By Peter Montague
Somewhere between 2.6 and 3.8 million US 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.
Alongside the humans serving in Vietnam, there were 3895 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 standardised set of tissue specimens and organs are sent to the Armed Forces Institute of Pathology in Washington, DC.
During the late 1980s, researchers compared autopsy records of 1167 military working dogs with Vietnam service against autopsy records of 791 military working dogs who served in the continental US 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 which served in Vietnam were 1.8 times as likely to have cancer of the testicles, compared to military working dogs who served only in the States. Likewise, military dogs that died in Okinawa were about twice as likely (2.2 times as likely) to have testicular cancer as dogs which served only in the States.
A separate study was then conducted, excluding the dogs which had testicular cancer. Among the non-cancer dogs, there was clear evidence of significant deterioration of the testicles in those dogs which served in Vietnam (compared to dogs which served only in the US): degeneration of the testicles, atrophy (shrinking) of the testicles and evidence of a below-normal ability to produce sperm.
Dogs have often served as sentinels of human disease. Back in 1938, the 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 8760 pet dogs showed that bladder cancer in dogs correlated with residence in industrialised counties in the US and Canada; this same study showed that bladder cancer in men and women was similarly correlated with residence in industrialised 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 because 40 million pet dogs share their owner's domestic environment yet do not indulge in behaviour that could confuse or confound the interpretation of epidemiologic 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 (a) worked in an asbestos-related job, or (b) had an asbestos-related hobby or (c) applied flea powder to their dog.
For these reasons, the finding of testicular cancer and testicular dysfunction in dogs that served in Vietnam was an eye-opener, and 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 about twice as likely (2.5 times as likely), to have testicular cancer compared to veterans who did not serve in Vietnam.
Naturally, the question occurs: 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, which was sprayed in large quantities (42.4 million litres) over 1.5 million hectares of Vietnam. Agent Orange, named for the orange stripe on its 55-gallon storage containers, was 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 US about 1980 because evidence indicated that it could cause birth defects in humans; 2,4-D remains in wide use throughout the US, where it is popular for killing dandelions and other broad-leaf plants in lawns, and as an agricultural weed killer.
During manufacture, 2,4,5-T becomes contaminated with dioxin unavoidably. 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 167 kg of dioxin was sprayed onto Vietnam's land and people during the seven-year spray 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 to 2,4,5-T. The authors of that study speculated that Navy men might also have been exposed to fuels which previous studies have linked to testicular cancer.
The other half of Agent Orange, 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 (US Environmental Protection Agency draft review, 1994).
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 US found excess cancers (lymphomas) associated with 2,4-D lawn spraying. And 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; increased numbers of dead sperm; and increased numbers of malformed sperm.
No federal agency keeps close track of pesticide use in the US; however, the US Environmental Protection Agency (EPA) estimates that farmers apply 11.3 to 13.6 million kilograms of "active ingredient" of 2,4-D each year in the US. Non-agricultural use of 2,4-D in the US is estimated to total another 5.4 to 6.8 million kilograms 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 2,4-D formulation used each year. The bulk of the formulation is 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. Therefore, many received one or more doses of tetracycline. 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 unit that sprayed Agent Orange also sprayed DDT and malathion extensively in the vicinity of US troops, to reduce the dangers of malaria carried by mosquitoes. It has been reported that 44% of the land of south-east Asia, mainly Vietnam, was sprayed with malathion during the war. Furthermore, military working dogs in Vietnam were dipped in a 0.5% solution of malathion to kill ticks. Malathion is known to cause testicular atrophy and damage to the sperm-generating cells of laboratory animals.
Malathion is widely use throughout the US today for mosquito control. EPA estimates that 1.8 to 2.7 million kilograms of "active ingredient" of malathion are sprayed in the US each year. The yearly total of malathion formulation sprayed is, again, 20 to 200 times this amount.
Sperm count in men throughout the industrialised 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 last 15 years, the rates have increased rapidly (2.3% to 3.4% per year) in many industrialised countries.
[From Rachel's Environment & Health Weekly.]