The dogs of war

The study of dogs that served - and died - serving in Vietnam provides important information on toxic chemicals that can help direct health policy in the United States

by Peter Montague, reprinted from Rachel's Environment & Health Weekly, #436, April 6, 1995
omewhere between 2.6 and 3.8 million American men and women served in Vietnam during the years 1965 through 1971, the years when chemical herbicides were being used to denude the jungle and destroy enemy crops. Military records do not allow a more accurate determination of the true number who served.
Alongside the humans serving in Vietnam, there were 3,895 military working dogs, almost all of them purebred German shepherds. These dogs served as scouts, sentries, trackers, mine detectors, and tunnel explorers. About 91% of these dogs were "intact" (uncastrated) males.
When a military working dog dies, regardless of the circumstances of death or the duty location, an autopsy is performed by a veterinarian, and a standardized set of tissue specimens and organs are sent to the Armed Forces Institute of Pathology in Washington, D.C.
During the late 1980s, researchers compared autopsy records of 1,167 military working dogs with Vietnam service with autopsy records of 791 military working dogs who served in the continental United States and saw no Vietnam service. In a separate study, the stateside dogs were also compared to 437 dogs that died in Okinawa, because many dogs that served in Vietnam were sent to Okinawa after the war.
These studies showed that dogs who served in Vietnam were about 1.8 times as likely to have cancer of the testicles, compared to military working dogs who served only in the states. Similarly, military dogs that died in Okinawa were about 2.2 times as likely to have testicular cancer as dogs who served only in the states. A separate study was then conducted, excluding the dogs who had testicular cancer. Among the non-cancer dogs, there was clear evidence of significant deterioration of the testicles in those dogs who served in Vietnam: degeneration of the testicles, atrophy of the testicles, and evidence of a below-normal ability to produce sperm.

Medical models

Dogs have often served as sentinels of human disease. In 1938, well-known researcher W.C. Hueper showed that beta-naphthylamine caused bladder cancer in dogs. In 1954, researchers showed that another industrial chemical, 4-aminodiphenyl, produced bladder cancer in dogs. In 1980, a study of 8,760 pet dogs showed that bladder cancer in dogs correlated with residence in industrialized counties in the United States and Canada; this same study showed that bladder cancer in men and women was similarly correlated with residence in industrialized areas. "The findings of this study suggest that the bladder cancer experience of pet dogs resembles that of human beings living in the same general locale," the study concluded.
Pet dogs are particularly relevant in such studies. Forty million pet dogs share their owner's domestic environment but don't indulge in behavior that could confuse or confound the interpretation of epidemiological studies: dogs don't smoke, and they usually don't work. In 1983, a study of pet dogs with the asbestos-related lung disease, mesothelioma, showed that their disease correlated with household members who worked in an asbestos-related job, had an asbestos-related hobby or applied flea powder to their dog.
For these reasons, the finding of testicular cancer and testicular dysfunction in dogs who served in Vietnam was an eye-opener. It soon led to a comparison of 271 human veterans with testicular cancer to 259 veterans without testicular cancer, to see whether Vietnam service was related to testicular cancer. This study revealed that, like dogs, human veterans of Vietnam were 2.5 times as likely to have testicular cancer compared to veterans who did not serve in Vietnam.

Seeing orange

What aspects of military service in Vietnam caused testicular cancer in men, and testicular cancer and dysfunction in military working dogs?
An obvious suspect is Agent Orange, 11.2 million gallons of which were sprayed over 3.6 million acres of Vietnam. Agent Orange, named for the orange stripe on its 55-gallon storage containers, is a 50-50 mixture of two herbicides: 2,4,5-T and 2,4-D. One of these, 2,4,5-T, was banned in the United States around 1980 following evidence that it could cause birth defects in humans. The second component, 2,4-D, remains in wide use throughout the United States where it is popular for killing dandelions and other broad-leaf plants in lawns, and as an agricultural weed killer.
During manufacture, the herbicide 2,4,5-T unavoidably becomes contaminated with dioxin. According to the National Academy of Sciences, the average dioxin contamination in Agent Orange in Vietnam was 2 parts per million (ppm). An estimated total of 368 pounds of dioxin was sprayed onto Vietnam's land and people during the seven-year spraying program.
However, a recent study of Vietnam veterans that tried to estimate 2,4,5-T exposure and link it to testicular cancer found that only Navy men had elevated levels of testicular cancer associated with 2,4,5-T exposure; men in the other services showed no such effect of exposure. The authors of that study speculated that Navy men might also have been exposed to fuels (oil and gasoline), which previous studies have linked to testicular cancer.
The other half of Agent Orange, herbicide 2,4-D, is also a suspect. Although the manufacturers of 2,4-D claimed for years that their products were not contaminated with dioxin, this claim has now been shown to be false, using the manufacturers' own data. Dioxin has been shown to damage the reproductive organs and systems of many animal species, including men and women.
A study of pet dogs in the United States found excess cancers associated with 2,4,-D lawn spraying. A study of 32 farmers who sprayed 2,4-D, compared to a control group of 25 unexposed farmers, revealed significant effects on the exposed farmers: diminished sperm count, increased number of sperm with poor motility (swimming ability), increased numbers of dead sperm, and increased numbers of malformed sperm.
No federal agency keeps close track of pesticide use in the United States. However, the Environmental Protection Agency estimates that U.S. farmers apply 25 to 30 million pounds of "active ingredient" of 2,4-D each year. Non-agricultural use of 2,4-D in the United States is estimated at 12 to 15 million pounds of "active ingredient" per year. (The "active ingredient" of a pesticide is only 0.5% to 5% of the total formulation so these "active ingredient" amounts must be multiplied by anywhere from 20 to 200 to get the total volume of 2,4-D formulations used each year. The bulk of the formulations are secret ingredients called "inerts" which are, themselves, often toxic solvents.)
Other chemicals suspected of causing testicular cancer and dysfunction in dogs and humans who served in Vietnam are the antibiotic tetracycline and the pesticide malathion. Many military dogs in Vietnam suffered from ear infections and other diseases, and received one or more doses of tetracycline during their tour of duty. Tetracycline is strongly absorbed by sperm in mammals, and is known to cause testicular atrophy, and diminished sperm quality in humans and dogs.
The other suspicious candidate is malathion. The same military units that sprayed Agent Orange also sprayed DDT and malathion extensively in the vicinity of U.S. troops to reduce the dangers of malaria carried by mosquitoes. It has been reported that 44 percent of the land of southeast Asia, mainly Vietnam, was sprayed with malathion during the war. Furthermore, military working dogs in Vietnam were dipped in a 0.5 percent solution of malathion to kill disease-carrying ticks. Malathion is known to cause testicular atrophy and damage to the sperm-generating cells of laboratory animals.
Malathion is currently widely used throughout the United States for mosquito control - though not for fear of malaria. Mosquitoes are simply a nuisance. EPA estimates that 4 to 6 million pounds of "active ingredient" of malathion are sprayed in the United States each year. The annual total of malathion formulations sprayed is, again, 20 to 200 times this amount.

Count down

Sperm count in men throughout the industrialized world appears to be dropping. Testicular cancer is the most prevalent cancer among white males between the ages of 25 and 34 years and the second most common in the 35-to-39 age group. The causes of testicular cancer are thought to be environmental because the rates vary widely from one location to another. During the past 15 years, the rates have increased rapidly (2.3 to 3.4 percent per year) in many industrialized countries.
It may take scientists many decades to tell us all we would like to know about a complex chemical like dioxin or malathion. However, we already know enough to act. To guide our personal choices and new public policies, to minimize the danger to ourselves, our families, and our communities, we need only to remember that chemicals not used cannot cause harm. This we can learn from the dogs of war.

Rachel's Environment & Health Weekly is published by Environmental Research Foundation, providing information on toxic substances, their impact on human health and communities, the corporations and technologies that produce them, and alternatives. The newsletter covers many technical issues written in plain language that anyone can understand. For subscription information, contact the Foundation at P.O. Box 5036, Annapolis, MD 21403; Fax (410) 263-8944; Internet: