This picture taken on October 9, 2021 shows a member of the bar staff preparing kratom-infused mocktails at the Teens of Thailand cocktail bar in Bangkok. ( AFP / Jack TAYLOR)

Posts misleadingly claim 'formalin in ice cubes causes cancer in Thailand'

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Social media posts claim Thailand has the "highest number of cancer patients in the world" because the kingdom's citizens use ice cubes that contain the chemical formalin, and they consume chlorinated water. But Thai health experts rubbished the claim, saying there was no evidence that formalin was being added to ice cubes, or that the controlled amount of chlorine used to disinfect tap water can cause cancer. Thailand also does not have the highest number of cancer patients in the world, according to data collected by the World Health Organization (WHO).  

The claim was shared in a Facebook post on February 5, 2022.

The Thai-language caption reads in part: "I just found out ice cubes have 'formalin' added in to prevent melting. They said formalin will slow the melting. When we wake up, we drink water that has chlorine in it. That's why Thailand has the highest number of cancer patients in the world."

Screenshot of the misleading post, captured on February 10, 2022

It also claims "foreigners in Phuket don't eat ice cubes because they know about this".

Formalin is the liquid form of formaldehyde, which is a strong-smelling, colourless gas. It is used as an industrial disinfectant and as a preservative in funeral parlours and medical labs, and also in some foods and medicines.

Studies of workers exposed to high concentrations of formaldehyde have found links to some types of cancer.

The chemical element chlorine can be used in small amounts to disinfect drinking water and swimming pools.

Similar claims have been shared here and here on Facebook and here on Twitter. 

Some social media users' comments indicate they believed consuming ice led to Thailand's "high cancer rate".

One said: "Don't eat ice cubes!", while another wrote: "I don't like to eat ice cubes, guess I am going to survive."

However, the claims are misleading.

Formalin claim

Tirayut Vilaivan, a professor at Chulalongkorn University's Department of Chemistry told AFP on February 9 there is no evidence to support the claim in the misleading posts.

"There is no formalin added in ice cubes because it wouldn't change anything in the ice cubes," he said. 

"This is an old hoax that has been shared for years."

He said the melting of ice "could not be prevented by any chemical solutions".

It was also "scientifically impossible to eat" ice cubes if they contained formalin because the chemical has a strong smell and taste, he added.

Dr Sakarn Bunnag, the director of Thailand's National Cancer Institute also refuted the claim.

"It has a very pungent smell. Even a small amount can irritate your nose and eyes," he told AFP on February 10, 2022.

Experts also said there is no evidence that chlorine in tap water can cause cancer.

Tirayut said: "Chlorine is used to disinfect tap water and is part of the sanitisation process anywhere in the world. However, the amount added is controlled and is safe for humans." 

Thailand's cancer cases

Thailand does not have the highest number of cancer patients in the world, latest data collected by international health bodies shows.

According to the latest report from WHO-led research centre Global Cancer Observatory, China, the United States and India topped the estimated number of new cases in 2020, while Australia, Ireland, and New Zealand topped the global index for age-standardised rates (ASR) in estimated new cancer cases. Age standardisation is a technique that allows statistical populations to be compared when the age profiles of the populations are different. 

Thailand ranked 19th on the number of cases and 88th on the global index for age-standardised rates.

February 14, 2022 This article was updated to correct Thailand's ranking on the global index in the last paragraph.