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The British Medical Journal study found that drinking steaming hot tea has been linked with an increased risk of oesophageal cancer.
Experts said the finding could explain the increased oesophageal cancer risk in some non-Western populations.
Adding milk, as most tea drinkers in Western countries do, cools the drink enough to eliminate the risk.
Tobacco and alcohol are the main factors linked to the development of oesophageal cancers in Europe and America.
Golestan Province in northern Iran has one of the highest rates of OSCC in the world, but rates of smoking and alcohol consumption are low and women are as likely to have a diagnosis as men. Tea drinking, however, is widespread.
The University of Tehran researchers studied tea drinking habits among 300 people diagnosed with OSCC and compared them with a group of 570 people from the same area.
Nearly all participants drank black tea regularly, on average drinking over a litre a day.
Compared with drinking warm or lukewarm tea (65C or less), drinking hot tea (65-69C) was associated with twice the risk of oesophageal cancer, and drinking very hot tea (70C or more) was associated with an eight-fold increased risk.
The speed with which people drank their tea was also important. There was no association between the amount of tea consumed and risk of cancer.
Drinking a cup of tea in under two minutes straight after it was poured was associated with a five-fold higher risk of cancer compared with drinking tea four or more minutes after being poured.
A large proportion of Golestan inhabitants drink hot tea, so this habit may account for a substantial proportion of the cases of oesophageal cancer in this population.
Previous studies from the UK have reported people prefer their tea to be about 56-60C--cool enough not to be risky.
Oliver Childs, a spokesman for Cancer Research UK, said: "Tea drinking is part of many cultures, and these results certainly don't point to tea itself being the problem."
"But they do provide more evidence that a regular habit of eating and drinking very hot foods and drinks could increase your risk of developing cancer of the oesophagus."
He advised tea-drinkers to simply wait a few minutes for their brew to cool from "scalding" to "tolerable".
