Breathing in pollutants can cause a range of respiratory symptoms, but people don’t usually talk about the neurologic symptoms that may be triggered by exposure to pollutants: headaches.
The air you breathe these days is less than fresh due to pollutants such as wildfire smoke, car exhaust, and industrial fumes, to name a few.
Marilyn Howarth, MD, director of community outreach with the University of Pennsylvania’s Center of Excellence in Environmental Toxicology, told Verywell that strong odors and toxic chemicals may trigger people prone to headaches. Even a chemical that’s smelly but not particularly toxic—think sewer gas—could trigger a severe headache in someone with a history of migraines, she said.
People who regularly suffer headaches described worsening symptoms as wildfire smoke settled over the United States this June, leading to increased awareness of air quality and neurological health. The cocktail of chemicals regularly spewed from traffic and industry can irritate a person’s sinuses and exacerbate headaches, Howarth said.
Breathing in industrial chemicals in the home can also trigger headaches, and air pollution is just one of many environmental factors that can worsen symptoms in people with
Many Air Pollutants Can Trigger Headaches
Scientists have studied the effects of wildfire smoke exposure on human health in California, where wildfire seasons have grown more intense over the years. In a recent analysis of emergency room data from 2006–2020, researchers found that exposure to wildfire smoke was associated with more headache-related emergency room (ER) visits.
All types of fires release smoke containing carbon monoxide, carbon dioxide, and particulate matter (also known as PM or soot). Depending on the source of the fire, what is burning, and how hot the fire gets, smoke can contain other chemicals and hazardous air pollutants, according to the Environmental Protection Agency (EPA).
Howarth said the particulate matter in wildfire smoke—as well as diesel exhaust—allows harmful chemicals to linger in the air for longer, increasing the risk of exposure and related symptoms. Particulate matter is present in the air even when there’s not a fire nearby, so breathing in some particles is normal.3 But in the case of a combustion event, particle pollution can carry chemicals like benzene and toluene, which have known toxic effects.
The main components of particulate matter include microscopic bits of ammonia, sodium chloride, black carbon, sulfates, mineral dust, and water, said Anna Pace, MD, a neurologist at Mount Sinai Health System. Research has found that exposure to fine particulate matter (PM2.5) has been directly linked to increased ER visits for migraines in South Korea.
Exposure to “coarse” particulate matter (PM10)—particles up to about four times larger than PM2.5—has also been studied along with other air pollutants in relation to headaches.3 In Taipei and Seoul, researchers found that increased levels of PM10, carbon monoxide, nitrogen dioxide, and ground-level ozone were each independently associated with increased headache-related ER visits.
How Air Quality Triggers Headaches
Experts are still trying to understand how air quality may trigger or exacerbate headaches. Pace said it’s possible that certain air pollutants can trigger the neural pathways involved in the migraine process, or headaches may stem from pollution-induced inflammation in the brain.
If you are someone who is sensitive to odors, your headache is directly stimulated through the olfactory nerves that connect the back of your nose to your brain, Howarth said.
Other chemicals, such as nitric oxide, have been shown to cause a vasospastic reaction in the brain where blood vessels rapidly expand or contract. Howarth said this effect can also trigger a headache, and it may also occur in cases of carbon monoxide exposure where nitric oxide is created as a byproduct.
While more research is needed to determine the effects of specific pollutants, there’s enough data out there to take caution if you are prone to headaches. Poor air quality can interact with an underlying headache disorder, she said, so migraine sufferers should take extra care on high-AQI days.
“It seems that the longer the exposure [to air pollutants], the more likely that someone with an underlying primary headache disorder can experience an exacerbation,” Pace said.
She added that physical activity outside in poor air quality—especially for prolonged periods—can also increase the odds of a headache.
Air pollution-related headache symptoms tend to be similar to a person’s typical headache. Pace said that someone who gets migraines may experience the following symptoms with air pollution-induced headaches:
- Head pain
- Nausea
- Sensitivity to light and sound
You might not be able to pinpoint air quality as the definite cause unless you rule out other triggers, such as light, sound, and food, Pace added.
Exposure Effects May Be Stronger On Hot Days
Studies from outside the United States have also uncovered a possible temperature-related trend in headache occurrences. In both the Taipei and Seoul studies—published in 2015 and 2018, respectively—the incidence of migraines associated with particulate matter was higher on hotter days.
One specific pollutant—sulfur dioxide—was only associated with increased headache visits on warmer-temperature days (73 degrees or higher) in the Taipei study. For comparison, researchers in the Seoul study concluded that sulfur dioxide did not have as significant an association with headaches as other pollutants.
Researchers also considered the role of ground-level ozone, which is more likely to reach unhealthy levels on hot sunny days. Howarth explained that ozone is a secondary pollutant, meaning it is formed in the air only when there is sunlight, volatile organic chemicals, and nitrogen oxides.
Ozone is considered “good” when it occurs naturally in the upper atmosphere—away from where humans breathe—but the gas also can be created at ground level when industrial pollutants react with sunlight. Exposure to ozone may cause headaches and exacerbate seasonal allergies, Howarth said.
Check the AQI Before You Go Outside
You can check the air quality index (AQI) wherever you get your weather report to gauge your possible exposure to pollutants on a given day and location. AQI values span from 0 to 500, with higher numbers representing higher levels of pollution. Values at or below 100 are considered safe or satisfactory.
Pace told Verywell that people may begin to notice symptoms related to poor air quality once the AQI is around 150. Those who are more sensitive to air quality may notice symptoms at slightly lower AQIs, she said.
Sensitive or at-risk groups may include:
- People with heart or lung disease
- People with diabetes
- Older adults
- Children under 18
People who are sensitive to air pollution should consider making outdoor activities shorter and less intense when the AQI inches toward 100 and above. If the AQI is greater than 100, sensitive groups should keep medicine handy in case of symptoms.
When the AQI reaches a level that’s considered unhealthy for everyone—150 and up—more people are likely to experience adverse health effects. It’s important to heed weather alerts about unhealthy air quality, no matter your health history. On bad AQI days, avoid long or intense outdoor activities and consider moving activities indoors.
https://www.verywellhealth.com/air-pollution-headache-7566891
