The Acute and Long-Term Effects of Middle East Sand Particles on the Rat Airway Following a Single Intratracheal Instillation

Abstract

Military personnel deployed in the Middle East have emphasized concerns regarding high levels of dust generated from blowing desert sand and the movement of troops and equipment. Airborne particulate matter levels (PM10; PM < 10 μm) in the region may exceed 1500 μg/m3, significantly higher than the military exposure guideline (MEG) of 50 μg/m3. Increases in PM10 have been linked to a rise in incidences of asthma, obstructive pulmonary disease, lung cancer, and cardiovascular diseases. Male Sprague-Dawley rats received a single intratracheal (IT) instillation of 1, 5, or 10 mg of Middle East PM10 collected at a military occupied site in Kuwait, silica (positive control), or titanium dioxide (TiO2; negative control) suspended in 400 μl sterile saline, or saline alone (vehicle control). Twenty-four hours, 3 d, 7 d and 6 mo postexposure (n = 15/group), organs including lung were evaluated for histopathological changes and for particle contaminants. Bronchoalveolar fluid (BALF) was also analyzed for cellular and biochemical parameters, including cytokines and chemokines. Instillation of silica resulted in early, pronounced, sustained inflammation indicated by significant increases in levels of total protein and neutrophils, and activities of lactate dehydrogenase activity and β-glucuronidase activity. Lower magnitude and transient changes using the same markers were observed in animals exposed to TiO2 and Middle East PM10. The results suggest that for acute exposures, this Middle East PM10 is a nuisance-type dust with relatively low toxicity. However, since average deployment of military personnel to the Middle East is 180 d with potential for multiple follow-on tours, chronic exposure studies are needed to fully understand the pulmonary effects associated with Middle East PM exposure.