Wildfire smoke and its neurological impact

The relentless progression of global warming has led to an escalating number of catastrophic wildfires that have wreaked havoc across the world and resulted in the tragic loss of lives and large swaths of land. In addition to direct casualties and property damage caused by the wildfires, the smoke emitted from these fires has significantly exacerbated ambient air pollution levels, both in the immediate vicinity and distant from the fires. This contributes to prolonged periods of poor air quality with detrimental effects on human health globally. While exposure to wildfire smoke has been linked to elevated morbidity and mortality rates for respiratory and cardiovascular diseases, its impact on the neurological system remains largely undisclosed. If there is indeed an association between wildfire smoke and neurological disorder, the potential neurological health burden will be further intensified as climate change continues to drive more frequent and severe wildfire events. Consequently, significant scientific opportunities arise for comprehending the neurological impacts associated with wildfire smoke exposure and identifying the potential mitigation strategies.

Wildfire smoke is a complex mixture of particulate matter at fine (PM_2.5) and ultra-fine sizes, volatile organic compounds, and irritant gases such as nitrogen dioxide and ozone ¹. These constituents possess the potential to elicit deleterious effects on the nervous system via multiple pathways. PM components might be capable of bypassing the blood-brain barrier through axonal transportation of sinus nerves to reach the brain. Whereas irritant gases or volatile / semi-volatile organic compounds containing aldehyde groups in the wildfire smoke can activate sensory nerves in the respiratory tract, leading to the initiation of neurological disorders through oxidative stress and inflammation in the nervous system ^1,2. Furthermore, wildfire smoke exposure may also induce pathological changes in the nervous system via activation of the gut-brain axis and epigenetic modifications.

These hypotheses suggest that there are biological mechanisms underlying the neurological effects of wildfire smoke exposure; however, there is a scarcity of research establishing a robust correlation between wildfire smoke and neurological dysfunction. A limited number of studies suggest that exposure to PM_2.5 originating from wildfire smoke resulted in increased risk of dementia ³, cerebrovascular disease, and headache ⁴. Acute exposure to wildfire smoke may cause reductions in cognitive function within hours or days after exposure ⁵. Nevertheless, these studies have solely focused on the PM_2.5 component of wildfire smoke with a restricted range of neurological outcomes. Given the intricate nature of wildfire smoke as a blend of particulates and gases containing various chemical species, it is imperative to examine potential neurological effects beyond PM_2.5 including organic and gaseous components, explore a broader set of neurological diseases, and ascertain specific susceptible sub-populations to the neurological effects caused by wildfire smoke.

On the contrary, there has been considerable research looking into mental health issues related to wildfires. Most of the current research indicates that experiencing a wildfire is linked to an increased risk of generalized anxiety and post-traumatic stress disorder (PTSD). However, we lack an understanding regarding whether these effects stem from the traumatic experience itself, exposure to wildfire smoke, or potentially both factors combined. Moreover, a significant interconnection may exist between neurological and psychiatric disorders associated with wildfire smoke exposure; it is plausible that wildfires could exacerbate pre-existing mental health conditions and contribute to the subsequent development of neurological disorders and vice versa. However, there is a dearth of research specifically investigating this intricate interconnection.

In the absence of stringent regulations on wildfires and the persistence of climate change, solution-driven research is necessary to identify strategies to minimize the neurological impact of wildfire smoke. Beyond the obvious need to control the frequency and severity of wildfire events, we can take measures to reduce exposure level to wildfire smoke, such as more rigorously employing indoor air purifiers, minimizing outdoor activities, and utilizing personal protective equipment such as N95 respirators. In situations where avoidance of wildfire smoke exposure is impossible, alternative strategies may exist for mitigating its deleterious effects. One option is to take dietary supplementation of nutraceuticals that have antioxidant and antiinflammation properties. Growing body of research suggests that consumption of vitamin B, vitamin C, and omega-3 polyunsaturated fatty acids have been shown to blunt the adverse respiratory and cardiovascular effects of air pollution exposure ^6,7. Additionally, adhering to a Mediterranean-style diet rich in fresh fruits, vegetables such as broccoli, fish, whole grains, and nuts has been shown to reduce inflammatory responses from exposure to air pollution ⁸. As such, these strategies may serve to attenuate the neurological impact to wildfire smoke but have yet to be studied.

The detrimental health effects of wildfire smoke have garnered increasing attention from the scientific community and society at large. However, there remain significant research gaps regarding the neurological implications associated with wildfire smoke exposure. We are calling for a more concerted research effort aimed at establishing a robust link between wildfire smoke exposure and neurological effects in humans and under controlled laboratory conditions, identifying susceptible sub-populations, validating the underlying biological pathways that drive the observed effects, and assessing the efficacy of proposed physical and dietary intervention strategies. This will require substantial collaboration between government, policy makers, the public, and the neuroscience research communities, which is necessary to accelerate the development of interventions that will eventually limit neurological harm from this growing public health crisis.