The additive aspartame will be listed as “possibly carcinogenic” by the World Health Organization’s (WHO’s) cancer research branch: the International Agency for Research on Cancer (IARC). According to a report by Reuters, the IARC ruling was finalized in early July after meetings with external experts.

Aspartame is used in a number of products that are advertised as having reduced or no sugar. The additive is stated to be 200 times sweeter than sucrose. The IARC’s analysis of aspartame examined all existing evidence in order to determine whether the additive is likely to be carcinogenic. The IARC has four levels of classification for substances and stimuli: carcinogenic, probably carcinogenic, possibly carcinogenic, and not classifiable.

While the IARC seeks to discover whether a substance can cause cancer, they are not the authority responsible for determining how much of a substance is safe to consume. The agency that will decide how much, if any, aspartame is safe to consume is the Joint WHO and Food and Agriculture Organization’s Expert Committee on Food Additives (JECFA). JECFA has also been evaluating aspartame, with their investigation beginning in June and expected to conclude in mid-July. This is an unusual instance in which the IARC and JECFA are reviewing the same substance simultaneously.

While an IARC spokesperson has said that their analysis of aspartame is "the first fundamental step to understand carcinogenicity," the decision to label the additive as possibly carcinogenic may have far-reaching consequences. Although the IARC has no lawmaking power, its declarations have led manufacturers and corporations to change recipes and swap to alternative ingredients after a declaration that a substance may be carcinogenic. 

Notably, in 2015 the agency rated glyphosate as “probably carcinogenic.” This ruling led to years of lawsuits and clamoring for accountability from the public, with the primary recipient of this crusade of cases being the German company Bayer. 

Because the IARC is chiefly concerned with analyzing whether something is carcinogenic and not how much of it puts people at risk, the agency has been criticized by some for needlessly stirring up concerns where no real problem existed. Among the things the IARC has rated as carcinogenic, probably carcinogenic, or possibly carcinogenic include working overnight shifts, eating red meat, cell phone radiation, and asbestos. These things are not all equally lethal and must be approached on a case-by-case basis. This is why the complementary analysis by JECFA is expected to come on the same day as the IARC announcement, to clarify the real danger that people may or may not be in.