Public Health Command examines air in Southwest Asia
August 23, 2012
Air, and the potential health effects from breathing it, may be the environmental health question of most interest to emerge from the last 10 years of operations in U.S. Central Command.
With partners in the Department of Defense, Veterans Affairs, other government agencies and academic institutions, U.S. Army Public Health Command has been involved since the first Gulf War in characterizing the air in Southwest Asia.
In this mostly dry, desert-like part of the world, the air routinely measures higher in particulate matter than almost all locations in the continental U.S. and commonly exceeds U.S. Environmental Protection Agency standards.
"Particulate matter, or PM, is defined generally as a small mass of solid or liquid matter that is breathable. Organic and inorganic chemicals in this air can be attached to these small masses," explained Jeffrey L. Kirkpatrick, director of Health Risk Management at USAPHC. "Examples of PM that we have found in our (CENTCOM) sampling include dust from the terrain and weather conditions, primarily dust storms, and chemicals and compounds from oil fires, vehicle fuel and combustion, industry, and other human activities."
Both naturally occurring and man-made PM have potential to cause health effects.
"We see this naturally occurring particulate matter as a potential cause of short-term, primarily irritant, effects on the respiratory system." said Coleen Baird, a physician who heads the USAPHC Environmental Medicine Program. "It is an open question whether geologic sources of pollution are causing more serious and long-term illness. We are also concerned about other local and regional sources of particulates, such as industrial activity and military and indigenous waste disposal (burn pits)."
While service members have expressed concern about the health effects associated with breathing air in the CENTCOM region and especially with exposure to smoke from burn pits, scientific results to date are mixed.
"We know that upper respiratory effects due to inhalation exposures have occurred," explained Baird, "These include sore throat, cough, eye irritation, runny nose and other cold-like symptoms.
"We also know that chronic respiratory conditions such as asthma and chronic bronchitis may be worsened," she added.
But despite multiple studies by USAPHC and other government and non-government scientists, the question of whether individual service members will suffer long-term health effects from PM in the air remains unanswered.
"The evidence to date does not support an association between deployment to Southwest Asia and chronic respiratory or cardiovascular conditions, nor does it disprove the existence of such an association," Baird said.
"Based on medical literature and scientific studies in other occupational environments, long-term health effects are plausible," said Joseph Abraham, an epidemiologist in the USAPHC Environmental Medicine Program. "However, long-term health effects have not been consistently observed on a population basis. We've looked at, and are continuing to monitor, respiratory and cardiovascular disease diagnoses. With one exception, they have not significantly increased."
That exception is a non-specific International Classification of Diseases diagnostic code, ICD9 code 490, which stands for "bronchitis, not specified as acute or chronic." This diagnosis, Abraham said, appears to have increased over the last 10 years among military personnel.
But it isn't certain why.
"It is unclear whether this diagnosis reflects an increase in a true chronic disease, bronchitis associated with viral or bacterial illnesses, or simply with changes in health care utilization patterns," Abraham said.
Most studies done by USAPHC and other organizations are retrospective, looking at various records and trying to link medical conditions, primarily respiratory or cardiovascular, and inhalation exposures.
"Most of our studies have looked at the rates of medical visits for which a respiratory or cardiovascular disease code has been entered in DOD medical databases," Baird explained. "We correlate these medical encounters with other databases that tell us how often, where and when a Soldier has deployed and what the general environmental conditions were at or near those locations."
The fact that almost 70 percent of service members report respiratory symptoms in post-deployment questionnaires is cause for concern. However, USAPHC physicians and epidemiologists have not observed a consistent link between deployment and an increase in respiratory or cardiovascular diagnoses.
USAPHC scientists acknowledge their studies have limitations, however.
"Asking whether a population, in this case service members deployed to Southwest Asia, will experience chronic, long-term health effects from environmental exposures is a complicated and nuanced question," Baird said.
One complicating factor is that the data available are not as specific or detailed as physicians and epidemiologists attempting to look back and draw conclusions about health effects would like.
In addition to changing health care utilization discussed above, clinicians may choose a diagnosis code that doesn't correspond to a standardized clinical definition of a disease, Abraham explained. When scientists make decisions about how to interpret codes, there is a potential for error.
As well, medical records contain limited information on behavioral and other individual-level factors, like cigarette smoking and overall fitness, that may affect the relationship between air pollution and health status.
It's not just medical data that cause uncertainties.
"There are literally thousands of environmental surveillance reports associated with air quality in Southwest and Central Asia from the last 10 years," Kirkpatrick said. "However, there is variability, and so uncertainty, in the degree to which these data represent usual conditions and exposures of personnel."
Much research has been conducted to characterize air pollution health effects throughout the world. But associations between short-term exposure to air pollution and severe health effects in most studies have been observed in populations of children, older adults, and among individuals with pre-existing health conditions, Abraham said.
"The additional risk to health associated with naturally occurring particulate matter is small, so the long-term cumulative effects of exposure are often only observed in older age groups with relatively higher baseline risks of having adverse health events," he added.
Other researchers have found evidence of associations between deployment experiences and chronic disease.
Researchers at the Veterans Affairs Medical Center in Northport, New York, have published several studies linking asthma and lung function abnormalities with deployment to Iraq. A total of 49 Soldiers were referred for lung biopsy to Vanderbilt University Medical Center, 38 of whom were diagnosed with constrictive bronchiolitis, a chronic lung disease, and all of whom were considered to have abnormal biopsy results. The biopsies and diagnoses are undergoing independent review at National Jewish Medical Center in Denver. Representatives from both studies are working with the DOD and the VA to continue study of potential health effects from PM exposure in CENTCOM and recommend appropriate medical treatments and monitoring.
Environmental Medicine Program staff has not found literature that addresses presence or absence of cardio-respiratory effects in Southwest Asia's indigenous population.
"I would not say that indigenous populations are not experiencing cardio-respiratory effects," Abraham said. "We simply lack the data."
USAPHC, the DOD and the VA are continuing to evaluate long-term health effects of deployment-associated inhalational exposures, Baird said. Most recently, the two organizations hosted an Aug. 21--23 symposium to discuss airborne hazards in the deployed environment and related health questions.