How Science is Fighting Back Against Environmental Risk Factors
When we think about breast cancer risk, we often focus on family history and genetics. But what if the environment around us—the air we breathe, the chemicals in everyday products, and the water we drink—also plays a crucial role?
Less than 10% of breast cancer cases are linked solely to family history 2 , challenging the common perception that genetics is the primary determinant.
Groundbreaking research reveals that environmental exposures account for a substantial portion of breast cancer cases, opening powerful new avenues for prevention.
Breast carcinogenesis involves multiple genetic and environmental events
Several classes of chemicals pose particular concern for breast cancer risk
Timing of exposure can be as important as the exposure itself
These compounds interfere with the body's hormonal systems. Some EDCs, such as phthalates (found in some plastics and personal care products) and PFAS "forever chemicals" (used in non-stick cookware and food packaging), can mimic estrogen—a known risk factor for breast cancer 2 7 .
Recent Mendelian randomization studies have identified nitrogen dioxide (NO₂) and particulate matter (PM10) as having causal relationships with increased breast cancer risk 1 .
Exposures during fetal development can have lifelong impacts on breast cancer risk, with research suggesting transgenerational effects 5 .
During puberty, breast tissue undergoes rapid development and may be more susceptible to environmental damage 5 .
Pregnancy represents another critical window when breast tissue changes dramatically, potentially increasing vulnerability to environmental factors 5 .
In 2025, a groundbreaking study employed an innovative method called Mendelian randomization (MR) to investigate the relationship between air pollution and breast cancer 1 . This approach uses genetic variants as natural proxies for environmental exposures, helping researchers overcome limitations of traditional observational studies.
Using genetics to uncover environmental causes of disease
Researchers selected genetic variants associated with exposure to four air pollutants from genome-wide association studies of over 400,000 UK Biobank participants 1 .
Breast cancer outcome data came from two large consortia: the Breast Cancer Association Consortium (122,977 cases) and the FinnGen study (20,586 cases) 1 .
The primary analysis used inverse-variance weighted method, supplemented by multiple sensitivity analyses to validate results 1 .
Researchers examined associations with estrogen receptor-positive and negative subtypes, plus breast cancer survival outcomes 1 .
The analysis revealed that specific air pollutants significantly increase breast cancer risk. The most pronounced effects were observed for NO₂ and PM10:
| Pollutant | Risk Increase per SD | Statistical Significance | Subtype Specificity |
|---|---|---|---|
| NO₂ | 68% higher risk | P < 0.05 | All types |
| PM10 | 36% higher risk | P < 0.05 | ER+ and ER- |
| PM2.5 | Not significant | P > 0.05 | - |
| NOx | Not significant | P > 0.05 | - |
The findings demonstrated that the effects of PM10 were consistent across both estrogen receptor-positive and negative subtypes, suggesting multiple mechanisms of action beyond hormonal pathways 1 . Interestingly, no significant associations were observed between air pollution exposure and breast cancer survival, indicating these pollutants may influence cancer initiation rather than progression 1 .
| Aspect | Traditional Observational Study | Mendelian Randomization |
|---|---|---|
| Confounding | Prone to lifestyle confounding | Minimizes confounding through genetic instruments |
| Reverse Causality | Breast cancer could influence exposure reporting | Genetic variants precede disease onset |
| Measurement Error | Relies on self-reported or estimated exposure | Uses genetically-predicted exposure levels |
| Cost | Expensive for long-term exposure assessment | Uses existing genetic data |
Cutting-edge research into environmental causes of breast cancer relies on sophisticated tools and technologies. These reagents and systems enable scientists to model human biology, identify harmful chemicals, and understand mechanisms of action.
Function: Supports the growth of mammary epithelial cells
Application: Models effects of chemicals on normal breast tissue
Function: Identifies and isolates cancer stem cells
Application: Studies how pollutants affect cancer-initiating cells
Function: Analyzes gene expression in individual cells
Application: Reveals how chemical exposures create tumor heterogeneity 9
Function: Maps gene activity within tissue context
Application: Shows how cancer cells interact with their microenvironment after chemical exposure 9
These tools have enabled remarkable discoveries. For instance, single-cell sequencing has revealed how environmental exposures create tumor heterogeneity—where breast tumors consist of diverse cell populations with different genetic profiles that influence treatment response 9 . Meanwhile, liquid biopsies offer a non-invasive method to monitor the early biological effects of environmental exposures by detecting circulating tumor DNA 9 .
The Breast Cancer Prevention Partners (BCPP) successfully campaigned to remove DEHP (a harmful phthalate) from intravenous medical equipment, resulting in both state-level bans and a commitment from Baxter International—the nation's largest IV supplier—to eliminate DEHP from IVs nationwide by 2030 2 .
The 2025 Breast Cancer Prevention Conference featured dedicated sessions on translating scientific evidence into policy, focusing on why current regulations often lag behind scientific evidence and how researchers can effectively influence policy change 5 .
Choosing personal care and cleaning products without endocrine-disrupting chemicals like phthalates and certain PFAS.
Supporting clean air initiatives and being mindful of exposure to traffic-related pollutants, particularly during critical life stages like puberty and pregnancy.
Maintaining a healthy weight, limiting alcohol consumption, and staying physically active—all modifiable factors that may help offset environmental risks 9 .
Effective breast cancer prevention requires action at multiple levels, from individual choices to systemic policy changes.
Lifestyle choices and product selection
Local advocacy and awareness campaigns
Corporate responsibility and safer alternatives
Regulations and environmental protections
The compelling evidence connecting environmental factors to breast cancer risk fundamentally shifts our approach to this disease.
Rather than waiting to treat breast cancer after it develops, we now have the knowledge to prevent a significant proportion of cases by addressing modifiable environmental factors. The scientific community is increasingly united around the principle that prevention is possible, with research initiatives like the BLOOM project and Project TERI focusing on empowering vulnerable communities and addressing environmental justice issues 2 .
"The incidence rates of breast cancer continue to go up but we're not really doing enough to understand what the causes are of that."
While treatment advances continue to improve outcomes for those diagnosed with breast cancer, the most effective and humane approach remains preventing the disease before it starts. By supporting continued research into environmental factors, advocating for evidence-based policies, and making informed individual choices, we can work toward a future with fewer breast cancer diagnoses.
It's time to change the paradigm and build a world where our environment protects rather than threatens our health.