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As analytical techniques become more sophisticated,  it is possible to detect an increasing number of chemicals, both natural and synthetic, in our food even at very low concentrations. However this information is not necessarily helpful unless we understand how harmful or harmless these substances are. To compensate for the lack of toxicological data for these newly identified substances, a system for assessing potential toxicity of a substance has been developed - the Threshold of Toxicological Concern (TTC). This system allows priorities to be set for the evaluation of chemical substances.

 

 

For most chemicals there is a level below which a person will experience no adverse health effects. This is because the human body has mechanisms to rapidly get rid of most unwanted substances and repair damage to cells and tissues. However if a chemical is consumed at levels where the body can no longer cope, adverse health effects can develop. The TTC uses this concept to identify a threshold of exposure for chemicals of known structure, below which there is no appreciable risk to human health.

 

Toxicity testing

 

Nowadays, full toxicity assessment of a particular chemical is extensive. It may involve long and short term exposure studies, testing the effects on many systems of the body (such as the nervous, immune and reproductive systems). Any impact on growth and development must be considered, as well as the potential of a substance to damage DNA or to cause cancer. Extensive toxicological data are available for many chemicals, but for new or less well known chemicals, data may not exist and this is where the TTC can help.

 

 

The reason why the TTC is possible is because chemicals with a similar structure that belong to the same family category, exhibit a similar level of toxicity in the body. In other words, they become toxic at around the same level of intake. Extensive analyses of toxicity databases have revealed that there are three broad categories of chemical structural classes which have been found to be of low, moderate or high toxicity. This means that for each category of chemicals it is possible to calculate a generic threshold of toxicological concern, below which there is no appreciable risk to health. This exposure threshold is called the TTC.

 

 

            

The TTC is useful for assessing substances of known chemical structure that are present in foods in low concentrations and for which toxicity data are lacking. This might occur if the presence of a new food contaminant is discovered. The type of substances that might be investigated include: natural contaminants from soil and fungi, substances from food production and packaging, and substances produced during cooking or other means of processing.

 

To use the TTC, a reliable assessment of intake of the chemical must be possible. The level of intake is then compared with the appropriate threshold of toxicological concern and a decision can be made on whether or not further toxicological investigations are needed. With this approach, appropriate resources can be dedicated to a particular chemical, that will be in proportion to the risk to human health.

 

 

The TTC approach is an important tool for risk assessors, risk managers and  industry. Procedures using similar concepts to the TTC are already being used by regulatory bodies such as the European Food Safety Authority (EFSA) and the Joint FAO/WHO Expert Committee on Food Additives (JECFA) for the assessment of flavourings and the US Food and Drug Administration (for flavourings and packaging). The TTC concept has been developed and refined over the last ten years based on extensive scientific research. With more sophisticated analytical techniques, which push the limits of detection even further, the TTC is an efficient and effective approach for assessing potential toxicity, to ensure our foods remain safe. Low exposures to new chemicals can be assessed quickly, and effort can be focused where it is most needed and unnecessary toxicological tests (including those on live animals) can be avoided.