Veterans advocates and lawmakers are stepping up pressure on the Department of Veterans Affairs to increase outreach and services for thousands of veterans thought to be at-risk for life-threatening cases of coronavirus: former troops exposed to burn pits in Iraq, Afghanistan and elsewhere.

Sens. Amy Klobuchar, D-Minnesota, and Mike Rounds, R-South Dakota, sent a letter to VA Secretary Robert Wilkie on Tuesday urging his department to be more proactive in caring for veterans with compromised respiratory systems as a result of exposure to burn pits used to dispose of waste at more than 250 overseas locations.

The senators asked Wilkie to follow the department's own COVID-19 response plan, which calls for veterans with service-connected respiratory issues to have access to counseling services through local Vet Centers. But with many of those facilities doing only telehealth counseling, and not all equipped to handle telemedicine, Klobuchar and Rounds say veterans are missing a vital service and also may be at risk during in-person Vet Center visits due to a shortage of critical medical supplies.

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"The VA estimates that over 3.5 million veterans have been exposed to burn pits, and over 200,000 veterans and service members have signed up for the Airborne Hazards and Open Burn Pit Registry to date," the senators wrote. "Given the significant number of at-risk veterans, it is critical that the VA prioritizes efforts to ensure that these brave men and women are able to safely receive care during the current public health crisis."

The letter follows on the heels of correspondence sent to Wilkie on March 31 by five veterans organizations that raised concerns about the availability of COVID-19 testing for VA patients and a perceived failure by the VA to communicate the seriousness of the risk the novel coronavirus poses to veterans with asthma, emphysema and other lung conditions.

That letter, signed by the Association of the United States Navy, Burn Pits 360, the National Vietnam & Gulf War Veterans Coalition, the Non Commissioned Officers Association, Sergeant Sullivan Circle, Veteran Warriors and Veterans for Common Sense, said disparate messages have been sent from the VA's regional offices on COVID-19, ranging from some sending no dispatches, to others not including information on how to receive testing.

In one instance, the groups wrote, a veteran experiencing severe shortness of breath and other symptoms was turned away from the Portland VA medical center because the vet was accompanied by a service dog. With the help of a volunteer outside the VA system, the veteran received medical care in the private sector through the VA's Mission Act urgent care program.

"We are deeply concerned that at least some veterans screened by VA, identified as having symptoms presumed to be COVID-19 and told by VA screeners their symptoms are most likely COVID-19, are then being denied or otherwise prevented from receiving testing for the COVID-19 virus," they wrote.

Burn pits were used at U.S. military bases in Iraq, Afghanistan, Djibouti and elsewhere to incinerate solid waste generated by millions of U.S. troops during deployment, including garbage, rubber, plastics, petroleum, medical waste and more.

Troops reported thick black smoke and dust in the air at all hours of the day and night near the largest burn pits -- clouds that drifted over their work spaces and barracks, causing them to wheeze and cough up dark mucus.

While the VA considers claims for burn-pit related conditions on a case-by-case basis, it points to research in saying that there is no evidence that they cause long-term health problems. According to the VA's Airborne Hazards and Burn Pit Registry page, "most of the irritation" caused by burn pits "is temporary and resolves once the exposure is gone."

As far back as 2006, however, some U.S. military personnel generated reports on the acute health concerns of the burn pits and, later, long-term health risks such as chronic bronchitis, asthma, cardiopulmonary diseases and chronic obstructive pulmonary disease.

During the current pandemic, the VA has posted information on COVID-19 on its main web page, the Airborne Hazards and Burn Pit Registry page and War Related Illness and Injury Studies Center page, warning that the coronavirus poses a risk to older veterans, those in nursing homes or long-term care facilities and those with underlying health conditions, including chronic lung disease, asthma, heart conditions, breathing problems, diabetes, obesity, liver or kidney disease, or who are immunocompromised.

The department also has sent out more than eight million text alerts to veterans about the virus.

But Klobuchar, an architect of legislation that requires the Defense Department to evaluate service members for exposure to airborne pollutants during routine health exams, and Rounds, who worked with Klobuchar and others in mandating the creation of a burn pit "center of excellence" at the VA, say more must be done.

"We request that you provide information at your earliest convenience on how the VA is expanding telehealth capabilities across [Readjustment Counseling Services] facilities to provide veterans, including those with respiratory issues brought on by burn pit exposure, with greater access to care, as well as what the VA is doing to provide all necessary medical and sanitation supplies to Vet Centers and other RCS access points to promote the safety of staff and the veterans they serve," they wrote. "Additionally, we request that you communicate with veterans the resources that are available to them during the pandemic."

As of Tuesday, 5,597 veteran patients in the Veterans Health Administration have been confirmed with COVID-19 and 357 have died in VA hospitals.

-- Patricia Kime can be reached at Patricia.Kime@Military.com. Follow her on Twitter @patriciakime.

Read more: VA Taking Note of 'Alarming' Burn Pit Trends in WWP Survey.