Air Quality and The Gut Microbiome

Poor air quality, especially from wildfires, can harm your health, including inflammation and disruptions to gut microbiome balance.

Wildfire smoke can affect crops, introducing toxins that, when consumed, may disrupt the human microbiome and contribute to health issues like IBS.

Exploring whether improving your microbiome could help mitigate the effects of pollution-related symptoms.

By now, it’s clear that almost everything can influence the composition and health of your gut microbiome. If we think about the path a particulate of pollutant takes when it enters the body, it actually makes sense. Larger pollutant particles are quickly transferred by the lungs to the bloodstream, and then transported to the intestinal tract via mucociliary clearance. This brings such pollutants into circulation. Gaseous pollutants, such as those released by wildfires, have also been linked to systemic inflammation, which has further impacts on the intestine. Systemic or local inflammation, even low grade, can have an impact on the barrier function via the release of inflammatory mediators and products from activated immune cells.

Both outdoor and indoor air contain varying levels and types of pollutants, some of which are more harmful than others. Due to their small size, these pollutants can penetrate multiple bodily barriers, including the skin and mucous membranes. Individuals who have pre-existing immune-related conditions or even certain lifestyles can be at higher risk for adverse health effects due to pollution, which mostly include cardiovascular and respiratory conditions. Most of the most substantiated research to date has focused on ambient air pollution in urban areas, likely due to high levels of industrialization.

Much of the US food supply is grown in California, with a third of the country's vegetables and over three-quarters of the country's fruits and nuts grown there and California's agricultural industry is valued at over $11 billion annually (CDFA, 2022). The state’s crops, including avocados, citrus, and leafy greens, are severely impacted by wildfires and poor air quality exacerbated by Santa Ana winds (Farms.com, 2017). Smoke and airborne pollutants from wildfires can settle on crops, introducing toxins like persistent organic pollutants (POPs), heavy metals, and pathogens (Community Alliance with Family Farmers [CAFF], 2024). These contaminants can negatively affect plant health and, when consumed, may disrupt the human microbiome, which relies on nutrient-rich and uncontaminated food to thrive. Though the immediate risk to human health from trace contaminants may be low, chronic exposure from recurring wildfires poses long-term risks to soil health, crop quality, and food safety (Community Alliance with Family Farmers [CAFF], 2024). This delayed effect could harm both the sustainability of farming systems and the balance of the gut microbiome.

Non-specific abdominal pain, a hallmark symptom of IBS, has been linked to air pollution in studies. Research indicates that young individuals, particularly women aged 15–24, are more likely to experience abdominal pain and seek emergency care during periods of elevated air pollution, including increased levels of CO, PM2.5, SO2, and NO2, some of which compose the mixture that makes up wildfire smoke. Although the exact mechanisms remain unclear, potential factors include increased IL-8 secretion from the small bowel and changes in colonic microflora. Ingestion is a key route for polycyclic aromatic hydrocarbons (PAHs), another component of wildfires, to enter the human body. Research shows that human intestinal microbiota can bioactivate PAHs into estrogenic metabolites—byproducts of chemical metabolism that mimic or interfere with estrogen by binding to estrogen receptors and inducing estrogen-like biological effects. This microbial transformation, observed in the colon, suggests that current risk assessments may underestimate the health risks associated with ingested PAHs.

After a wildfire, prioritize food safety by considering the proximity of the fire to farms, crops, or processing facilities that supply your food. Wildfires can contaminate soil, water, and crops with hazardous materials, while disruptions to refrigeration systems at meat and poultry processing plants can increase the risk of food spoilage or contamination. Be cautious about consuming products from affected areas and stay informed about local reports on potential contamination. If you live near the impacted region, consider testing soil or water on your property, and always observe crops and livestock for signs of damage or decline in health. Taking these precautions can help protect your food supply and health.

The growing concerns about declining air quality, particularly due to events like wildfires, emphasize the need to understand its broader effects on human health. Research increasingly points to a connection between air pollution and overall well-being, including gut health, highlighting the importance of addressing pollution to protect both environmental and individual health.