As large-scale wildfires erupt around the world at an ever-increasing rate and scale, understanding of the health effects of smoke inhalation are of critical importance. While lung and respiratory system side effects are a possibility, researchers at Colorado State University are seeking to understand the impact wildfire smoke has on reproductive health.
Luke Montrose, an assistant professor of environmental and radiological health sciences in CSU’s College of Veterinary Medicine and Biomedical Sciences, began his research into wildfire toxicology while completing his Ph.D. at the University of Montana. The field investigates how organisms react to toxic substances in their local environment — a reality wildland firefighters are all too familiar with.
“Firefighters (are) another at risk group — that’s for obvious reasons,” Montrose said. “They’re highly exposed. But they’re also different from the elderly in that they’re mostly young, mostly fit, otherwise healthy individuals. They’re just getting these really high doses of wildfire smoke.”
During a wildfire, those on the front lines are exposed to particulate matter: solid particles and liquid droplets present in the air. The impact intensity on human health derives from fundamental concepts in toxicology, which distinguish the scale difference found between a campfire in contrast to a major wildfire.
“The key sorts of concepts of toxicology (are) dose, duration and frequency, so your dose will be small because of the duration and the frequency is small,” Montrose said. “If you’re not sitting around a campfire every single day for 10 hours a day, that’s the difference between, you know, these major wildfires, where you can’t get away from it.”
These factors are compounded by the long-term deployment of firefighters, as undergraduate research assistant and on-call Larimer County Sheriff’s Office wildland firefighter Jasper Kehoe explained.
“Firefighters are gone for 14 to 21 days at a time,” Kehoe said. “They work 16 hour shifts every one of those days, and then they get two days off before they do it again. So it is an incredibly time-consuming, time-intensive career.”
When smoke is inhaled and enters the body, an inflammatory response occurs in the central nervous system, including the brain and lungs. These particles reach critical organs through the blood stream, which Montrose said he theorized includes the reproductive system, even without direct exposure.
“The brain is the master hormone regulator of the body, and by causing neuro-inflammation, smoke may actually not need to get to the reproductive tract directly,” Montrose said. “It could influence the reproductive tract by influencing things in the brain.”
Under a branch in his laboratory, Montrose set out to test this hypothesis of wildfire smoke’s impact on reproductive health through a new study. Entitled the Smoke and Wildfire Impact on Male Reproductive Success study, funding is secured through the National Institute for Occupational Health and Safety for a two-year operation.
“As wildfires continue to grow in frequency and intensity due to climate change, understanding the long-term health effects of this exposure is critical not only for those in the field but also for their families and communities. Research like this can lead to better health guidelines, protective measures and ultimately improve quality of life for those at risk.” -Emmie Morales-Arguello, graduate research assistant
Montrose launched the study this past fall and is actively working to recruit 50 to 60 wildland firefighters to participate in year one, with the hope of extending for a second year to include an additional 40 to 50 firefighters, said Frances Rabon, the Montrose Lab project manager.
The study’s sample population is currently limited to male wildland firefighters due to sperm’s regenerative lifespan of 74 days. Comparatively, women are born with all eggs cells they will have in their entire lifetime. This makes for a potential exposure timeline that cannot be as easily pinpointed as sperm.
“(We’re studying) any exposure that happens throughout their entire life, up until the point that that particular egg is released and is going to be potentially fertilized by sperm,” Montrose said. “All of their exposure matters.”
Sample collections are made through at-home tests that firefighters perform themselves, with results then being relayed back to the laboratory for interpretation.
“We give them an at-home sperm collection and analysis kit,” Montrose said. “They are essentially scientists. They collect the sample, they analyze the sample with this at-home test kit and then they send us the results.”
The at-home nature of the tests provides firefighters with several advantages, including not taking away from their limited time off the front lines of active blazes.
“There’s a lot of benefits to the at-home test,” Montrose said. “It’s easy for the firefighters to participate. It’s convenient and private. They can do it in their own home. They don’t have to go to a clinic.”
Montrose is hoping to distinguish between sperm mobility before the fire season, actively during the season and three months afterward to distinguish if fertility levels return to preseason measurements. However, a lengthening fire season is threatening the original design.
“That (design) doesn’t work if there is no fire season,” Montrose said. “If fires occur throughout the entire year, it’s going to be very tricky for us to find a period of time when they’ve received no smoke exposure at all in about a three-month period.”
While the increasing frequency of fires is concerning, it also reinforces the importance of studies like Montrose’s to understand the extent of smoke’s effect on fertility and, in conjunction, family planning for firefighters and their partners.
“As wildfires continue to grow in frequency and intensity due to climate change, understanding the long-term health effects of this exposure is critical not only for those in the field but also for their families and communities,” said Emmie Morales-Arguello, graduate research assistant. “Research like this can lead to better health guidelines, protective measures and ultimately improve quality of life for those at risk.”
The human-based pilot study is further compounded by simultaneous studies that measure the effect of smoke exposure on the reproductive health of mice and bulls. From an ethical lens, using mice allows researchers to perform tests that are unable to be done on humans while also analyzing smoke’s impact across an entire lifetime over a much smaller duration.
Domesticated cattle contain approximately 22,000 genes, 80% of which are directly shared with humans. Comparatively, mice and humans have an approximate 85% compatibility genome rate. The similar reproductive tracts of all mammals — the classification all three species are filed under — results in the three species’ compatibility to successfully study short- and long-term impacts on their reproductive health.
“If you wanted to see how (smoke exposure) affects a male mouse over its life, you can do that in about a year and a half,” Montrose said. “It would take 70 plus years to do that in a human.”
Tangentially, bulls are utilized to better simulate the variety of compounds and entities humans interact with in a natural, nonlaboratory setting during an active wildfire.
“Bulls along the Front Range of Colorado are exposed to the same wildfire smoke that me and you are in nearly the same way,” Montrose said. “Also (not just) about bulls (but) cattle in general, they have a much more similar lifespan to us than do mice.”
Additionally, if an organic compound is found present within bull specimens, exposure to the substance can be isolated at a more concentrated level compared to mice in the laboratory. This allows Montrose and other researchers to easily judge the lasting effects of various chemical structures.
“We can go back to the lab, and we can actually expose mice to those individual chemicals for certain periods of time under much more stringent conditions and understand the mechanism a lot better in those mice,” Montrose said.
With the sensitive nature of the study, Montrose harnessed Kehoe’s familiarity with active firemen and tailored the recruiting material to language firemen would easily understand. Morales-Arguello has also assisted by translating recruiting materials into Spanish to reach a broader population of firefighters. Regardless, recruitment has still remained an uphill battle.
“(Recruitment has been) incredibly difficult — really, very difficult,” Kehoe said. “It was difficult to the point where I had to go in front of my entire team, in front of my crew, and pitch it to them. That’s not an easy conversation — it’s very taboo.”
Some current participants were introduced to the study by their significant others, a notion that further emphasizes the critical need for more research into the field of firefighter family-planning efforts.
“We work in an inherently dangerous job, and any additional education that we can receive, I think, is paramount to increasing our safety of an already dangerous job,” Kehoe said.
Only through overcoming taboo topics of discussion can research be further conducted, including in the discipline of environmental toxicology.
“I’ve come to understand the significant gaps in knowledge surrounding the long-term health risks faced by populations, such as wildland firefighters, who are regularly exposed to harmful pollutants,” Morales-Arguello said. “Reproductive health is often overlooked in environmental toxicology, yet it’s a critical aspect of overall well-being.”
In its next phase of research, the laboratory is hoping to utilize more sophisticated collection and measurement techniques, including testing that is only available at sperm clinics — a next step that would require securing further funding.
“Long-term goals are going to be applying for some more funding to do epigenetics on the samples,” Kehoe said. “(We’re looking to do) temperature-controlled sperm analysis, or sperm transportation, that requires an additional lab to look at it. That requires sending to a specialized facility — one day shipping — things of that nature.”
While more sophisticated measurement techniques are not set in stone yet, it does not deter from the importance of Montrose’s current research and resulting knowledge — an understanding he hopes firefighters will learn from, not be scared of.
“What I’m doing is trying to benefit the health of firefighters, but tangentially, I would never want it to deter firefighters from becoming firefighters or staying firefighters,” Montrose said. “Instead, what we’re trying to do is work hand in hand with firefighter leadership to make firefighting safer and not preclude firefighters from having a family while they’re fighting fires.”
Reach Katie Fisher at science@collegian.com or on Twitter @CSUCollegian.
