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The threat of Toombak in Sudan

TResearch Spring 2022

Toombak is produced by fermenting the leaves of the Nicotiana rustica tobacco plant

Researchers from Ireland and Sudan have partnered up to shed light on the health implications of one of the world’s most perilous types of smokeless tobacco.

Toombak is a type of popular smokeless tobacco sold by local vendors in Sudan. Most commonly used by men, it’s placed inside the mouth using the fingertips and replaced up to several times a day. Whilst it’s never swallowed, the long-term use of Toombak can lead to many serious and life-threatening issues, such as gum disease, oral cancer, cardiovascular disease, prostate cancer and infertility.

Toombak is produced by fermenting the leaves of the Nicotiana rustica tobacco plant, in a process that can take months.  Nicotiana rustica is used because of its rich nicotine content, and numerous additives are added along the way. Sudanese people have found a way to increase the kick even more by adding sodium bicarbonate to the mix.

Sodium bicarbonate creates an alkaline environment that allows for high absorption rates of nicotine through the mouth lining. This makes the habit extremely addictive, and users find it exceedingly difficult – if not impossible – to quit.

Over the last three years, researchers from Teagasc, research centre APC Microbiome Ireland – based in University College Cork (UCC) – and National Ribat University Sudan have come together to explore in more detail the chemical and microbial (microorganism characteristic) composition of Toombak and its health implications.

The danger within

The researchers used ready-to-buy samples of Toombak from different markets in Khartoum, the capital of Sudan, for their analysis. They were looking at structure, composition and microbiome, as well as looking for heavy metals.

Using a scanning electron microscope, they identified plant fibres of Toombak that were rough with visible bacteria. The heavy metal content was then analysed, showing Toombak has considerable amounts of chromium, cobalt and copper. It also revealed that through daily use, users are exposed to between six and fourteen times more iron than the accepted daily level. 

GothiaTek, an industrial standard, is adopted by members of trade organisation European Smokeless Tobacco Council (ESTOC) to regulate and maintain safe limits of metabolites and other products found in smokeless tobacco in Europe. Following this standard, the researchers found unacceptable levels of toxic metabolites in Toombak.

They also found tobacco-specific nitrosamines (TSNAs), carcinogens that are produced when mushed-up tobacco leaves are left to ferment under intense heat. Not only were TSNAs present in Toombak, but it was found to have the highest content of them in the world when compared to other smokeless tobaccos. TSNAs are one of the main causes of harm from Toombak use, and it is likely that Toombak users are exposed to considerable risk due to its high concentration levels.

When looking at the microbiome of Toombak, the researchers found a number of different groups of bacteria, including bacteria common to chickens, midges, mobile phones and ear infections.

Exploring ways to make Toombak safer

Interestingly, Toombak is a product of fermentation and contains live bacteria on use, but it isn’t healthy in any way. It requires stringent re-evaluation at production and systems levels, in order to reduce the risks associated with it. Smokeless tobacco in Europe and the USA, for example, is pasteurised and packed under sterile conditions in factories, but this is not the case for Sudanese Toombak.

The researchers have established a promising partnership with Esther Health Alliance Ireland to improve microbiome science in Sudan by investing in science, infrastructure and health through microbiome research.

The researchers’ study of Toombak sets out a pathway to better understand different areas of Sudanese life and how these can have both positive and negative impacts on societal health. They have successfully shed light on an important cultural aspect of Sudanese life, and through continuing research, hope to bring about necessary changes for optimum health when producing and using Toombak.  

TResearch Spring 2022

Toombak final product

TResearch Spring 2022

The scanning electron microscope highlighted irregular particles and contamination in Toombak

Toombak in numbers

4 to 10 million

Between 4 to 10 million people use Toombak in Sudan.


Users are exposed to an average of 114.3mg of daily iron from Toombak use, far surpassing the accepted daily level of around 8 to 18mg.


There were 3,210 times more tobacco-specific nitrosamines in Toombak compared to the GothiaTek standard limits.


The metabolite Acetaldehyde was found to be 36 times higher in Toombak compared to the GothiaTek standard limits.


Amel Sami

PhD Student

APC Microbiome Ireland,
UCC and Teagasc.

Imad Elimairi

Immediate past Dean of Dentistry; Professor of Oral and Maxillofacial Surgery 

National Ribat University, Sudan.

R Paul Ross


APC Microbiome Ireland, UCC.

Catherine Stanton

Senior Principal Research Officer

Teagasc Food Research Centre, Moorepark.