Carcinogen Report: Weed Killer
and Hot Beverages

The weed killer glyphosate, commonly known by the brand name Roundup,  is not likely to cause cancer in humans through dietary exposure, according to a joint report on pesticide residues from the Food and Agriculture Organization of the United Nations (FAO) and the World Health Organization (WHO). The report also notes that glyphosate is unlikely to damage genetic information in cells, which can cause mutations that lead to certain cancers. This is in contrast to another WHO committee report in 2015 stating that glyphosate was probably carcinogenic.

The groups also concluded that the insecticides diazinon and malathion are unlikely to be carcinogenic through dietary exposure.

Since Roundup is frequently used on crops, the public has been concerned for some time about whether ingesting trace amounts can be harmful to humans. The report states, "In view of the absence of carcinogenic potential in rodents at human-relevant doses and the absence of genotoxicity by the oral route in mammals, and considering the epidemiological evidence from occupational exposures, the meeting concluded that glyphosate is unlikely to pose a carcinogenic risk to humans from exposure through the diet."

An acceptable daily intake of glyphosate, the two groups reaffirmed, is up to 1 mg per kg of body weight.

Reuters Health has reported that less than a year prior to the current finding, a different WHO review, then by that group’s International Agency for Research on Cancer (IARC), found that glyphosate was "probably" able to cause cancer in humans, classifying it as a 'Group 2A' carcinogen. Yet the U.S. Environmental Protection Agency first assessed glyphosate in 1986 and has reviewed it several times since then, also has previously concluded that it has "low toxicity for human."

Among the documents released by the FAO/WHO committee was a question-and-answer that countered the notion that their present conclusions contradicted the previous findings by the WHO’s IARC. The Q&A said that the findings were "different, yet complementary," with the IARC assessment focussed on hazard while the current investigation looked at risk. A hazard is something that can cause harm, such as an electric current, working up a ladder, or in this case, chemicals. A risk is the actual chance, high or low, that any hazard will cause someone harm.

Hot Coffee
Meanwhile, the WHO’s IARC has found that drinking very hot beverages most likely causes esophageal cancer. The report does not recommend drinking coffee, tea, soup, or mate—a beverage commonly consumed in China and South America, usually at very high temperatures—hotter than 149 degrees Fahrenheit (65 degrees Celsius).

Writing in The Lancet Oncology, the IARC researchers say that "biological plausibility exists for an association between very hot beverages and cell injury and the sequelae that might lead to cancer."

The group has, however, declared that on the basis of more than 1,000 studies, coffee is "unclassifiable as to its carcinogenicity to humans," which represents a significant change from its 1991 findings that concluded coffee was "possibly carcinogenic."

The trouble is, coffee is very often served at temperatures much higher than 149 degrees. For example, at Coffee Detective, a website devoted to all things coffee—from brewing tips, home brewing product reviews, etc.—one article states that "[c]offee is best served at a temperature between 155ºF and 175ºF (70ºC to 80ºC). Most people prefer it towards the higher end, at about 175ºF.” In fact, a pre-lawsuit McDonald’s employee manual once recommended that coffee be served at "195 to 205 degrees and held at 180 to 190 degrees for optimal taste."

Coffee Detective goes on to say that "some coffee experts" prefer to drink their coffee at much lower temperatures: “George Howell of George Howell Coffee, who has been sourcing and tasting specialty coffee since the 1970s, likes to drink his coffee at a temperature closer to 130ºF.” It is at this much lower temperature that the more subtle flavors of coffee are apparently truly revealed.

It’s worth noting that the temperature at which coffee is served is not the same as that at which it is eventually drunk; time and milk or cream obviously contribute to temperature-lowering. But since beverages consumed at, say, 140 degrees are likely safe, why not go with the experts and enjoy a more tepid brew, with all of its flavor subtleties intact?

FAO/WHO, Meeting on Pesticide Residues, May 2016,

The Lancet Oncology, Pub. Online June 2016,

Coffee Detective, “What is the correct temperature for serving coffee?”

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