Among the most prevalent health conditions reported by post-Sept. 11 veterans are hearing loss and tinnitus.
Nationally, the Department of Defense estimates that 13 to 18 percent of U.S. troops experience hearing loss and tinnitus, or ringing in the ears. According to the Defense Department's Hearing Center of Excellence, more than 350,000 service members have reported tinnitus after overseas tours in the current conflicts in Iraq and Afghanistan, and more than 250,000 have reported hearing loss during this era.
And in a recent report, the Department of Veterans Affairs found hearing loss and tinnitus were the most prevalent service-connected disabilities for veterans who began receiving compensation in 2011.
MPR News analyzed data showing every diagnosis VA doctors gave veterans between 2003 and 2012 at VA hospitals across the state, including Minneapolis, St. Cloud, Fargo and Sioux Falls.
There's been a dramatic increase in these problems among Minnesota veterans over the last decade.
In 2012, the VA saw veterans with hearing loss 41,640 times -- an increase of 146 percent over 2003, when the VA saw veterans with hearing loss just 16,911 times.
Rates of tinnitus have increased even more. There were 15,520 diagnoses of tinnitus and other disorders of the ear in Minnesota in 2012 - a whopping 326 percent more than a decade ago, when the VA saw veterans with tinnitus and other disorders of the ear only 3,635 times.
According to the DOD, compensation for these disabilities is impossible to assess, since most veterans' benefits are based on calculations associated with various other individual disabilities.
The causes of hearing problems in the military are many.
Service members in war zones are routinely exposed to hazardous levels of loud noise from equipment, weapons, vehicles, blasts or aircraft.
Former Army paratrooper Patrick Nelson says he suffered hearing loss during his three tours to Iraq and Afghanistan. In Afghanistan in 2005, Nelson survived a deadly explosion that killed two soldiers he was with. He now experiences tinnitus.
"It's just a constant ringing," said Nelson. "I usually don't notice it during the day but if I'm ever in a quiet room, or especially at night lying down, it's pretty easy to notice it then."
Studies have also found that service-related tinnitus can be caused by head injury, which is common in the current conflicts in Iraq and Afghanistan.
In an effort to track hearing problems in recent years, the military began surveying returning troops with health assessment questionnaires that include questions about tinnitus.
DOD has also launched a major effort to prevent hearing problems during military service. The department acknowledges the challenges to prevention. Despite widespread education in the military about hearing problems and how to prevent them, soldiers in combat are not always willing or able to use hearing protection when they need it because doing so could jeopardize their safety in other ways.
Respiratory problems are also common among troops returning from Iraq, Afghanistan and Kuwait, where soldiers have been exposed to high levels of dust, smoke, sand, pollution and other environmental hazards such as toxic metals, acids, chemicals and bacteria.
The Minnesota numbers reflect this trend.
An MPR News analysis of VA health data shows a sharp increase in respiratory diseases. Acute respiratory infections were up 45 percent in 2012 with 9,172 cases, compared with 6,324 in 2003. Chronic Obstructive Pulmonary Disease and allied conditions rose from 18,066 in 2003 to 23,058 last year, an increase of almost 28 percent.
Some respiratory problems could be linked to the practice of using so-called burn pits to dispose of waste, where the U.S. military has openly burned garbage and hazardous materials, including chemicals, paint, medical and human waste, metal, aluminum cans, munitions and other unexploded ordnance, petroleum and lubricant products, plastics and Styrofoam, rubber, wood, and discarded food.
Many Minnesota veterans have been exposed to such smoke overseas.
Iraq veteran Eric Waage experienced the burn pits in Balad, Iraq on deployment from 2008 to 2009 with the Minnesota National Guard.
"This was essentially a large smoldering bonfire at ground level that sent clouds of smoke and ash from all kinds of burning wastes all over the base," said Waage. "When the wind was aligned to send the smoke directly over our battalion area, our eyes would sting and lungs would burn. Moving away from the smoke was not an option, you had to stay put and keep doing your job."
Coupled with the burn pits were other environmental hazards, Waage recalls.
"The environment was one of an endless string of dust storms that were so thick the air glowed pumpkin orange in the noon sun. They could last for days and dust would enter through every possible entry point in your body," said Waage.
"You could only wear a dust mask so long until you just had to take it off. I'd wake up and find it crumpled up under my head. While a lot of us tried to regularly use protective equipment against particles, noise, and other hazards, full-time protection was often not realistic in the wartime setting. Most military folks, including me, are loath to complain about smoke and dust exposure when many have had impacts in more direct and immediate ways."
Nevertheless, Waage says he's been concerned about his respiratory health ever since he got home in 2009.
"It seems as if I have more respiratory symptoms now when I get sick than I did prior to deployment," Waage said. "I don't know if this is just a blip, or if there is a connection to my service. I do think my health has changed somewhat from the experience. Almost any illness that I get now seems to somehow find its way into my lungs. I think my lungs are weaker and less able to clear out particles or fight off sicknesses."
Studies have suggested a possible link between exposure to burn pits and health problems. But results have been inconclusive because of insufficient data.
The study suggested that burn pits, together with other environmental hazards troops encounter in Iraq and Afghanistan, could be associated with long-term health problems, and called for more data to be collected to monitor for diseases that may not surface for years.
The Army sampled air from around Iraq and Afghanistan and has found that the sand and dust present in the theater was "not demonstrably different from the sand and dust in desert regions of the United States."
The Department of Defense has said there is "no evidence to suggest that service members deployed to U.S. Central Command are being disproportionately affected by environmental factors."
In 2009, the military updated its policies on burn pits to prohibit the burning of hazardous materials such as certain medical waste, batteries and tires, and whenever possible, to situate them where the smoke would not blow over work and living quarters.
Both DOD and VA are collecting data on returning troops' respiratory conditions.