Microplastics: A Rising Concern in Early-Onset Colorectal Cancer

While young adults today tend to live healthier lifestyles—exercising more, eating better, and drinking less—rates of early-onset colorectal cancer are steadily climbing among individuals under 50. Despite overall declines in colorectal cancer cases, approximately 70% of these early-onset cases are deemed sporadic, meaning they are unrelated to inherited genetic conditions or chronic inflammatory issues, such as Crohn’s disease or ulcerative colitis.  

Researchers suspect environmental factors could be driving the rise in colorectal cancer among young adults, with microplastics emerging as a potential culprit. These tiny plastic particles, originating from daily items like kitchenware, clothing, and toys, enter the body via inhalation, ingestion, or absorption. Microplastics have been detected in blood, brain tissue, lungs, and even breast milk, raising concerns about their potential health impacts.  

The increase in microplastic pollution coincides with the surge in early-onset cancers among adults born after 1950—a period when mass plastic consumption began to skyrocket. The environment now sees between 10 and 40 million tons of plastic pollution annually, a figure projected to double by 2040.  

“There are rising epidemiological correlations between microplastic exposure and cancer,” said Dr. Thejus Jayakrishnan, a gastrointestinal medical oncologist at Dana-Farber Cancer Institute. “Laboratory studies show plastic may have carcinogenic effects, but much remains to be understood.”  

Potential Pathways for Microplastics to Trigger Cancer  

The gut is equipped with a protective mucus lining that traps and guards against foreign particles and bacteria. This layer is crucial for preventing toxins—often produced by certain foods such as alcohol, red meat, and processed meals—from damaging intestinal walls.  

Professor Frank Frizelle, a colorectal surgery specialist at the University of Otago in New Zealand, explained that while it traditionally takes decades for toxins to cause enough damage to spur cancer, microplastics might accelerate the process by disrupting the gut lining.  

Frizelle hypothesizes that microplastics act as a "dead weight" on the mucosa, penetrating its protective layers and enabling harmful toxins to bypass the barrier. “Think of it as creating tiny pinpricks in a condom—damaging the protective mechanism and letting harmful substances through,” Frizelle said.  

Alternatively, microplastics might attach to fat molecules in the hydrophobic mucosal lining or interfere with tight junctions—the bonds between intestinal cells that help regulate nutrient absorption and protect against toxins. Research shows smaller particles, like nanoplastics, may have even greater potential to disrupt cell structures and cause harm.  

Impact on the Gut Microbiome  

Microplastics may also weaken the gut microbiome, a diverse ecosystem of beneficial and harmful bacteria. A healthy microbiome relies on prebiotic fiber to nourish protective microbes. However, harmful bacteria or insufficient dietary fiber may cause bacteria to degrade the mucosal lining, increasing inflammation and creating a favorable environment for cancer development.  

Certain bacteria, including Fusobacterium nucleatum and E. coli, are known to contribute to colorectal cancer growth. Chronic inflammation caused by dysbiosis—or an imbalance in gut bacteria—has long been linked to cancer.  

Researchers are also exploring whether microplastics carry harmful bacteria into the gut. Microplastics found in the ocean have been shown to harbor microorganism communities, including pathogenic bacteria, suggesting that ingested plastics could similarly transport cancer-causing microbes in the body.  

“Microplastics are often mixed with added chemicals that can be carcinogenic, such as PFAS or ‘forever chemicals,’” noted Dr. Somdat Mahabir, program director in the Environmental Epidemiology Branch of the National Cancer Institute. These additives may disrupt microbiome balance, damage DNA, or directly contribute to cell mutations, further amplifying their harmful effects.  

Moving Forward with Research  

Understanding how microplastics contribute to colorectal cancer requires further investigation. Researchers currently face challenges in establishing causation due to the widespread presence of plastics in the environment, leaving few opportunities to compare exposed and unexposed populations.  

Dr. Jayakrishnan’s team gathers stool, blood, and biopsy samples from cancer patients to study microplastic concentrations and interactions within the body. This research aims to identify biomarkers or genetic indicators that suggest increased cancer risk, potentially enabling earlier intervention or prevention measures.  

Meanwhile, Frizelle’s team uses tissue samples and animal models to study how plastics affect the gut lining. Future progress will depend on verifying hypotheses about microplastic disruption and translating findings into larger-scale studies.  

“This has been a lot of trial and error—20 failures to every success,” Frizelle said.  

Frizelle likened public awareness of microplastic risks to early revelations about smoking and lung cancer. Plastics have only recently come under scrutiny for their potential carcinogenic effects, despite decades of increasing environmental exposure.  

“This is new stuff,” he said. “I think we’re underestimating the damage microplastics are causing. Like putting sand in an engine, they’re likely doing far more harm than we currently perceive.”  

Ongoing research into microplastics may open new doors for understanding and mitigating early-onset colorectal cancer—and perhaps broader health implications of plastic pollution. Scientists remain committed to uncovering the mechanisms driving this alarming trend and paving the way for more targeted prevention and treatment strategies.