When the Environmental Working Group in the United States tested pets in 2008, dogs and cats tested positive for 48 out of 70 industrial chemicals. Some dog owners are said to resemble their pets, but research shows that dogs and owners who share the same chemical exposures may also share the same diseases.
Man’s best (research) friend
The close relationship humans share with dogs makes our canine companions valuable sentinels to monitor the effects of chemicals on human health.
From a research perspective, in addition to sharing the same environment and chemical exposures as humans, dogs respond to toxic exposures in similar ways to humans. Dogs age seven or more times faster than humans. Their shorter life spans and compressed latency periods for developing disease make them ideal research subjects from a physiological perspective. And while dogs share many of the same diseases as humans, they don’t indulge in lifestyle behaviours such as smoking and drinking alcohol, which can affect study results.
Dogs stand in for kids
Like our pets, children are more sensitive to chemicals than adults. As children grow and their organ systems develop, the ingestion of chemicals can interfere with normal development. When children ingest chemicals, in food, for example, they take in a proportionally larger amount of chemicals than adults, due to children’s lower body weight.
And children share other characteristics with our canine companions. Both crawl around and play on grass and floors. Children put their fingers in their mouths, while dogs lick their paws and the ground, ingesting chemicals in household dust.
How sick is that doggy in the window?
Like caged canaries’ sensitivity to dangerous levels of carbon monoxide in mines, dogs are more sensitive to environmental contaminants than humans. Studies have documented the toxic effects of chemical substances on dogs for decades, raising red flags about human health concerns.
In the 1980s, dogs alerted researchers to the dangers of asbestos. When dog owners who worked with asbestos brought asbestos fibres home on their work clothes, exposed dogs began developing mesothelioma (a lung disease) at eight times the normal rate. Chrysotile asbestos particles were also found in dogs’ lungs.
Affected dogs tended to live in urban surroundings and were often also exposed to flea repellant, a product containing asbestos-like fibres. Asbestos fibre in home insulation is also a significant health risk for dogs and humans.
A large 1981 study of 8760 dogs at 13 veterinary teaching hospitals in Canada and the US found that dogs that lived in industrial areas were more likely to die of bladder cancer. Carcinogens from industrial operations were suspected as a key factor for the development of this type of cancer. When human deaths from bladder cancer were studied in these areas, they too showed a similar correlation with industrial activity.
Dogs have played an important role in studies on the effect of air pollution since a study in London, England, in the late 1930s revealed an increased risk of cancer of the tonsils in city dogs, a finding which was replicated in Philadelphia in the 1960s. Dogs living in Boston and Philadelphia were also found to have higher rates of chronic pulmonary disease than those that lived in suburban areas.
And more recently in 2008, researchers in Mexico City undertook groundbreaking studies of the effects of air pollution on dogs and children. Brain MRIs performed on the children revealed that 56 per cent had prefrontal white matter hyperintense lesions—and so did 57 per cent of the small sample of dogs that were tested. Researchers surmised that the inflammation observed in the children’s brains as a result of damage from air pollution contributed to cognitive problems in otherwise healthy children.
Pesticides and herbicides
A 2012 study that examined the application of lawn care products found that dogs that were exposed to professionally applied lawn care products had a 70 per cent increased risk of developing canine malignant lymphoma. This type of lymphoma in dogs is used as a model for non-Hodgkin’s lymphoma in humans.
Chemicals in lawn care products have also been linked to bladder cancer in dogs in several influential studies over the past 25 years.
Veterinary researcher Lawrence Glickman, along with other researchers, discovered that Scottish terriers (Scotties) are 20 times more likely to develop transitional cell carcinoma (a common form of bladder cancer) than other dog breeds. He also found that Scotties that were exposed to lawn herbicides were four to seven times more likely to develop bladder cancer. Identifying a gene in Scotties that is responsible for this heightened chemical sensitivity could hold promise for identifying a similar gene in humans.
Researchers believe that a chemical called 2,4-D, a phenoxy herbicide, increases the risk of bladder cancer, although inert chemicals in lawn herbicides could also play a role.
In one study, Glickman’s research team looked at the effect of diet on cancer prevention. Scotties that ate leafy green or yellow-orange vegetables at least three times a week had a 70 to 90 per cent reduced risk of developing bladder cancer.
Dogs also come into contact with pesticides through the direct application of flea repellants, shampoos, collars and other products designed to protect dogs from fleas and ticks. But the health effects can be serious—not only for dogs but also for pet owners and their children.
Toddlers may be especially vulnerable. They come into contact with these pesticides when petting a dog, touching pet toys, crawling on rugs and floors and touching dust on floors, then putting their hands in their mouths. Pregnant women should also avoid handling these products.
But these products are most harmful to pets, according to the US group Natural Resources Defense Council (NRDC). While data is scarce, the NRDC claims that hundreds, and possibly thousands, of pets have become sick or have died from pesticide exposure in flea and tick products. (See sidebar on page 55 for safer options.)
Like humans exposed to tobacco smoke, dogs are also susceptible to the negative health effects of second-hand smoke. Long-nosed breeds, such as collies, are at higher risk of developing nasal tumours than short- or medium-nosed breeds due to carcinogens collecting in their nasal passages. Although they rarely develop lung cancer, dogs who develop nasal tumours seldom survive more than one year after diagnosis.
Short- and medium-nosed dog breeds have higher rates of lung cancer because their shorter noses don’t trap carcinogens found in second-hand smoke, allowing the inhaled smoke to travel to their lungs.
Not only dogs, but also cats, birds and any other pets we share our homes and environment with are exposed to the same chemicals we come into contact with every day. If these chemicals have been making our pets sick for so long, it’s sobering to consider the health risks they pose to us and our families—especially our children.
Control fleas safely
- Avoid commercial flea and tick products.
- Comb your dog regularly. Drown any fleas that are combed out in soapy water.
- Bath your dog in soapy water regularly (again, don’t use harsh commercial products).
- Wash your pet’s bedding in hot water once a week.
- Vacuum regularly and throw out the bag after vacuuming.
- When all else fails, ask your veterinarian about the safest products to use. >
What about cats?
Although this article focuses on dogs, cats are also vulnerable to the same toxic chemicals that dogs are. Cats may be even more susceptible to toxins, as they spend much time grooming.
Second-hand smoke is particularly deadly to cats. Need an incentive to quit smoking? Breathing in second-hand smoke puts cats at a greater risk of developing
- cancers of the lymph nodes (malignant lymphoma) and mouth
- lung disease
- eye irritation
- wheezing and coughing
- lethargy and depression
Teflon isn’t for the birds
When Teflon-coated pans are heated at high temperatures, they produce polytetrafluoroethylene (PTFE) fumes. When birds breathe in these fumes, they develop Teflon toxicosis. Their lungs hemorrhage and fill with fluid, causing birds to suffocate.
Studies have shown that humans also carry these chemicals in our blood. Some newer non-stick products that don’t contain PTFE claim to be environmentally friendly, but Teflon is still widely used as a non-stick coating. Some safer cookware options are
- cast iron or porcelain enamelled cast iron
- stainless steel
Keep pets safe
Pet proof your home to avoid exposing your pet to these common toxins:
- human, over-the-counter and veterinary medications
- pesticides, herbicides and garden products
- automotive products, including antifreeze
- household cleaners, bleach, paints and solvents
- chocolate (can cause vomiting, diarrhoea, high heart rate and seizures)
- xylitol, a sugar substitute (can cause seizures and liver failure in dogs)
- second-hand smoke and cigarette and tobacco products