Particulate matter is a generic term applied to a broad class of chemically, physically, and biologically diverse substances spanning a range of particle sizes. Typically, airborne particulate matter ranges in size from molecular clusters of less than 0.001 microns (m m) to particles more than 50 m m in diameter. A 10 m m particle is roughly one-sixth the width of a human hair. These particles are composed of chemically diverse materials, and are transported in the air as solid particles or liquid droplets.
Particle size analyses conducted on air samples taken in 1991 at several locations in Kuwait and Saudi Arabia (see Section III) indicated that there was a significant mass of particles in the respirable size range (i.e., less than 10m m in aerodynamic equivalent diameter). Particles in this size range (commonly referred to as PM10 see the glossary) have the potential for entering the thoracic region (see the glossary) of the respiratory tract and will deposit either in the tracheobronchial region (conducting airways of the lung) or in the pulmonary region (alveolar region where gas exchange occurs). This will be a function of the particle aerodynamic equivalent diameter (AED see the glossary) and collection efficiency of the respiratory tract for a given particle AED. When found at high concentrations in the ambient environment, and under conditions of extended exposure, these particles have been associated with changes in lung function, damage to lung tissue, and altered respiratory defense mechanisms (e.g., an impaired ability to naturally eject foreign matter via exhalation). In an occupational setting, exposures (with higher concentrations and/or longer durations) have resulted in similar, if not more severe, health effects. It should be understood that dose and duration of exposure are equally important factors when assessing health effects.
While the oil fires were a contributor to the particulate matter levels (primarily in the form of soot) observed in 1991, particulates also originated from a number of other sources during the same time frame. They were emitted directly from combustion sources (e.g., gasoline engines and crude oil refining operations), wind blown sand, or from the natural transformation in the atmosphere of gaseous emissions such as sulfur oxides, nitrogen oxides, and volatile organic substances. Based on the analysis of samples collected by the US Army Environmental Hygiene Agency (USAEHA) (currently referred to as the US Army Center for Health Promotion and Preventive Medicine) shortly after the Gulf War, analysts have determined that roughly 75% of the particulate matter originated from sand common to this part of the world. Another 23% of the total were soot from the oil fires. The remainder was from miscellaneous sources. 
While still in Iraq following the cease-fire, a severe sandstorm occurred that lasted all day. The sand and dust was so dense that [we] could not see objects even 30 meters distant our guns were deployed 35 meters apart, and we could not see the guns on either side of our position. - Gulf War Veteran
Sand and dust storms are problematic year round in this area of the Middle East, but are worse during the summer when the northwesterly shamal winds occur with greater frequency and intensity. Because sand and dust can obscure vision (without causing actual injury), irritate the skin and sensitive membranes of the eyes, nose, and throat, and aggravate sinus and asthmatic conditions, it was necessary for US personnel in the Gulf to protect themselves against wind blown sand. Consequently, standard personal protective items available to most US personnel included goggles and cravats (large kerchief-type cloths) or similar protection for the airways. Various directives and policy statements directed or advised the use of these items.[9, 10, 11]
Because many US personnel trained, operated, and lived in the desert, health personnel were concerned about the possible adverse health effects of being exposed to high levels of blowing and suspended sand. The grain size of the sand was characteristically small, and some personnel with pre-existing respiratory problems experienced aggravated symptoms. For example, hospital records indicate that US personnel frequently suffered from acute upper respiratory infections as well as coughs, sore throats, sneezing, and runny noses.
It was unlikely that all respiratory complaints experienced during the Gulf War were solely the result of exposure to high particulate matter levels, however. One study conducted among 2,598 personnel stationed in northern Saudi Arabia found that the type of structure in which an individual slept might have been as important a determinant for developing respiratory complaints as exposure to outdoor air pollutants. Personnel who slept in air-conditioned buildings, for example, were much more likely to develop a cough and sore throat than those billeted in tents and warehouses.
Similar findings have been observed in US military training camps where recruits living in modern, energy-efficient barracks with closed ventilation systems were found to be at higher risk from respiratory-transmitted infections. These studies found that personnel living in tightly constructed buildings exhibited more symptoms, because in closed and crowded spaces they were more likely to pass respiratory infections among each other. The Navy Forward Laboratory found that the respiratory infections observed in the KTO during the Gulf War were caused by well-known, common viral and bacterial agents.
The rates of outpatient treatment were slightly higher early in the Gulf War deployment, when personnel tended to be crowded together in transport aircraft, ships, ports of debarkation, and rally or assembly areas. Respiratory disease rates showed a rapid decline as forces dispersed into field positions, but rose again when the weather turned cold. These acute respiratory illness patterns are similar to what is typically seen at military installations in the US.
The health issues surrounding the short- and long-term exposures to particulate matter are discussed in Section V of this report.
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