Walking On Volume 7, Issue 2, February 2020 | Page 8
For the Health of It
Fluoridated Water and Horses
Reprinted with permission from Equine Disease Quarterly, Volume 21, Number 4
The potential risk of fluoride-supplemented public
water to horses is a topic that periodically arises. A casual
internet search of this topic can uncover alarming reports
purporting fluoride poisoning in horses from fluoridated
municipal water. 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-re-
viewed literature in reputable scientific journals showed
no published reports documenting fluoride poisoning in
horses due to ingestion of fluoridated public water.
Fluoride is one of the most common elements in the
environment and is 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 hors-
es. 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 flu-
oride-containing rodenticides, insecticides, and other
chemicals. Regulations restricting the amount of fluo-
ride in industrial pollution, requiring de-fluoridation
8 • Walking On
of rock-phosphate feed ingredients, and banning many
fluoride-containing pesticides have greatly decreased the
occurrence of fluorosis. Fluoride poisoning still occasion-
ally occurs in areas with high volcanic activity or second-
ary 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. 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 4-5 years of age. Fluorotic dental le-
sions will not develop if animals are exposed to excessive
fluoride after permanent teeth have erupted.
Public water sources in Kentucky and nationwide of-
ten are supplemented 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 mg/L. The maximum fluoride concentration
permitted in public water sources by the national Safe
Drinking Water Act is 4 mg/L. The maximum safe level
of fluoride in water for horses has not been established.
Published guidelines for horses are based on extrapola-
tions from other species. In the USA, the EPA recom-
mends a maximum fluoride concentra- tion of 2 mg/L in
water intended for livestock.
In Kentucky, the majority of horses drink fluoridated
public water as their major water source, and fluorosis
is 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 U.S. public water systems are
well tolerated by horses and do not cause fluorosis.
CONTACT:
Dr. Cynthia Gaskill
(859) 257-8283, [email protected]
Veterinary Diagnostic Laboratory
University of Kentucky, Lexington, Kentucky