One of the world's most common artificial sweeteners is set to be declared a possible carcinogen next month by a leading global health body, according to two sources with knowledge of the process, pitting it against the food industry and regulators.

Aspartame, used in products from Coca-Cola diet sodas to Mars' Extra chewing gum and some Snapple drinks, will be listed in July as "possibly carcinogenic to humans" for the first time by the International Agency for Research on Cancer (IARC), the World Health Organization's (WHO) cancer research arm, the sources told Reuters.

The IARC ruling, finalized earlier this month after a meeting of the group's external experts, is intended to assess whether something is a potential hazard or not, based on all the published evidence.

It does not take into account how much of a product a person can safely consume. This advice for individuals comes from a separate WHO expert committee on food additives, known as the Joint WHO and Food and Agriculture Organization's Expert Committee on Food Additives (JECFA), alongside determinations from national regulators.

However, similar IARC rulings in the past for different substances have raised concerns among consumers about their use, led to lawsuits, and pressured manufacturers to recreate recipes and swap to alternatives. That has led to criticism that the IARC's assessments can be confusing to the public.

JECFA, the WHO committee on additives, is also reviewing aspartame use this year. Its meeting began at the end of June and it is due to announce its findings on the same day that the IARC makes public its decision – on July 14.

Since 1981, JECFA has said aspartame is safe to consume within accepted daily limits. For example, an adult weighing 60 kg would have to drink between 12 and 36 cans of diet soda – depending on the amount of aspartame in the beverage – every day to be at risk. Its view has been widely shared by national regulators, including in the United States and Europe.

An IARC spokesperson said both the IARC and JECFA committees' findings were confidential until July, but added they were "complementary," with IARC's conclusion representing "the first fundamental step to understand carcinogenicity." The additives committee "conducts risk assessment, which determines the probability of a specific type of harm (e.g. cancer) to occur under certain conditions and levels of exposure."

However, industry and regulators fear that holding both processes at around the same time could be confusing, according to letters from U.S. and Japanese regulators seen by Reuters.

"We kindly ask both bodies to coordinate their efforts in reviewing aspartame to avoid any confusion or concerns among the public," Nozomi Tomita, an official from Japan's Ministry of Health, Labour and Welfare, wrote in a letter dated March 27 to WHO's deputy director general, Zsuzsanna Jakab.

The letter also called for the conclusions of both bodies to be released on the same day.