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Can air pollution affect your period? New research says yes
When we think about the effects of air pollution, we usually picture smoggy skies and maybe a cough or two. But new research suggests it could also be affecting something way more personal: your menstrual cycle.
In a first-of-its-kind study, our research team at MIT’s Senseable City Lab and the University of Colorado Denver, in collaboration with Clue, examined how exposure to air pollution affects menstrual health.
We analyzed over 2.2 million menstrual cycles tracked by 92,000 Clue users in 230 cities across the U.S., Brazil, and Mexico. Our findings, published in The Lancet Planetary Health, add new evidence that the environment we live in can shape our reproductive health, and that menstrual cycles deserve more attention in public health research.
Air pollution and health
Air pollution is one of the biggest environmental health risks worldwide. The World Health Organization estimates it causes more than 4 million premature deaths every year (1). Most research to date has focused on how polluted air affects the lungs and heart, linking it to conditions like asthma, chronic respiratory disease, stroke, and heart attacks (2).
In recent years, scientists have started exploring the effects of air pollution on reproductive health too, particularly on fertility and pregnancy. Studies have linked air pollution to infertility, preterm birth, and low birth weight (2).
But the menstrual cycle, a key indicator of reproductive and overall health, has been largely overlooked in the conversation.
What is PM2.5, and why should we care?
Our study focused on a type of air pollutant called PM2.5. This stands for fine particulate matter that’s 2.5 microns or smaller (about 30 times smaller than a human hair). These tiny particles come from sources like car exhausts, power plants, and factories (1). Because they’re so small, they can travel deep into the lungs, enter the bloodstream, and cause inflammation in the body (2). There are many types of air pollutants, but PM2.5 has the strongest link to health problems (1).
We wanted to find out if being exposed to this kind of pollution over time could affect menstrual cycles—something that hasn’t been studied on a large scale before.
What we found
We looked at two types of pollution exposure:
Short-term exposure: pollution levels during a single cycle
Long-term exposure: average pollution levels in a user’s city over all of their tracked cycles
We found that people living in cities with higher long-term PM2.5 exposure were more likely to have atypical cycles, especially longer ones. This could signal changes in the endocrine system, which controls your hormones, including the ones that regulate your period.
Short-term exposure didn’t significantly impact that same cycle, but we did see signs that air pollution exposure during earlier cycles might still play a role—suggesting that environmental exposures may affect the cycle with some delay.
Why this research matters
Menstrual cycles are more than just a monthly event—they’re a reflection of your overall health and well-being. Variations in cycle length can happen for many reasons, including changes in stress, travel, diet and exercise, illness, or other external factors (3-5).
Our research adds to this growing understanding by suggesting that the quality of the air we breathe, specifically long-term exposure to air pollution, may influence menstrual cycle patterns.
This study is one of the first to use cycle data tracked in real-time from an app like Clue to dig into how environmental factors may affect menstruation on a large scale. Combined with satellite-based pollution estimates, we were able to examine menstrual cycle patterns across thousands of individuals in diverse geographic and environmental contexts. This approach allowed for a level of scale and specificity that hadn’t been possible in menstrual health research before.
Clue's user-generated data helped researchers uncover patterns that might’ve been invisible otherwise. It’s a powerful reminder of how tracking your cycle can contribute to both personal insights and scientific progress.
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What you can do to protect your health (and your cycle)
While we can’t always control the air we breathe, there are steps you can take to reduce your exposure and better understand how your body responds:
Check your local air quality: Many cities provide real-time data online or through apps. On high-pollution days, consider limiting outdoor activities to reduce exposure (1).
Track your cycle: Tracking with apps like Clue can help you understand what’s typical for your body so you can spot changes earlier.
Talk to your healthcare provider: If you notice changes in your cycle or are experiencing symptoms that affect your quality of life, tracking data can help guide those conversations.
This is just the beginning
This research is part of a bigger conversation about how environmental factors affect our health, and why menstrual and reproductive health needs to be part of that conversation. And with the climate crisis continuing, understanding how our environment affects our bodies is more urgent than ever.
There’s still more work to be done to understand in more detail how air pollution may affect the menstrual cycle. We hope that our study leads to further research into the biological mechanisms that link pollution to the functioning of the menstrual cycle. But this study is a step forward in showing that menstrual health is not just personal—it’s also environmental.
To every Clue user who contributed their data: thank you. This work wouldn’t have been possible without you.
