stain-proofing chemicals, heavy metals and fire retardants. In fact, the animals were contaminated with high levels of many of the same chemicals recently found in people.

Not only does this suggest poten-tial harmful consequences for their health, but it also shows that dogs and cats may be serving as involuntary sentinels of human health problems that are increasingly being linked to chemical contamination.

The EWG study, which it says is the most comprehensive investigation into the chemical body burden of companion animals conducted to date, analyzed samples of blood and urine from 20 dogs and 37 cats collected at a veterinary clinic in Virginia. Although this research was carried out in the US, the results are likely to apply to the UK and other countries, as most of the chemicals studied are commonly found in homes across the globe.

In dogs, a total of 35 chemicals were detected, including stain- and grease-proof chemicals (perfluoro-chemicals in the Teflon family), plastics chemicals called phthalates and fire retardants called PBDEs (polybrominated diphenyl ethers). The contaminants included 11 known carcinogens, 31 chemicals toxic tothe reproductive system and 24 neurotoxins. As for cats, 46 chemicals were detected, including nine carcino-gens, 40 chemicals toxic to the reproductive system, 34 neurotoxins and 15 chemicals toxic to the endocrine system. Compared with people, cats showed especially high levels of PBDEs and methylmercury, a toxic pollutant from coal-based power plants and a common seafood con-taminant (see for more information).

Risks to health

For many of the chemicals included in the study, health risks in companion animals have never been investigated. However, laboratory research and human data tie them to a number of serious health effects. Mercury, for instance, causes blurred vision, hear-ing problems, paralysis, numbness and loss of memory in high doses, and even low levels are associated with preterm births and an increased risk of heart attack (see WDDTY vol 17 no 10). Phthalates-found by the EWG in high amounts in both dogs and cats-are also toxic and have been linked to hormonal abnormalities, birth defects and reproductive problems in humans (see WDDTY vol 19 no 1, page 20).

One group of chemicals that has been studied in pets is PBDEs, known to be hormone disruptors. A recent small-scale study by the US Environ-mental Protection Agency (EPA) found extremely high levels of PBDEs in cats, supporting the EWG findings.

The researchers suggested that exposure to these toxins could be the cause of feline hyperthyroidism (overactive thyroid), a leading cause of illness in older cats (Environ Sci Technol, 2007; 41: 6350-6). Indeed, average PBDE levels were three times higher in older cats with hyperthyroidism than in younger cats without the disease, although the difference was not statistically significant because of high variability within each group (Environ Health Perspect, 2007; 115: A580).

The study also noted that the incidence of feline hyperthyroidism has increased dramatically over the past 30 years, coinciding with the growing use of PBDEs in household products.

In addition to PBDEs, the plastics chemical and endocrine disruptor bisphenol A (BPA)-known to leach into tinned cat food from the tin inner lining-may also be linked to feline hyperthyroidism (Res Vet Sci, 2002; 73: 177-82). Consumption of canned (vs dry) foods puts cats at greater risk for the disease (J Am Vet Med Assoc, 2004; 224: 879-86; J Vet Intern Med, 1999; 13: 323-9).

Teflon, or polytetrafluoroethylene (PTFE), is also associated with adverse effects in pets. Teflon toxicosis, or 'polymer fume fever', is a respiratory condition affecting birds in particular. It happens when noxious fumes are emitted from overheated cookware coated with the 'non-stick' plastic PTFE. In one case, five cockatiels died within 30 minutes of a PTFE-coated frying pan being accidentally over-heated and, within the hour, their owner also developed symptoms of polymer fume fever (Vet Rec, 1975; 96: 175-8). PTFE emissions also caused "acute respiratory distress and rapid death" in exposed budgerigars (Am J Vet Res, 1982; 43: 1238-42).

In people, Teflon can cause birth defects, cardiovascular effects and certain types of cancer (see WDDTY vol 16 no 8).

Other chemicals of concern

A number of other chemicals not included in the EWG analysis could pose health risks for our pets. Indeed, the group reviewed three decades of the scientific literature, and found scores of links between chemical exposures and pet illnesses.

Most notably, household pesticides have been linked to certain types of cancer in dogs and cats. The use of topical insecticides-such as flea- and tick-dip products-was associated with an increased risk of bladder cancer in dogs. With one or two applications a year, the risk increased by 1.6 times, while more than two applications a year increased the risk by 3.5 times (J Toxicol Environ Health, 1989; 28: 407-14).

Use of flea-control products are also associated with oral squamous cell carcinoma (SCC) in cats. Cats that wore a flea collar had five times the risk of oral SCC as non-wearers (J Vet Intern Med, 2003; 17: 557-62).

Herbicides are another concern. The risk of bladder cancer was significantly higher among dogs exposed to lawns or gardens treated with either herbicides and insect-icides (7.2 times increased risk) or with herbicides alone (3.6 times increased risk), compared with dogs not exposed to such treated lawns(J Am Vet Med Assoc, 2004; 224: 1290-7). There's also a strong link between exposure to the common herbicide 2,4-dichlorophenoxyacetic acid (2,4-D)-associated with non-Hodgkin's lymphoma in humans-and canine malignant lymphoma (J Natl Cancer Inst, 1991; 83: 1226-31).

Our pet sentinels

Clearly, pets inhale, ingest and absorb environmental pollutants just as humans do, and they can suffer acute and chronic health effects from such exposures.

As the EWG points out, its research not only highlights the need to protect our pets (see box above), but also informs our understanding of our own health risks.

Companion animals have been recognized as natural sentinels of chemical hazards to human health for centuries (Environ Health Perspect, 1997; 105: 1312-9). Their shorter lifespans and more rapid ageing means that any health problems they suffer as a result of chemical exposures appear much earlier than in people. Moreover, pets' behavioural patterns (living closer to the ground, chewing on domestic objects, licking and self-grooming, ingesting dust) are similar to those of human toddlers (Environ Health Perspect, 2007; 115: A580).

For this reason, says the EWG, toxic pollutants in pets "sounds a cautionary warning for the present and future health of children".

Joanna Evans

How are pets exposed?

EWG researchers found that the average levels of many chemicals were significantly higher in pets than in people, with 2.4 times higher levels of stain- and grease-proof coatings (perfluorochemicals) in dogs, 23 times more fire retardants (PBDEs) in cats, and more than five times the amounts of mercury (see But how are pets exposed to these and other such chemicals?

- Dogs that eat scraps from the floor can swallow dust brought in from outdoors that is contaminated with heavy metals or pesticides

- Cats can ingest chemicals that leach into cat food from the inner coatings of the catfood tins

- Pets playing in the garden can inhale or ingest herbicides used on the grass

- Cats can consume high amounts of mercury from fish-based foods

- Chew toys can contain plastic-softening chemicals

- Foam beds can be coated with fire retardants and stain-proofing chemicals

- Plastic water bowls can leach hormone-disrupting chemicals into their contents.

Protecting your pet

- Choose pet foods carefully. Avoid tinned food and vary your cat's diet to limit its exposure to mercury from seafood. Avoid anything with the preservatives butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT) and ethoxyquin, which can be toxic to animals (Neurobehav Toxicol Teratol, 1981; 3: 321-9; J Nutr, 1991; 121: S163-4). See WDDTY's booklet What Vet's Don't Tell You for more advice on selecting the best food for your pet, or log on to and read our road test on natural pet foods.

- Use filtered water to fill your pet's water bowl, and choose a bowl that's not made of plastic.

- Vacuum regularly with a HEPA-filter vacuum to limit your pet's exposure to toxic chemicals in house dust. In addition, remove shoes

at the door, or use doormats, to avoid tracking pesticides and other contaminants indoors from outside.

- Replace older foam pet bedding, and replace or reupholster furniture with exposed or crumbling foam in which flame retardants are found.

- Don't opt for stain-proof treatments on couches, carpets and car upholstery as they're full of toxic perfluorochemicals.

- Avoid non-stick pans. An overheated non-stick pan can release toxic chemicals that may be deadly to pets and harmful to humans.

- Avoid flea collars and topical insecticides. Instead, vacuum often and bathe your pet regularly. Adding a few drops of tea tree oil to a herbal shampoo helps to repel fleas, and aids healing of the pet's flea-bitten skin. For pets resistant to baths, mix a teaspoon of tea tree oil in a cup of water and spray the mixture onto the animal's fur. Boosting your pet's immune system will also help to control fleas. Make sure its diet contains adequate amounts of calcium, magnesium, potassium, phosphorus and zinc, as well as plenty of B vitamins, which are natural flea and tick repellents. Brewer's yeast and rice bran contain high levels of all the B vitamins. Adding garlic to your pet's diet may also help (Townsend Lett, 2003; 237: 36-8).

- Care for your garden without using herbicides or insecticides. Avoid using pesticides inside the home as well. For non-toxic alternatives, see WDDTY vol 19 no 2.

- Visit for more helpful tips.

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