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  "path": "/news/2026-03-human-blood-scientists-dont.html",
  "publishedAt": "2026-03-14T19:30:01.000Z",
  "site": "https://medicalxpress.com",
  "textContent": "Humans evolved in an atmosphere containing roughly 200–300 parts per million (ppm) of carbon dioxide (CO₂). Today, that figure sits above 420 ppm, higher than at any point in the history of our species.",
  "title": "Rising CO₂ levels are reflected in human blood. Scientists don't know what it means"
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