A review of the data developed as a result of sampling conducted immediately after the Gulf War indicates that particulate matter levels in the air were significantly high and that concentrations often exceeded the levels considered safe for the protection of human health. The data also indicate that there was a significant mass of particles in the PM10 size range. Particles in this size range have the potential for entering the thoracic region of the respiratory tract. Both of these factors suggest that some personnel with pre-existing respiratory problems may have experienced aggravated symptoms. For example, the inhalation of ambient levels of particulate matter could have resulted in several acute symptoms and could have aggravated asthmatic conditions in some personnel. A number of studies have been completed on the acute effects of particulate matter exposure. Typical symptoms experienced by US personnel were cold- or flu-like and included cough, runny nose, eye and throat irritation, and shortness of breath. These symptoms are generally short-term and reversible.
Although high levels of particulate matter were observed, these concentrations fell within a range consistent with background levels observed in Kuwait where the average level of PM10 is nearly 600 m g/m3, the highest in the world. Average PM10 concentrations measured by the USAEHA during a nine-month period in 1991 ranged from 265 to over 670 m g/m3. This range is about 2 to 5 times greater than the US standard of 150 m g/m3. The chemical composition of the samples indicated that roughly 75% of the airborne particulate matter consisted of clays, primarily calcium and silica that originated from the sand indigenous to this part of the world. Another 10% to 23% were carbon (soot) that originated from a combination of sources including the oil fires and various industrial sources, and less than 10% came from miscellaneous sources.
Respiratory complaints experienced during the Gulf War were not solely the result of exposure to high particulate matter levels, however. The Navy Forward Laboratory found that respiratory infections observed during the Gulf War were caused by well-known, common viral and bacterial agents, and in many cases were aggravated by the crowded living conditions experienced by some US personnel.
Thomas et al (2000) examined the potential for adverse health effects from long-term exposure to silica and soot. It should be noted, however, that these concerns were based on occupational studies for which exposure and health hazard information exist and are probably not the same as those received by Gulf War veterans. When found at high concentrations in an occupational environment, and under conditions of extended exposure, the medical literature notes that 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).
As discussed in Section V, the critical dose (i.e., the amount of a contaminant actually taken in by the body necessary to cause some adverse health effect) is as much a function of the length of time an individual was exposed as it is the actual concentration to which the person was exposed. [See the discussion on cumulative exposure and dose in Section VI.] Therefore, an exposure to a high concentration of a contaminant becomes problematic only when the duration of the exposure results in the individual receiving a significant dose over an extended period of time. For example, while US personnel were exposed to high levels of particulate matter during the Gulf War, the duration of these exposures was generally short (as compared to occupational exposures which can occur over a working lifetime), and thus the doses received by US personnel were likely to have been small when compared to an occupational exposure of longer duration.
The Thomas report supports this position. The report notes that the estimated exposures and total dosages to silica and soot were below human health protection standards, and therefore, chronic health effects would not be expected to occur. That is, the results suggest that there is not a link between the exposures to silica and soot received in the KTO and the unexplained illnesses reported by some Gulf War veterans. Reversible, short-term or acute effects attributable to the high levels of particulate matter, however, may have occurred. These would include runny nose; eye, nose, and throat irritation; cough; and shortness of breath. These acute symptoms would be due primarily to the high particulate content, rather than solely to the silica or soot content of the air.
These conclusions are based on inhalation exposure scenarios involving individual contaminants of concern (i.e., silica or soot) and do not take into account the possible synergistic effect of other toxic compounds that may be present. Further research is required to develop an understanding of the dose-response mechanisms associated with these types of exposure.
Dermal exposures to particulate matter were also examined. Silica dusts have been associated with specific types of dermatitis or skin inflammation. The Thomas report notes that these irritations are not expected to produce long-term adverse skin disorders since longer exposure periods (typically greater than three years) are normally required before these symptoms begin to occur.
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