CAMBRIDGE, Mass., May 16, 2025 (GLOBE NEWSWIRE) -- Researchers at MIT’s Senseable City Lab and the University of Colorado Denver, in collaboration with the Clue app, have published the largest study of its kind examining the impact of air pollution on menstrual health across multiple countries. The research, just published in The Lancet Planetary Health, analyzed data from 2.2 million menstrual cycles tracked in Clue, across 230 cities in the United States, Mexico, and Brazil. The study found that higher concentrations of fine particulate matter (PM2.5) in the air correspond with increased frequency of menstrual cycle irregularities.

While air pollution research has traditionally focused on respiratory or cardiovascular effects, impacts specific to women's health have been largely overlooked— a reflection of the persistent gender health gap in scientific research. This study brings women's health into focus, revealing how environmental factors influence menstrual cycles in unexpected ways, while also demonstrating that when researchers examine sex differences, they can uncover critical health effects that might otherwise remain invisible.

Long-term Pollution Exposure Shows Measurable Effects on Menstrual Health

Specifically, the study found that:

• Long-term exposure to higher levels of PM2.5 is associated with a higher percentage of abnormal menstrual cycles, particularly longer cycles, a potential sign of disrupted endocrine and reproductive functioning
• While short-term pollution exposure did not show immediate effects, PM2.5 exposure in prior cycles appeared to affect cycle regularity later
• The study demonstrated that data from cycle tracking apps can be used to answer important questions on the impact of environmental factors on menstrual and reproductive health
  

"Menstrual cycle length and variability are a vital indicator of women's health. Research has shown that highly variable menstrual cycles can be associated with an increased risk of premature mortality, cardiovascular disease, type 2 diabetes, cancer, and infertility. The impacts of pollution on menstrual cycle length have been understudied, as few epidemiologic cohorts track menstrual cycle information." - Priyanka deSouza, PhD, MSc, MBA, MTech.

"This study gives us a unique look at how air pollution might affect menstrual cycle length in three different countries. The researchers used data from the Clue app to evaluate long and short cycles in the same person, in relation to air pollution levels in their city. The results suggest a link between PM2.5 (a type of air pollution) and cycle length. PM2.5 is already known to harm human health, especially the heart and lungs. This study shows that it may also affect ovulation and menstrual health." - Shruthi Mahalingaiah, MD, MS, Harvard T. H. Chan School of Public Health and Massachusetts General Hospital.

How Clue’s Tracking Technology Can Advance Reproductive Health Science

Rather than relying on retrospective self-reporting as previous studies have done, the research for this study utilized longitudinal cycle tracking data from Clue users, combined with satellite measurements of air pollution levels. This study underscores the power of digital health tools, such as the Clue app, to surface meaningful population-level patterns—especially in areas where traditional research has fallen short.

"Dealing with personal and sensitive data always poses ethical challenges. In this study we were very careful in dealing with such data sets, but we were able to highlight how environmental stressors can have such deep and personal effects," says Fábio Duarte, of MIT Senseable City Lab.

"Clue is helping close the gender health gap by making large-scale research into women’s health faster and more feasible than ever before," said Amanda Shea, Fractional Chief Science Officer at Clue. "By analyzing millions of de-identified cycles tracked in the app alongside environmental data, we've taken a new approach to exploring how external factors like pollution might influence reproductive health. This kind of research offers people meaningful insights into their bodies, helping them recognize patterns earlier and make more informed decisions about their health."

Further Research and What Women Can Do

This research builds on prior toxicological and epidemiologic work linking air pollution to reproductive outcomes like preterm birth and infertility, but fills a critical gap by focusing on menstrual health—an under-researched indicator of overall well-being. These findings reinforce calls for improved air quality standards and environmental justice for communities most at risk.

While further research is needed to confirm these effects and better understand the biological mechanisms behind them, especially as the climate crisis intensifies and pollution persists, advancing understanding of how environmental factors impact women’s health is more important than ever.

For those concerned about air quality's potential impact on their health, Clue’s science team recommends that they:

• Monitor air quality and limit exposure during high pollution days: In many cities, you can check daily air pollution levels in your area through local environmental agencies or air quality monitoring apps. Limiting outdoor exposure when air pollution levels are high can help protect your health.
• Use the Clue app to track your cycle: By tracking your periods and related cycle symptoms over time, you can build a clearer picture of what’s typical for your body. Understanding your own patterns makes it easier to spot changes early—so you can take action or seek support when something feels off.
• Consult healthcare professionals: Talk to your healthcare provider if you have any concerning cycle changes or are experiencing symptoms that impact your quality of life. Sharing your cycle tracking data can help inform these discussions.
  

Methodology:

The study analyzed data from 2,220,281 cycles collected between 2016 and 2020 from 92,550 Clue users across 230 cities in the U.S., Mexico, and Brazil. Satellite-derived estimates of PM_2.5 concentrations were aggregated at the city level, and cycle-level data were matched to the corresponding PM_2.5 exposure.

About the University of Colorado Denver

Millions of moments start at CU Denver, a place where innovation, research, and learning meet in the heart of a global city. We’re the state’s premier public urban research university with more than 100 in-demand, top ranked bachelor’s, master’s, and doctoral degree programs. We partner with diverse learners—at any stage of their life and career—for transformative educational experiences. Across seven schools and colleges, our leading faculty inspires and works alongside students to solve complex challenges and produce impactful, creative work. As part of the state’s largest university system, CU Denver is a major contributor to the Colorado economy, with 2,000 employees and an annual economic impact of $800 million. To learn more about how CU Denver helps learners meet their moment, visit ucdenver.edu.

About Clue

Clue is the top women-led menstrual and reproductive health app, loved by over 10 million users around the world. With a science-driven approach, Clue enables members to create a powerful personal health record that uses each cycle as a tool to uncover insight into their overall health. From general cycle health education to fertility, pregnancy, menopausal stages, and all changes and choices in between, the Clue app is CE-marked as a Class 1 medical-grade device. Clue regularly partners with researchers from top institutions and universities to help close the data gap and move female health forward. Based in Berlin, Germany, Clue data is protected by the world's strictest data laws (the EU's GDPR) and by Clue's absolute commitment to standing up for the privacy of its users, no matter where they are. For more, visit helloclue.com.

About MIT Senseable City Lab

The mission of the Senseable City Laboratory—a research initiative at the Massachusetts Institute of Technology—is to anticipate these changes and study them from a critical point of view. Not bound by the methodologies of a single field, the Lab is characterized by an omni-disciplinary approach: it speaks the language of designers, planners, engineers, physicists, biologists and social scientists. For more, visit https://senseable.mit.edu/

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