Drinking very hot beverages is "probably carcinogenic to humans," according to a new pronouncement from the International Agency for Research on Cancer (IACR). But there is no danger from drinks that "are not very hot," the agency said.

The new evaluation was carried out by a working group of 23 scientists. The findings were published as an IACR monograph and were published online in the Lancet Oncology.

"These results suggest that drinking very hot beverages is one probable cause of esophageal cancer and that it is the temperature, rather than the drinks themselves, that appears to be responsible," says Dr Christopher Wild, director of the IARC.

The IACR has classified drinking hot beverages as probably carcinogenic to humans (group 2A).

"This was based on limited evidence from epidemiological studies that showed positive associations between cancer of the esophagus and drinking very hot beverages," the agency explained. "Studies in places such as China, the Islamic Republic of Iran, Turkey, and South America, where tea or mate is traditionally drunk very hot (at about 70° C), found that the risk of oesophageal cancer increased with the temperature at which the beverage was drunk."

The agency said that it found no evidence of a cancer risk from drinking coffee and mate (a herbal drink popular in South America).

This latest announcement on coffee is a turnaround from previous findings. In 1991, the IACR classified coffee drinking as possibly carcinogenic to humans (group 2B). But after reviewing new evidence, the group found inadequate evidence and concluded that drinking coffee was not classifiable as to its carcinogenicity to humans (group 3).

The agency noted that many epidemiologic studies have found no increase in risk for many different cancers through coffee drinking. Indeed, some studies have shown a reduced risk for cancers of the liver and uterine endometrium.

The IACR, which is part of the World Health Organisation, regularly assesses the risk for cancer in humans for many different agents. Last year, the agency made pronouncements on meat. At that time, it classified the consumption of processed meat as "carcinogenic to humans" (group 1) on the basis of sufficient evidence for colorectal cancer and a positive association with stomach cancer. The agency also classified the consumption of red meat as being "probably carcinogenic to humans" (group 2A), because an association was observed mainly for colorectal cancer but also for pancreatic cancer and prostate cancer.