The IARC classified this as a possible carcinogen in their category 2b based on limited evidence of a particular cancer in humans — hepatocellular carcinoma, which is a type of liver cancer. The strength-of-evidence classification in Group 2B is the third highest level out of 4 levels, and it is generally used either when there is limited, but not convincing, evidence for cancer in humans or convincing evidence for cancer in experimental animals, but not both. This classification is primarily intended to inform researchers to encourage further research of aspartame, and it does not make any assertion about the relative risk associated with typical exposure levels. It rather determines whether the substance could be carcinogenic at any dose — even if the required dose far exceeds typical exposure.

Notably, JEFCA, the group responsible for researching and making recommendations on food additives, reviewed the same evidence as the WHO and concluded that the data evaluated indicated no sufficient reason to change the previously established acceptable daily intake (ADI) of 0–40 mg/kg body weight for aspartame. The committee therefore reaffirmed that it is safe for a person to consume within this limit per day. For example, with a can of diet soft drink containing 200 or 300 mg of aspartame, an adult weighing 70kg would need to consume more than 9–14 cans per day to exceed the acceptable daily intake, assuming no other intake from other food sources.

https://www.who.int/news/item/14-07-2023-aspartame-hazard-and-risk-assessment-results-released