Battlefield and Terrorist Explosions Pose New Health Risks

Newswise — High concentrations of nitrogen dioxide gas — inhaled for even very brief periods following fires, explosions of military munitions or detonations of terrorist devices — could cause serious lung damage, scientists reported today at the 233rd national meeting of the American Chemical Society.

Dr. Zengfa Gu, M.D., Ph.D., and colleagues at the Walter Reed Army Institute of Research, Silver Spring, Md., reached that conclusion based on experiments with laboratory rats that were exposed to the toxic gas. Gu explained that previous research showed that chronic exposure to low and moderate levels of nitrogen dioxide could damage the lungs. However, there was no clear information on the health risks of brief, high-level exposures lasting only a few minutes.

Nitrogen dioxide, a reddish-brown gas with a sharp, biting odor, is most familiar as an air pollutant. Released to the air from the exhaust pipes of automobiles and the burning of coal and other fossil fuels, it is an ingredient in photochemical smog. Nitrogen dioxide also is a common indoor air pollutant that is released from gas ranges and other indoor combustion sources. It can cause nose, eye and more serious health problems. Government industrial health regulations limit workplace exposures to 5 parts per million (ppm).

The gas, however, also forms when the heat from fires and explosives makes nitrogen and oxygen in the air combine to form nitrogen dioxide.

Gu said information about such brief exposures to nitrogen dioxide is important for the military because in battlefield situations, personnel easily can be exposed to high concentrations of nitrogen dioxide. Civilians also could be exposed as a result of terrorist bombings. Similar exposure could occur among civilians trapped in fires for several minutes before being rescued.

"This research is very important," Gu said. "The results tell us that if [one encounters] an environment with high concentrations of inorganic fire gases, serious lung injury may be induced rapidly. So this research provides the scientific background for prevention of inhalation trauma and the treatment of inhalation injury."

In their experiments, scientists exposed laboratory rats to varying concentrations of nitrogen dioxide — 100 ppm, 500 ppm, 1,000 ppm and 2,000 ppm — for 5 minutes. They monitored effects of nitrogen dioxide during the exposure and examined the lungs afterward for signs of damage.

"The experimental data showed that after exposure to high concentrations of nitrogen dioxide for only five minutes, the respiratory function was extremely changed," Gu said. "Breathing rate and depth were sharply inhibited; lung edema was rapidly induced, [and] acute and delayed lung damage occurred."

Gu said that the research represents the first real-time measurements of breathing changes due to the inhalation of nitrogen dioxide gas. No other laboratories have conducted the same research due to technical challenges, which involved designing a special exposure chamber and computer software to make accurate measurements on living animals.

The American Chemical Society — the world's largest scientific society — is a nonprofit organization chartered by the U.S. Congress and a global leader in providing access to chemistry-related research through its multiple databases, peer-reviewed journals and scientific conferences. Its main offices are in Washington, D.C., and Columbus, Ohio.

The poster on this research, INOR 867, will be presented from 8 -10 p.m., Monday, March 26, at the Hyatt Regency Chicago, Riverside Center, during "Sci-Mix," and from 7-10 p.m., Tuesday, March 27, at the Hyatt Regency Chicago, Riverside Center, during the symposium, "Energy and Environmental Inorganic Chemistry."

Zengfa Gu, M.D. Ph.D., is with the Department of Respiratory Research, Walter Reed Army Institute of research, Silver Spring, Maryland.

ALL PAPERS ARE EMBARGOED UNTIL DATE AND TIME OF PRESENTATION, UNLESS OTHERWISE NOTED

The poster on this research, INOR 867, will be presented at 8 p.m., Monday, March 26, during "Sci-Mix," and at 7 p.m., Tuesday, March 27, during the symposium, "Energy and Environmental Inorganic Chemistry." It is embargoed for 8:00 p.m., Central Time, Monday, March 26.

INOR 867Lung edema caused by brief inhalation of high concentration nitrogen dioxide in awake rats

Program Selection: Division of Inorganic ChemistryTopic Selection: Energy and Environmental Inorganic Chemistry

Zengfa Gu1, Adolph J Januszkiewicz1, Thelda I Atkin2, Venee I Morthole2, and Gary D Coleman2. (1) Department of Respiratory Research, Walter Reed Army Institute of Research, 503 Robert Grant Ave, Silver Spring, MD 20910, [email protected], (2) Division of Pathology, Walter Reed Army Institute of Research

AbstractNitrogen dioxide (NO2) is a toxic inorganic gas and could be released to the environments from burning nitrogenous materials in fire or explosions. It has been reported that exposure to low to middle level NO2 induces pulmonary injury. However, effects of exposure for very short time to high concentrations of NO2 on lung water balance have not been clearly described. This study investigated the development of lung edema after exposure to different concentrations of NO2. Awake male Sprague-Dawley rats (250-380g) were randomly grouped (n=9) and placed into tube restrainers attached to an exposure chamber with constant gas flow. Rapid switching of exposure gas composition was accomplished using electric solenoid valves. Prior to exposure, animals were allowed to breathe USP air, then, exposed to 100, 500, 1000, and 2000 ppm for exact 5 min respectively. Lungs in each animal were collected. Lung wet/dry ratio was calculated and showed 1.2, 1.2, 1.5 and 2.5 for 100, 500, 1000 and 2000 ppm group respectively. Lung edema was confirmed by Histopathological examination. These results suggest that high concentrations of NO2 inhaled from environments even for very short time could cause pulmonary damage.

Researcher Provided Non-Technical Summary

Briefly explain in lay language what you have done, why it is significant and what are its implications (particularly to the general public)

Nitrogen dioxide (NO2) is a toxic inorganic gas and could be released to the environment from burning nitrogenous materials in fire, or explosions of military munitions, even a detonation of terrorist devices. It has been reported that exposure to low to middle level NO2 induces pulmonary injury. However, the health risk of exposure for very short time to high concentrations of NO2 has not yet been clearly described. In the battlefield environment, military service personnel have a variety of realistic possibilities of exposure to high concentrations of nitrogen dioxide. This study investigated the changes of respiratory function after exposure to different concentrations of NO2 in awake male Sprague-Dawley rats.

Though this study is specifically designed to look at combat applications, findings might also be extrapolated to the outcome of inhalation caused from the civilian fire environment where delayed evacuation may result in encountering inorganic toxic gases at high concentrations.

We have done: (1) the effects of high concentration NO2 inhalation on breath rate and depth, and ventilation functions, (2) the lung water balance after inhalation of NO2, (3) measurements of lung weight, (4) pathological examination of damaged lung., (5) risk analysis.

The experimental data showed that after exposure to high concentrations of nitrogen dioxide for only five minutes the respiratory function was extremely changed: (1) breath rate and depth were sharply inhibited, (2) lung edema was rapidly induced, (3) acute and delayed lung damage occurred.

This research is very important. The results tell us that if encountering an environment with high concentration inorganic fire gases the serious lung injury may be induced rapidly. So that this research provides the scientific background for prevention of inhalation trauma and the treatment of the inhalation injury.

How new is this work and how does it differ from that of others who may be doing similar research?

The pulmonary ventilation research is new. According to the literature search, no other laboratories in the United States or around the world have conducted the same research in measurement of real-time breath changes due to the technical difficulties. We designed the exposure chamber and other measurement software, which has been mentioned in the abstract, to accomplish the research goal.