One of the most prominent pioneers of the science of toxicology was Paracelsus (1493–1541). He was born in Switzerland and became famous as a lecturer in medicine at the University of Basel. He is often quoted for the famous words, “What is there that is not poison? All things are poison and nothing (is) without poison. Solely the dose determines that a thing is not a poison.” This simply explains that all chemicals can be toxic at a certain dose. This concept can be illustrated by the example of a substance called strychnine. In small amounts, strychnine is a tonic, but in large doses it is poisonous. Another example is water – certain amounts are essential to life, whereas large amounts cause death by drowning. The principle that Paracelsus defined many years ago is still valid today.
Plants and other organisms have been collected for food and medicinal purposes through the ages. Early humans probably learned through experience about the harmful properties of poisonous plants, insects and animals (venom). Domestication of food plants led to reduced levels of natural toxins and allergens. Poisons were used in killing for example in arrows and used maliciously to poison people. However, plants were also used as cures against poisoning. Treatment followed on a rational base only when toxicology became a science and when mechanisms of toxicity were understood.
Toxins and toxicants
Various sources of poisons exist. Those that occur in nature, called toxins, occur as part of the composition of the food plants or animals or as chemical substances in the environment.
They often provide a natural defence mechanism for plants and animals Examples are toxins in certain mushrooms, toxic glycoalkaloids in potatoes, psoralens in celery and parsley, and safrol in nutmeg and cinnamon. Examples of animal toxins are the venom from snakes and spiders, but toxic substances are also present in certain bacteria for example Botulinum neurotoxin. Another source of natural toxic substances are the chemical substances that are present in soil and water, such as cadmium and mercury. However, food could also become contaminated by exposure to fungi during agricultural practices or improper storage of agricultural products. There are a large number of fungal toxins. Examples include the toxin aflatoxin that is produced by the fungus Aspergillus flavus, which contaminates for instance groundnuts, fumonisin toxin in maize, and patulin toxin in apples. These fungal toxins are mostly present in spoiled food, which can enter the food chain, thereby posing a risk to human beings.
Toxicants on the other hand are human-made chemicals such as pesticides, bisphenol in certain plastic products, and millions of other industrial chemicals.
Toxicology is the study of the adverse effects of natural toxins and toxicants on the human or animal body. Toxicology uses the power of science to predict what, and how chemicals may cause harm or become a hazard. The definition of hazard is ‘a biological, chemical or physical agent in, or condition of, food with the potential to cause an adverse health effect’. Basically, toxicology is the science of poisons.
Toxicologists are qualified scientists who have an understanding of many scientific disciplines such as biology, chemistry, and pharmacology. They are specialised in the science and study of toxins and toxic substances. Specialities include clinical toxicology (which specialises in the diagnosis and treatment of toxic symptoms), industrial toxicology (which specialises in poison in an occupational situation), regulatory toxicology (which specialises in regulatory requirements for the toxicological assessment of new chemicals, which could be human or veterinary medicines, and pesticides) and environmental toxicology (which specialises in the toxic effects on the environment).
Toxicological assessments: International expert bodies
Expert committees of international bodies such as the Food and Agricultural Organization (FAO) and the World Health Organization (WHO), as well as many government bodies, are responsible for conducting toxicological assessments of chemicals that are of food safety concern. The Codex Alimentarius Commission is the central part of the Joint FAO/WHO Food Standards Programme. Committees of Codex are responsible for collection of standards, guidelines and codes of practice to be adopted by the Codex Alimentarius Commission. Three international committees are of importance to toxicological assessments: Joint FAO/WHO Meeting on Pesticide Residues (JMPR), JOINT FAO/WHO Expert Committee on Food Additives (JECFA) and Joint FAO/WHO Expert Meetings on Microbiological Risk Assessment (JEMRA). The assessment of microbial food risks is not further explained in this communiqué.
The Organization for Economic Coordination and Development (OECD) is responsible in particular for guidelines for the toxicological assessment of chemicals. The range of tests can be found on the OECD website (www. OECD). These tests are prescribed requirements by many countries as well as assessments by JMPR and JECFA. Countries may have their own methods that are acceptable by the international bodies.
Place of toxicological assessments in risk analysis
To understand the role of toxicological assessment in the greater concept of risk assessment, an explanation of risk analysis in food safe should be given.
An important approach to safety assessment of food is ‘risk analysis’, which consists of three distinct but closely linked components (risk assessment, risk management and risk communication) as defined by the Codex Alimentarius Commission.
How can RISK be described? The simple description is Risk = Factor x Hazard x Exposure. Therefore, risk assessment consists of determining hazard and exposure. In more detail, risk assessment consists of four steps: hazard identification, hazard characterization, exposure assessment and risk characterization. Toxicological assessments form a critical part of hazard identification and characterization. They provide the knowledge to determine what the hazards are and to identify their immediate, interim and long-term effects on human health. These can be described as the doses mentioned by Paracelsus.
Exposure assessment, on the other hand, includes a number of activities that differ from those of toxicity determination, but are a critical part of risk assessment.
The risk analysis process is widely recognized as the fundamental methodology that underlies the development of food safety standards to establish the appropriate measures of control to prevent, reduce or minimize these risks (risk management).
One has to remember that, unfortunately, there is no such thing as ‘zero risk’ for food.
What Is The situation In South Africa?
South Africa has legislation and a regulatory system in place to assess and control the use of toxins and toxicants.
What additional ways are there to improve risk assessment?
At international level, review and refinement of toxicological methods are constantly attended to, to improve the assessment of toxic substances. To improve risk assessment reviews, FAO/WHO requests epidemiological surveillance data and analytical and exposure data from countries. These may not be freely available, particularly from developing countries.
Many life-threatening toxic chemical substances and natural toxins have been identified and governments and international bodies scrutinize new ones carefully. Legislation to ensure the safety of food is stringent. Traditional methods and knowledge about naturally occurring toxins must be communicated to ensure that toxins do not become problematic. Prepared for FACS by WRi (2019)
Food and Agricultural Organization (FAO). Annex 2 – The application of risk analysis to food safety control programmes. Available from http://www.fao.org/docrep/W8088E/w8088e07.htm. Viewed 29 January 2018
Organization for Economic Coordination and Development (OECD). Chemical safety. Available from http://www.oecd.org/chemicalsafety/testing/. Viewed 29 January 2019.
International Programme on Chemical Safety, ILO, UNEP and WHO. (IPCS) (2009). Environmental Health Criteria 240. Principles and methods for the risk assessment of chemicals in food. A joint publication of the Food and Agriculture Organization of the United Nations and the World Health Organization. Available from http://www.inchem.org/documents/ehc/ehc/ehc240_front.pdf Viewed 29 January 2019