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Social posts claim screenings cause cancer: what the evidence says
A viral post claimed Pap smears, mammograms, and COVID tests cause cancer. Fact-checkers rated it false. Here is what health agencies say.
Original commentary from the Cancer Explained editorial team.
Please note: this page is educational only — it is not medical advice, and it does not speculate about anyone’s health beyond reliable public reporting. For questions about your own health, talk with your healthcare team.
The short answer
Screening tests are designed to find disease early, not to cause it. A post shared widely on X in early September 2026 claimed otherwise. On September 8, 2026, the fact-checking site FactCheckHub rated the claim false.
What the post said
According to FactCheckHub, the post was viewed more than 91,000 times. It claimed that:
- Pap smear tools are sterilized with ethylene oxide, a cancer-causing chemical.
- Mammograms expose breast tissue to harmful radiation.
- COVID tests contain sodium azide.
The post suggested these tests are meant to cause cancer.
What the evidence says
Pap smear tools. Doctors quoted by FactCheckHub said sampling devices are single-use and thrown away after use. The FDA says about half of sterile medical devices in the U.S. are sterilized with ethylene oxide, and that standards limit how much can remain on a device.
Mammograms. The American Cancer Society says a typical screening mammogram gives about 0.4 mSv of radiation, about the same as 1 to 2 months of radiation from normal, everyday life. ACS says the benefits outweigh any possible harm from the radiation.
COVID tests. FactCheckHub cites Poison Control saying nasal swabs do not contain the liquid that may include sodium azide.
What is true
Radiation from imaging is not risk-free. NCI says ionizing radiation raises cancer risk, but the added risk from one CT scan is small, and the benefits of a needed scan greatly outweigh it. Colonoscopy uses no radiation at all.
Read more in our guide: Do routine screenings cause cancer?
If you notice a change in your body that is new or lasts, get it checked. In an emergency, call 911.
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Put the story in context
Prevention, possible warning signs, screening, and diagnosis
This story relates to Cancer screening. The information below is general: it does not reveal anything else about a public person’s health, and not every point applies to every cancer. Personal advice depends on age, symptoms, family history, exposures, and medical history.
Prevention and risk reduction
Not every cancer can be prevented. Avoiding tobacco, protecting skin from ultraviolet radiation, limiting alcohol, staying active, and receiving recommended HPV or hepatitis B vaccination can lower the risk of certain cancers. A risk factor is not a prediction or a cause in one individual.
Symptoms and possible early signs
Possible signs vary and are often caused by conditions other than cancer. Changes worth discussing include a new lump, unexplained bleeding or weight loss, a persistent cough, lasting bowel or bladder changes, a changing skin spot, or symptoms that persist or worsen. Some early cancers cause no symptoms.
Screening and early detection
Screening looks for certain cancers before symptoms begin. Recommended tests exist only for some cancers and depend on age and risk. Screening can have benefits and harms; it is not the same as evaluating a new symptom, and there is no single routine scan or blood test that reliably screens for every cancer.
How cancer is diagnosed
Diagnosis may involve a history and exam, imaging, laboratory tests, and often a biopsy. Pathology can identify the cancer type and may test biomarkers that guide treatment. Symptoms, screening results, tumor markers, or online stories alone cannot confirm cancer.
Learn about this story’s cancer topic
A public story may encourage questions, but it should not be used to estimate your risk or choose testing. Contact a healthcare professional about a persistent or concerning change. Seek urgent care for severe or rapidly worsening symptoms.