Democratic presidential candidate and former Vice President Joe Biden claimed without evidence that “more people are coming home from Iraq with brain cancer” than “any other war.” He also suggested that burn pits — open air waste incineration sites — are behind the purported increase.

Existing statistics do not indicate that Iraq veterans are more affected by brain cancer than other veteran groups, although no comprehensive data is available to definitively say one way or the other.

The evidence on the cancer risk of burn pits is likewise inconclusive. A 2011 report by the National Academy of Sciences on the long-term health effects of burn pit exposure in Iraq and Afghanistan found that there was “inadequate/insufficient evidence” to determine whether there is an association with cancer. We didn’t identify any published studies addressing a link to brain cancer since the review.

Biden’s comments came during a CNN town hall in Iowa on Veterans Day, when he was asked by a woman in a military family how he, as president, would address the lack of mental health care and resulting homelessness among service members.

After promising to provide more services to veterans, Biden brought up his eldest son, Beau, who served in Iraq and died from an aggressive brain cancer known as glioblastoma in 2015.

Biden, Nov. 11: And I — if you’re — my son did a year in Iraq. He came home — we lost him, but he came home — and, you know, one of the things we should be looking at is those burn pits that are there. That — it’s just like, you know, when all the firemen in New York went down to 9/11, and so many got cancer, and particularly brain cancer, well, that’s what’s happening. More people are coming home from Iraq with brain cancer than ever before, than any other war.

And we’re in a situation where there’s a direct connection between those burn pits and — and — and taking in that — that — that all that toxin that’s available.

And we should say, anybody who was anywhere near those burn pits, that’s all they have to show, that they — and they get covered, they get all their health care covered.

Biden’s comments echo previous statements he made in a PBS interview about his son and a potential link between military burn pits and brain cancer. In that 2018 interview, Biden said he was not aware of “any direct scientific evidence” tying cancer to burn pits, but postulated that the exposure — which occurred in Iraq and also perhaps in Kosovo, where Beau had gone on a civilian mission — may have played a role in his son’s cancer.

The younger Biden deployed to Iraq for one year, from October 2008 until September 2009, as a captain in the Delaware Army National Guard. In 2013, he was diagnosed with a brain tumor and died two years later at the age of 46.

We’ll present what’s known about burn pits and brain cancer, and also review the available statistics on how common brain cancer is among different veteran groups.

Brain Cancer Statistics

We were unable to find any support for Biden’s claim that “more people are coming home from Iraq with brain cancer than ever before, than any other war.” His campaign did not reply to our request asking for a source for his statement.

The little data that exists does not suggest that Iraq veterans have developed brain cancer at higher rates than those who served in earlier wars.

According to a 2015 Veterans Affairs post-deployment surveillance report, which the agency said was the only “current published data on this topic,” brain cancer prevalence was 0.04% for Vietnam veterans and 0.03% for both Gulf War veterans and those who served in Iraq and Afghanistan post-9/11. The report documents the prevalence and incidence of brain cancer, among other health conditions, for users of VA health care between April 2014 and March 2015. The Iraq War started on March 20, 2003; the conflict in Afghanistan began on Oct. 7, 2001.

The report also lists the age-adjusted frequency of brain cancer among each veteran group by fiscal quarter. While these values fluctuate, the average of these frequencies for all veteran groups is approximately the same, around 4 to 5 cases per 100,000 service members, with post-9/11 veterans on the low end and Vietnam veterans on the high end.

Robert Bossarte, an epidemiologist at West Virginia University and the director of the VA’s epidemiology program at the time of the 2015 report, told us in a phone interview that the brain cancer data in the report do not show much difference between any of the veteran groups.

But he also cautioned against thinking of the post-deployment data as definitive. The statistics, Bossarte noted, only cover one point in time, and are limited to veterans using VA services. That means the figures are missing large numbers of people who have already died and those who get their health care outside of the VA. Only about half of all veterans use the VA for their health care, and usage rates vary by era. As a result, he said, it’s difficult to draw conclusions from the data about how the different service groups compare.

Still, he said he was not aware of “a single manuscript that has suggested there is a higher rate of brain cancer” among post-9/11 veterans.

A VA spokesperson told us in an email that there is “no evidence” of increased brain cancer among Iraq War veterans, or any post-9/11 group, and directed us to the 2015 post-deployment report. She noted that the prevalence of brain cancer increases “in all populations as one ages,” and said that because cancers may take a long time to develop, the VA “continues to study all causes of mortality for the deployed post 9/11 Veteran population.”

The agency said it expects to release an updated post-deployment report in early 2020.

Burn Pits and Brain Cancer?

Biden’s other main claim was his suggestion that burn pits are the reason why some veterans are developing brain cancer. There is little evidence to indicate that’s true, although scientists have not ruled out a connection.

Burn pits are open areas in which trash from a military base is burned, typically because of a lack of other waste infrastructure, including incinerators. Although the U.S. military has significantly reduced the use of burn pits, they once were common throughout war zones in the Middle East and Central Asia.

A 2010 Government Accountability Office report explains that before 2004, burn pits were the only method of waste management that the military used in Iraq and Afghanistan. In November 2009, the report adds, U.S. Central Command reported 50 active burn pits in Afghanistan and 67 in Iraq; by April 2010, this had changed to 184 and 52, respectively, and in August 2010, to 251 and 22.

U.S. Central Command created guidelines for burn pits in 2009, including prohibitions on burning certain materials, such as hazardous waste, plastic, batteries, tires and electronics, but the GAO report found that this guidance was not always followed.

The primary issue with burn pits is that the fumes from the combusted items contain toxins that could be harmful; many soldiers who returned complained of long-term health effects, especially breathing problems, that they believe stemmed from inhaling burn pit smoke.

Given these concerns, the VA asked the National Academy of Sciences to review the evidence on the long-term health effects of burn pits, including an analysis of raw air-sampling data taken from one of the most notorious burn pit sites, Joint Base Balad — a large military base outside of Baghdad that in 2007 burned up to 200 tons of waste every day.

The resulting 2011 report was largely inconclusive. While recognizing the potential for serious health concerns and recommending further study, the committee concluded that it was “unable to say whether long-term health effects are likely to result from exposure to emissions from the burn pit at JBB.” The committee also suggested that long-term health effects might be more generally associated with service in Iraq and Afghanistan, rather than burn pit exposure per se, because of high levels of particulate air pollution on bases as a result of military activities and natural dust storms.

Based on a review of existing epidemiology studies, which evaluated similar, but not identical exposures, such as those experienced by firefighters and incineration workers, there was “inadequate/insufficient evidence” to determine whether there was an association between exposure to combustion products and a variety of health outcomes, including cancer, respiratory disease and circulatory disease. There was slightly more evidence to suggest a connection to reduced pulmonary function, which the report categorized as “limited/suggestive” evidence.

As the GAO report later summarized, while the NAS report “did not determine a linkage to long-term health effects, because of the lack of data, it did not discredit the relationship either.”

For brain cancer in particular, the report explained that while a few studies identified associations between firefighting and brain cancer, the largest cohort study — and the only one that quantified exposure — was negative. Given the mixed results and limitations of the studies, the committee could not make a determination about a potential link — but said that “[b]ecause of the carcinogenic nature of many of the chemicals potentially associated with burn pit emissions, it is prudent to continue investigations of cancer end points and other health outcomes that have long latency in exposed military populations.”

A follow-up report from the National Academy of Sciences in 2017, which focused on an evaluation of the VA’s Burn Pit Registry, reviewed new studies published since the 2011 report relating to burn pits, but the majority were focused on respiratory diseases. None of them addressed cancer.

We also did not find any studies since these reviews that assessed a potential link between burn pits and brain cancer in the biomedical literature.

Brain Cancer Challenges

David Savitz, an epidemiologist at Brown University, and chair of the National Academy committee that conducted the 2017 review, told us in a phone interview that he was not aware of any evidence specifically linking burn pit exposures to brain cancer, and added, “It seems unlikely that we’re going to have such evidence.”

Part of this, he said, has to do with how rare brain cancer is — only about 1% of new cancer cases in the U.S. every year are due to brain tumors, making it hard to study. But also, he said, brain cancer is not “at the top of the list” of diseases that one would expect from burn pit exposure.

“We don’t know what the consequences of burn pit exposure are with a high degree of confidence,” he said, but they go more toward respiratory diseases and cardiovascular risks, not brain cancer.

Indeed, very little is known about what causes brain tumors in general. Jill Barnholtz-Sloan, a brain tumor researcher at Case Western Reserve University, said in a phone interview that there are a few genetic risk factors, including some inherited predisposition syndromes and single-letter DNA changes, but these do not explain the vast majority of brain tumors.

Similarly, the only well-established environmental risk factor that increases risk is ionizing radiation to the head and neck, Barnholtz-Sloan said. High doses of ionizing radiation confer a 2-to-4 fold increase in risk, she said, depending on the type of brain tumor — a fact revealed by studies of children immigrating to Israel in the 1950s who had their scalps irradiated to treat ringworm infection. Smoking, interestingly, is not associated with brain cancer.

The only other well-validated factor is a history of allergies, which appears to provide some protection against developing a brain tumor. Several studies have shown that people with allergies and related conditions, such as asthma, hay fever and eczema, have a reduced risk of brain cancer. While scientists don’t fully understand why this might be, Barnholtz-Sloan said the running hypothesis is that people with these diseases may have revved up immune systems, which may be able to kill cells that turn cancerous more quickly.

The fact that there are not more environmental factors may stem from the brain’s naturally high level of defense. “Evolutionarily, if you think about your brain as the epicenter of your body — your CPU — it’s highly protected,” Barnholtz-Sloan said, noting the multiple membranes surrounding the brain, along with the blood-brain barrier and skull. “Environmental exposures would have to permeate a lot of layers of hard things to get in to affect cells.” This is one reason why it’s so hard to find drugs to treat brain diseases, she said.

While Savitz said that no long-term health effects have yet been clearly linked to burn pit exposure, he said that that should not be interpreted to mean that burn pits don’t cause health problems.

“The absence of evidence is not the evidence of absence,” he said. “There may well be a problem, it’s just a matter of direct evidence.” He is conducting a three-year study to further investigate the long-term health effects of burn pits, but is unaware of anyone doing specific research on cancer.

The VA’s Airborne Hazards and Open Burn Pit Registry allows eligible service members to report health concerns related to burn pits and other airborne hazards. The National Academy of Sciences, however, identified multiple flaws in the registry that led to low completion rates, and recommended numerous changes to increase the registry’s utility. The committee also stated that as a voluntary, self-reported registry, it was “fundamentally unsuitable for addressing the question of whether these exposures have, in fact, caused health problems.”

In an email, the VA defended its registry, saying that it had completed “most” of the academy’s suggested improvements, and that the registry “is a very good tool for health surveillance.” The agency also pointed to its new research hub on airborne hazards and burn pits, which opened in May 2019, and said another consensus report from the National Academy of Sciences is expected in May 2020. That report, the VA said, will focus on the hazards of burn pits and other exposures, and will include cancer outcomes.

Other groups, too, have stepped in to collect data. Burn Pit 360, a nonprofit veterans group, set up its own voluntary registry for people to report health complaints from burn pits. Rosie Torres, one of the co-founders of the organization, told us that as of March 2019, there had been 97 reports of brain cancer out of approximately 6,000 submissions.

Savitz, however, said that neither registry likely will yield any concrete answers. “They can generate possibilities, they can point to where problems may exist,” he said, but they’re “not a substitute for carefully designed research.”

Although future studies may eventually come out to change scientific opinion, there is no direct evidence that burn pits cause brain cancer, and no indication that Iraq War veterans are especially affected by brain cancer, as Biden claimed.

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