Not every occupational risk that comes with military service results from enemy munitions. We must remain alert to the more insidious threats such as cancer and reproductive damage, and remember our obligation to those who have placed themselves in jeopardy.
Every person wearing a military uniform recognizes that duty during wartime is dangerous. Beyond the threats from enemy munitions, however, there are other perils, often forgotten, whose sinister long-term impact on the health and longevity of military personnel can be substantial.
Enclosed Spaces
Improvements in weapon design and delivery systems often create additional hazards for the personnel who operate within and around them. The American Civil War introduced the rapid-firing predecessor of the machine gun, an innovation that increased substantially a gunner’s exposure to toxic propellant-combustion products. Fearing gas attacks during World War I, machine gunners sequestered themselves within enclosed spaces and attempted to create airtight envelopes around themselves and the breeches of their machine guns. Contamination of their breathing spaces by the dangerous gas carbon monoxide—produced by the incomplete combustion of propellant in the machine gun shells—caused many subsequent casualties. Similarly, health-hazard assessments of new self-contained armored gun systems have outlined many areas of concern: hazardous chemical exposures through inhalation and skin contact within the armored enclosure; temperature extremes; radiation-energy exposure; noise-level extremes; oxygen deficiency; and whole-body vibration.
The operating environment within the Navy has a similar requirement of enclosure within confined spaces. Before World War I, the German Navy experienced problems with “nitrous fumes” filling the confined space within naval gun turrets when the gun breech was opened for reloading. The gunners were overcome by the irritant gas—a mixture of nitric oxide (NO) and nitrogen dioxide (NO2), resulting from the combustion of the propellant—despite their having worn respirators. The gunners often were exposed to high concentrations of NO, which can precipitate methemoglobinemia, a dangerous condition that limits the blood’s capacity to carry oxygen and often leads to death. The protective masks, consistent with the practice of the day, commonly contained soda-lime and activated coconut-shell charcoal. Not only did they evidently not remove NO, they may actually have increased its content within inspired air through the chemical change of N02 to NO. To counteract this, the Germans introduced a compressed-air bore cleaner that evacuated the combustion products in the large gun tubes before the gun breech was opened. To this day, however, the presence of NO and N02 in such enclosed spaces remains a matter of serious concern.
Before the nuclear age, the internal environment of the submarine was similarly unpleasant. Undersea craft initially were required to surface frequently to recharge their batteries, but in the 1930s, Dutch naval experts developed the snorkel, which allowed these craft to remain submerged for long periods (one German U-boat remained submerged for 69 days). When needed, a fan pulled in fresh air, and the diesel engines were run under the sea. Submariners, however, described foul, stale air that reeked of unpleasant odors such as diesel fuel and mildew, that covered food, clothes, and bunks.
Within the U.S. Navy during World War II, there were many incidents of reduced effectiveness in submarine crews because of “defective habitability.” Navy reports cited examples such as: “Battery compartment flooded during torpedo attack, emitting chlorine gas into the boat”; “Lack of air conditioning decidedly had a debilitating effect on crew, and slowed their reactions”; “Patrol somewhat handicapped by poisoning (carbon tetrachloride) which affected majority of crew over a ten-day period” (carbon tetrachloride was used to clean electric motors; when the motors became hot, it volatilized and produced the dangerous gas phosgene).
The debut of the nuclear submarine in 1955 brought with it atmospheric control—oxygen is extracted from sea water and air scrubbers remove contaminants—but concerns about air quality persist because submarines still carry many high-energy batteries, and their charging liberates hydrogen and oxygen. In this atmosphere, electrical panel fires can be very difficult to extinguish. Additional fire risks from cigarettes, deep fat fryers, oxygen generators, the catalytic convertor, and laundry dryers still make this a hazardous environment. Similarly, the trend in ventilation design on board some newly designed surface ships has been toward self-contained “closed loop” systems. This aligns these surface ships’ fire and ventilation problems with those of submarines, including greater concern over toxic gas dissemination within the ships’ enclosed spaces.
In recent years, advanced materials (graphite composites, synthetic lubricants, artificial fibers and fabrics, adhesives, matrix systems, and advanced coatings) have played increasingly important roles in military designs. Unfortunately, many of these materials also possess significant thermal and flammability properties, as well as the propensity to form a multitude of inhalable toxic byproducts upon incineration.
Furthermore, fire-effect studies on the integrity of bulkheads separating ship compartments have demonstrated the easy propagation of smoke, as well as these particulate byproducts of combustion, through the various conduit systems and wire bundles that penetrate these barriers. The potential short- and long-term impact on crew members during fire suppression and damage control may be substantial.
The Persian Gulf War
Following the conclusion of Operations Desert Shield and Desert Storm, a National Institutes of Health workshop concluded that the biological, chemical, physical, and psychological complexities of the Persian Gulf environment appear to have had complex health results for primary-level military personnel. Indeed, research has shown that U.S. troops were exposed before, during, and after the Persian Gulf War to a variety of potentially hazardous substances.
The Inhalation Threat. Long-term exposure to high concentrations of airborne inorganic dusts can result in a form of lung disease called pneumoconiosis, which affects the lungs’ ability to exchange oxygen for the waste gases of body metabolism. Only individuals who are chronically exposed to high concentrations of inorganic dusts are susceptible to the disease, but the specific length of exposure necessary to declare risk is unknown.
Saudi Arabia and Kuwait have the highest atmospheric particle count in the world. Depending on atmospheric conditions, it can exceed the “significant harm” levels of air quality, as defined by U.S. Environmental Protection Agency standards. Within the Gulf War environment, the sand, bacteria, heavy metals (including depleted uranium), and possibly low levels of chemical/biological agents may have acted in various combinations to further burden the usual atmospheric aerosols in the area. Exposure of U.S. troops to these multiple agents certainly could have resulted in independent or additive effects and created various inhalation diseases. (Indeed, at one Army station hospital, the prevalence of respiratory disease was 43% of sick call, and involved 7% of the total personnel.)
Sand and Other Airborne Particles. In southwest Asia, the sand is very loose, and microscopic sand particles (mixed clays, silicon-rich and calcium-rich mineral types) easily can be carried by the vigorous Shamaal winds of the region. Chronic exposure to the blowing sand causes Desert Lung Syndrome (silicate pneumoconiosis), a disease well known to the Bedouin nomads. During 1982, the measurable yearly average of suspended dust particles (small enough to be breathed) in Saudi Arabia was found to be more than ten times higher than those recorded in Europe and the United States. These levels can result in acutely incapacitating breathing difficulty, usually compromise the heart and lung status of vulnerable subjects, and may cause premature death. The heavy traffic of military vehicles, the digging of bunkers, and explosions during the Gulf War further disrupted the upper crust of the desert and increased the concentration of fine sand and other particles in the air.
During the war the dust was even responsible for premature engine failure in some Black Hawk helicopters. Fine particles were able to bypass filters and enter the cooling and combustion systems, where the sand reacted with the hot combustion gases and led to the deposit of calcium silicate, glass, and various crystalline silicates on the turbine vanes.
Foreign particles and infectious agents also usually are found in sand/soil and may provoke disease when inhaled. Cultures of sand from the Persian Gulf have yielded many varieties of bacteria, fungi, and yeasts. During the Gulf War, airborne-particle analysis revealed the presence of various allergy producing fungus spores and pollen grains in concentrations exceeding their threshold level, even in the dry climate of Saudi Arabia. Military personnel stationed in previously abandoned villages in Jeddah, A1 Khobar, and Riyadh were further exposed to large deposits of pigeon droppings, which in some cases triggered allergic lung conditions similar to asthma.
Pollution from Hydrocarbons. As they retreated from Kuwait, the Iraqis systematically ignited oil wells. At the end of July 1991, approximately 400 of the original 613 wells ignited were still burning. Before the last fire was extinguished on 5 November 1991, approximately 900 million barrels of oil had been either burned or spilled. The fires produced large quantities of smoke, soot particles, and other chemical pollutants—including trace metals, carbon dioxide, hydrogen sulfide, and sulfur dioxide— making the air a cause of genuine concern to U.S. military personnel still stationed there.
During the Gulf War, hydrocarbon emissions in the atmosphere also were created by ever-present electric generators, as well as by fixed and rotary wing aircraft, which burned a kerosene-like fuel. Additional pollution was supplied by the internal combustion engines within thousands of diesel-fueled trucks and tracked vehicles. Diesel fuel also was “irrigated” along well-traveled routes to form a crust in the upper layers of the sand to prevent the roads from blowing away.
Diesel exhaust particle exposure has been associated with allergic conditions of the nasal passages and with asthma. It can cause an initially reversible decrease in lung functions and can increase the lung’s absorbability, allowing entry of allergic substances into the linings of the breathing passageways. Protracted contact also may facilitate the development of cancer.
Heavy Metals. Among U.S. casualties, nine showed “extraordinarily high” chromium levels. The source was believed to be inhalable airborne particulates from the soil and sand of the Gulf, analysis of which has shown variable amounts of chromium. One air particulate study showed a sharp increase in chromium between March and July 1991. Inhaled chromium has been associated with cancer of the lung, nose, and paranasal sinuses, and research has suggested the potential role of small amounts of chromium in the development of lung cancer, especially when aggravated by factors such as tobacco smoking. The levels of chromium particles in the Persian Gulf may not have been “abnormally” high, but their cancer-stimulating effects and potentially adverse impact on genes might have been magnified by the presence of silica, bacteria, and/or fungi in the air. This theoretical risk, however, remains unproved.
Depleted Uranium. Gulf War operations marked the first use of depleted uranium shells in combat. Thousands of armor-piercing rounds of depleted uranium were fired by antitank cannons, the A-10, and a number of gatling-type guns. (The Abrams tank contains depleted uranium in portions of its armor and ammunition as well). The kinetic energy from the impact of such shells causes their aluminum covering to be tom away and the uranium metal within to be incinerated. The resulting vaporized aerosol of uranium oxide is readily swallowed or inhaled and generally presents a greater risk to exposed individuals than low-level nuclear toxicity.
Uranium also may represent a significant health risk when inhaled in large concentrations. Long-term inhalation of uranium dust can cause irreparable damage to the kidneys and has been implicated as another active agent in the development of lung cancer among uranium-ore miners. Miners who smoke are at a proportionately higher risk. The adverse health effects of uranium when combined with chromium, sand, and other acknowledged toxic agents are worrisome but unknown.
Chemical and Biological Agents. Iraq certainly had the capacity and intent to use chemical and biological armaments against Coalition forces. Long capable of producing mustard gas. Sarin, nerve agent VX, hydrogen cyanide, cyanogen chloride, Lewisite, and multiple other chemical weapons, by the start of the Gulf War it also had developed chemical-delivery capabilities for rifle grenades, mortars, artillery rounds, air-to-ground rockets. Scud warheads, and land mines.
Iraq already had violated the Geneva Convention and the Biological Warfare Convention by using nonnuclear weapons of mass destruction during its war with Iran. Iranian soldiers were exposed to the toxic chemical myco- toxin. Mycotoxin originally was reported as the cause of many cases of blood disorder in the Russian grain belt from the early 1900s until the mid 1950s. All branches of Russian science were mobilized to study the disease. The responsible organism, Trichothecene mycotoxin, was cultured and made available to Iraq, which used it at the initiation of the Kheibar offensive in 1984. Explosions of air canisters were followed by a “yellow rain,” with signs of skin burns, eye damage, and difficulty breathing among victims.
Among the most potent chemical weapons are the organophosphorus nerve gases, which poison the junction points in transmission of nerve impulses. Acute exposure causes visual disturbance, nausea, vomiting, and difficulty breathing. The effects also may be prolonged and cumulative. Chronic exposure in humans and experimental animals causes permanent nerve damage. Psychiatric sequelae may include schizophrenia and depressive reactions, with severe impairment of memory and difficulty in concentration. (Some of these same organophosphate compounds also were used in lower concentrations by our forces as pesticides to control the scorpions and flies around the tents of military personnel. The pesticides used in the Gulf War were commercially available products that had undergone FDA safety and efficacy studies. Most would appear to have been applied below the toxicity levels recognized for commercially available products, although the concentrations of exposure to these pesticides in the war zone are unknown.)
Mustard agents, another chemical weapon, can damage the reproductive elements of cells, namely genetic DNA, thus making it a potential reproductive toxin. There have been no studies examining the effects of prolonged exposure (lasting several weeks) to very low levels of chemical and biological agents, however, which some have argued may have occurred in the Gulf War. Two teams working independently, one Czech and the other French, detected chemical agents during the Gulf War, but DoD has disputed strenuously such arguments regarding exposure to chemical and biological agents through either offensive use by Iraq or fallout from bombed chemical facilities.
Genetic Threats and Cancer Risk
It has been suggested that long-term heavy exposure to a combination of toxic substances similar to those present in the Persian Gulf war theater could weaken the ability of an exposed person’s immune system to fight against the various hazards of both reproductive dysfunction and cancer. Certain toxicants potentially harmful to both male and female reproductive cells certainly were present in the Gulf during the deployment of U.S. troops. Exposures to some of these toxicants may have been widespread, but were of unknown intensity. On the list of such reproductive toxicants, for example, were metal compounds from the oil-well fires (cadmium, lead, mercury, and nickel). Many pesticides and decontaminating agents used in theater also are known reproductive toxicants. Ethylene glycol monomethyl ether, a main component of the decontaminating agent DS2 used extensively during the Gulf War, may cause central nervous system depression and liver damage. In addition, experience in animal models suggests that exposure may have reproductive effects, leading to physical defects in offspring.
DEET and permethrin were the major pesticides used by personnel in the Persian Gulf. Unfortunately, the concentrations of these substances that may cause adverse reproductive outcomes in humans, or even what concentrations existed in the Gulf, are unknown. Some work on combined exposure to both DEET and pyridostigmine, however, has suggested a tenfold increase in the toxicity of the DEET compound.
If people are inadvertently exposed to some cancer-producing agent, it may be many years before the first cancers awaken us to the danger. By then, of course, it may be too late to prevent the wave of cancer cases that is about to come. (In Great Britain, production of the potent bladder carcinogen beta-naphthylamine ceased in 1957, but cases of bladder cancer in the industrial workers who produced it were still occurring 20 years later.)
Since it is now well established that the interaction of multiple environmental factors may increase the incidence of some human cancers more than exposure to a single carcinogen, what can be said about the long-term effects on host defense mechanisms from agents used in the Gulf War? Some studies have demonstrated marked effects on the immune system from exposure to the pesticides used by the military: carbaryl, dichlorvos, lindane, and malathion. What of the long-term effects of exposure to varying combinations of dusts, molds, uranium oxide, chromium, the byproducts of the combustion of petroleum, low doses of chemical warfare agents, or direct exposure to diesel fuel and its fumes? No easy answers are forthcoming.
Other Battlefields: The Ultimate Reality
What other hazards await those in military service apart from the risk of adversarial munitions? Between 1989 and 1992, 700 U.S. uniformed military personnel lost their lives in accidents while engaged in training activities such as swimming, parachuting, weapons training, and physical fitness exercises. What of the more insidious longer- term risks such as lung disease, allergies, reproductive damage, or cancer? Unfortunately, there are no definitive answers. The occupational risks of military service are many, and the implications of such hazardous activity may only become known many years following a service member’s departure from active duty.
Indeed, there are many battlefields for the soldier far beyond the muzzle of an enemy’s weapon. Our alertness to these dangers must be sustained. We must not forget our obligation to those who have placed themselves in jeopardy.
Captain Smith is an actively drilling reservist at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, where he holds appointments as Clinical Professor of Surgery and Clinical Professor of Military and Emergency Medicine. He is on the faculty of the Medical College of Georgia in Augusta, where he serves as Professor of Surgery (Urology).