Does Steaming Food Cause Cancer From Chlorine?!

Can you get cancer from chlorine if you steam your food?!

Take a look at the viral claim, and find out what the facts really are!


Claim : Steaming Food Can Cause Cancer From Chlorine!

This advice by a Chinese professor keeps going viral on WhatsApp, and social media platforms:

Please be sure to forward:

Steam food with water
Beijing Xuanwu Hospital Professor Qi’s article:

When steaming food, please be sure to open the lid to boil the water before adding the food to be steamed covered! No wonder more and more people have cancer.

When cooking food with the pot, we must use boiled water. Because if we directly use tap water, which has chlorine, and after heating due to the lid been covered, the chlorine is completely coated on the food. So be sure to use boiled water or filtered water without chlorine to steam thing.

Because chlorine is carcinogenic. This is really important! Even if only steaming buns, we must have this common knowledge.

Please share this info to more people. I hope all my friends are healthy.


用開水蒸東西 ,北京宣武醫院齊教授的文章:蒸食物請一定要先開著蓋子把水燒開,再放入要蒸的食物,蓋上蓋子!難怪患癌症的人愈來愈多。用鍋蒸煮東西時,一定要用開水。因為如果直接用自來水,自來水有氯,再經過加熱後,由於鍋蓋是蓋著的,氯被全部包覆在食物上,所以一定要用煮沸過的開水或用已過濾掉氯的水來蒸東西。因為氯有致癌的危險。這真的很重要!即使只是蒸饅頭,都要有此常識。不要自私,讓更多的人看到。 這個以前真不知道,以後得記住了。希望所有朋友都健健康康,贈人玫瑰 手有餘香

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No Evidence Steaming Food Can Cause Cancer From Chlorine!

This is yet another example of FAKE NEWS circulating on WhatsApp and social media, and here are the reasons why…

Fact #1 : There Is No Chlorine Gas In Tap Water

First, I should point out that tap water does not actually contain chlorine gas. Chlorine gas may be used to disinfect tap water, but it is quickly transformed into other chemicals that actually disinfect the water – hypochlorous acid and hypochlorite anion.

The common usage of chlorine (or free chlorine) in tap water really refers to these chemical compounds, and not chlorine gas itself. There is certainly no chlorine gas inside tap water.

Fact #2 : Regulated Tap Water Has Low Levels Of Chlorine

Tap water in most countries only has low levels of chlorine – between 0.2 to 1 mg per litre, although it may go as high as 4 mg per litre – four parts per million.

Fact #3 : Water With Too Much Chlorine Is Undrinkable

In places where the levels of chlorine in the tap water is poorly regulated, it may be possible for the tap water to have too high levels of chlorine – anything above 4 mg per litre – four parts per million.

Even if you do not have professional testing on hand, you can look out for signs of too much chlorine in the water:

  • the water smells or tastes like swimming pool water
  • you experience nausea, diarrhoea, or vomiting after drinking the water

I should point out that swimming pools have an upper limit of 5 mg per litre – five parts per million, while spas can go as high as 10 mg per litre. You can taste the chlorine in the water, but even then, it is not dangerous to accidentally swallow some of the water, although it is distasteful.

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Fact #4 : Chlorine Evaporates Naturally From Tap Water

What people may not realise is that chlorine is volatile and evaporates naturally from tap water over a day or so.

If you leave a glass of tap water in the open, it should be pretty much chlorine-free after a day or so.

Fact #5 : Chlorine In Tap Water Evaporates When Heated

The vapour pressure of chlorine is much lower than that of water, so it will evaporate by the time your tap water starts boiling.

The evaporated chlorine “escapes” with the steam, and doesn’t coat your food as claimed, because… its vapour pressure is lower than that of water!

So the risk of getting cancer from chlorine is lower, if not eradicated, by steaming or boiling tap water.

Fact #6 : Only Certain Water Filters Can Remove Free Chlorine

The typical particle filters will not remove free chlorine. Only water filters using reverse osmosis and/or active carbon filters can remove free chlorine from tap water.

So the advice to just use filtered water is not accurate, as the filtered water will likely still contain chlorine (unless it uses reverse osmosis / carbon filtration)

Fact #7 : Carcinogenicity Of Chlorine Has Not Been Determined

The International Agency for Research on Cancer (IARC) and the US Environmental Protection Agency (EPA) has not classified chlorine regarding its human carcinogenicity.

That’s likely because chlorine is an irritant, and it is unlikely for humans to willingly consume large amounts of it.

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Fact #8 : Trihalomethanes Are The Real Risk, Not Chlorine

Chlorine may react with organic matter in the water to produce compounds like trihalomethanes, such as chloroform, dibromochloromethane (DBCM), bromodichloromethane (BDCM), and Bromoform.

These trihalomethane compounds are potential human carcinogens. These are the compounds that pose a potential health risk, and not the free chlorine in tap water itself.

However, the level of trihalomethane compounds in well-regulated tap water is very low, so the real risk occurs when there is poor regulation of tap water.

Yan Zonghai, Director of the Clinical Toxicology Department of Chang Gung Hospital in Linkou, said that the public is worried that after chlorine disinfection in tap water, there may be residual “trihalomethanes”, which are volatile organic compounds with low boiling points. Long-term exposure in large quantities may cause cancer.

The World Health Organization (WHO) lists trihalomethanes as a confirmed carcinogenic risk in animals, but there is no relevant evidence for human cancer. Yan Zonghai emphasized that the limit value of chlorination and disinfection of tap water is checked, and the possible production of trihalomethanes is very small, so the public should not worry.

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Dr. Adrian Wong has been writing about tech and science since 1997, even publishing a book with Prentice Hall called Breaking Through The BIOS Barrier (ISBN 978-0131455368) while in medical school.

He continues to devote countless hours every day writing about tech, medicine and science, in his pursuit of facts in a post-truth world.


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