Expert discusses fluoridated water and horses

The mineral fluorite, a common mineral and chief source of fluoride for commercial applications
The mineral fluorite, a common mineral and chief source of fluoride for commercial applications. © Ryan Salsbury

There is no reliable evidence to show that any horses have ever suffered flouride poisoning through drinking fluoridated public water, a veterinary clinical toxicologist says.

Associate Professor Cynthia Gaskill, toxicology section chief at the Veterinary Diagnositc Laboratory at the University of Kentucky, said the potential risk of fluoride-supplemented public water to horses was a topic that periodically arose.

“A casual internet search of this topic can uncover alarming reports purporting fluoride poisoning in horses from fluoridated municipal water,” Gaskill noted in the latest issue of Gluck Equine Disease Quarterly.

“These reports typically are published in non-peer reviewed sources and are missing important information necessary to confirm the diagnosis, to rule out exposure to other fluoride sources, and to eliminate other potential causes.

“A careful review of the peer-reviewed literature in reputable scientific journals showed no published reports documenting fluoride poisoning in horses due to ingestion of fluoridated public water.”

Fluoride, she said, was one of the most common elements in the environment and was found naturally in soil, rock, water, air, plants, and animal tissues.

“Volcanic rock and ash and water from deep wells or hot springs in some regions are naturally high in fluoride. Low concentrations of dietary fluoride can be beneficial to animals; excessive amounts can cause fluoride poisoning (fluorosis).

“Fluorosis can occur in any species, including horses.

“In the past, fluorosis occurred more commonly due to ingestion of forages or waters contaminated with fluoride-containing industrial waste, high-fluorine rock-phosphate supplements in animal feeds, and fluoride-containing rodenticides, insecticides, and other chemicals,” she said.

Cynthia Caskill
Cynthia Caskill

“Regulations restricting the amount of fluoride in industrial pollution, requiring de-fluoridation of rock-phosphate feed ingredients, and banning many fluoride-containing pesticides have greatly decreased the occurrence of fluorosis.

“Fluoride poisoning still occasionally occurs in areas with high volcanic activity or secondary to ingestion of fluoride-containing medications or contaminated water.

“Acute, high-dose intoxications result in severe signs and rapid death. Chronic, lower dose intoxication causes predominantly tooth and bones abnormalities,” Gaskill said.

“While small amounts of fluoride improve tooth and bone strength, excessive amounts can cause lameness, stiffness, bone thickening, pain and difficulty eating, weight loss, poor growth rates, and poor health.

“Teeth are affected during the period of tooth development, which in horses is complete before 4 to 5 years of age. Fluorotic dental lesions will not develop if animals are exposed to excessive fluoride after permanent teeth have erupted.”

Gaskill noted that public water sources were supplemented in some areas with fluoride to help prevent dental disease in humans.

“Fluoride supplementation in public water is targeted to achieve fluoride concentrations of 0.8 to 1.3 milligrams per litre. The maximum fluoride concentration permitted in public water sources by the [US] national Safe Drinking Water Act is 4 milligrams per litre.”

Gaskill noted that the maximum safe level of fluoride in water for horses had not been established.

“Published guidelines for horses are based on extrapolations from other species. In the USA, the Environmental Protection Agency recommends a maximum fluoride concentration of 2 milligrams per litre in water intended for livestock.”

She noted that in Kentucky, most horses drank fluoridated public water as their major water source, and fluorosis was not seen in this horse population.

“Studies are needed to determine safe limits of fluoride in feed and water for horses. However, evidence to date indicates that fluoride concentrations allowable in US public water systems are well tolerated by horses and do not cause fluorosis.”


Gluck’s Equine Disease Quarterly is funded by underwriters at Lloyd’s, London, brokers and their Kentucky agents.

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4 thoughts on “Expert discusses fluoridated water and horses

  • October 14, 2012 at 3:48 am

    Meet Cathy and Wayne Justus of Pagosa Springs, Colorado who experienced incredible debilitating symptoms in their world class quarter horses and their dogs with seemingly no source or reason. After the death of Cathy’s prize horse, the local veterinarian tested for every known possibility for the cause but could not come up with an explanation. It was not until Dr. Lennart Krook, Professor Emeritus of Cornell University College of Veterinary Medicine, tested for fluoride toxicity that they knew for certain what was killing their horses. They had been poisoned by fluoride in their drinking water. Quote from Justus, “I have the sad distinction of owning the first horses to ever be diagnosed with chronic fluoride poisoning from artificially fluoridated municipal water. I have this distinction, not because it hasn’t been happening for years all over this world, but because vets, like doctors and dentists, are not taught in their schooling the science and biochemistry of fluoride and what it does to the body. I know of this lack of training of proven science because I have made it a point, over the last 25 years, to talk to hundreds of these professionals. We have now lost 8 horses and 4 dogs to this virulent cumulative toxin. This was scientifically proven by the world’s authority of fluoride poisoning at Cornell University in New York.”

    You can view Cathy Justus’ very personal story with pictures of her champion quarter horses, studies, and related videos at her personal MySpace

    An excellent documentary of the Justus’ heartbreaking story can be seen on YouTube.
    Direct access to the well-documented, published, peer reviewed studies about her horses by Krook/Justus and prefaced by an editorial by Dr. Albert Burgstahler This manuscript led to a second peer-reviewed manuscript on fluoride poisoning of her horses by Justus/Krook. Do you think that this has not happened to others? Here is another peer-reviewed manuscript on horses in Texas by Krook/Macicek.

  • October 14, 2012 at 4:11 am

    Horse owners should watch the video themselves and make their own decisions. It brought artificial water fluoridation to an end in their area of Colorado. Fluoride poisoning was confirmed through lab analysis.

    Poisoned Horses

    The signs of fluorosis from chronic ingestion are the same regardless of the source of fluoride. Levels too low to produce skeletal signs can cause changes in the enamel of developing teeth, leading to chalkiness or mottling, staining, and rapid and irregular wear. When exposure occurs after dental development, the teeth remain normal even if severe skeletal fluorosis develops. Clinical signs, apart from mild tooth lesions, occur in many animals when bone fluoride reaches 4,000 ppm. Skeletal fluorosis results in accelerated bone resorption and remodeling with production of exostoses and sclerosis. Metabolically active bones (ribs, mandible, and long bones) and growing bones in the young are most affected. Affected animals are lame, and feed and water intake and weight gain are decreased. Severely diseased cattle may move around on their knees due to spurring and bridging of the joints in the late stages. When the skeleton becomes saturated (30-40 times normal bone content), “flooding” of the soft tissue occurs, which causes a rise in plasma fluorides and metabolic breakdown evidenced by a loss of appetite and listlessness

    Merck Vet Manuel

  • October 18, 2012 at 2:45 pm

    I see that the writer of this article claims that internet activity shows the dangers of fluoride but none have provided unequivocal proof of the dangers.. I ask then how it is that the writer can claimj that horses who are exposed to low doses of fluoride have stronger and healthier teeth.. DO YOU HAVE ANY PROOF OF THIS CLAIM THAT THE HORSES TEETH ARE BETTER WITH FLUORIDE.. The asnswer will always be NO because that is the same claims that fluoride proponents for humans make but have never provided unequivocal proof..

  • July 30, 2018 at 2:38 pm

    Your comments and concerns are well understood Victor Heslop. But the above author may not have been properly introduced to the subject of horses getting sick from fluoride. You may notice the Justus horses in the DVD getting the same lameness, skin disease and the asthmatic coughing I see with people in my practice ever since my city was fluoridated 9 years ago. When testing is done, it has been the fluoridated water triggering the asthmatic coughing. Horses get the similar toxicity signs as people.


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