The Swiss born physician Philippus Aureolus Theophrastus Bombastus von Hohenheim, quoted as Paracelsus, was the first person to define the founding basis of toxicology with his famous statement “all substances are toxins, there is none that is not a toxin, it is only the dosage that differentiates between the therapeutic and toxic properties of a substance.” This philosophy of his emanated from his defence of using some inorganic substances as medicines while his peers regarded them as too toxic for human beings. The Latin phrase Sola dosis facit venenum says it all: only the dose makes the poison. Yet, in the modern day and age where science is developing as fast as the universe is expanding, society and scientists ignore this base principle of toxicology, especially those in the field of food safety.

Chemicals can be classified as of natural or synthetic origin, the latter mostly being frowned upon by society who seems to forget that the 21st Century is a world of synthetic chemistry: it propels our vehicles (we synthesise a large portion of hydrocarbon fuels such as by SASOL), it flavours our foods, dollies up our own body odours, gives colour to bland faces, protects our skins against solar UV radiation, cleans our laundry and crockery and keeps us healthy as we swallow millions of kilograms of synthetic pharmaceuticals. Oh, not to forget that it keeps our crops, livestock, poultry, and pets free from pests, diseases, and weeds. The synthetic chemicals also give us the convenience of clothes (nylon, Dacron, and polyester) and packaging (plastics). The natural chemicals are all around us as minerals mined and extracted for a multitude or purposes, gases breathed by billions of creatures to stay alive, metabolites extracted from plants as natural medicines, stimulants, narcotics (!) and as of late, as natural pesticides. Many of the synthetic pharmaceuticals and pesticides in the world are derived from natural plant or animal secondary metabolites, such as the pyrethroids that are synthesised from the base molecule pyrethrin.

Fact is that all the chemicals we know of, can be used to the benefit of humanity or at the expense of humanity or other living organisms, but the differentiating factor lies in the wise words of Paracelsus, namely the dose-related response of an organism to a chemical. Second fact is that every chemical is intrinsically hazardous to some species, whether from the Plant kingdom, Animal kingdom or any of the other three namely the Fungi, Protista or Monera kingdoms (these are the base kingdoms of which the Monera can be split into others). This also points to a clarification that no chemical can ever be classified as “safe” in the strict sense of the word. Safe for what? It may cause no harm to people, but it can be extremely toxic to a bee or a fish, for example.

Any chemical, of whatever nature, may pose a risk to a live organism of whatever species, if such an organism is exposed to that particular chemical. Exposure may mean oral intake, dermal contact (and uptake) or inhalation. The question is whether risk is an intrinsic factor of a chemical or not? The answer is simple: No! Risk is a manifestation of the hazard when an organism is exposed to a chemical at a dosage that will elicit a response in the organism. Hazard and risk may be explained in terms of other commodities: every home has a kitchen with knives. Knives are hazardous objects but while kept in their drawers in the kitchen, they pose no risk whatsoever to homeowners. While preparing food with sharp knives, there is a risk: a careful chef will use them with respect and skill, hence the risk of sustaining injuries is low. The learner chef who is not accustomed to the very sharp edges of these objects stand a greater risk of personal injury. When a child gets hold of such a sharp knife, the risk escalates logarithmically. Same with chemicals: a careful and responsible person can use a highly hazardous chemical such as caustic soda (sodium hydroxide) with an exceptionally low risk of harm to themself, while a reckless person who fails to wear gloves and other protective gear while using caustic soda, is at risk of severe injury if any exposed body parts come into contact with the substance. There is also something else to consider, namely acute versus chronic risk. This is where an organism is exposed over a short period of time to a high dose of a chemical, referred to as an acute risk, whereas a very low dosage exposure over extended periods of time is a chronic risk. There is no such parallel for hazard. What is often of concern for toxicologists is the long-term exposure risks where an organism is in contact with very small quantities of a chemical over an extended period. Think of acetyl salicylic acid or aspirin: a single intake of five grams is hardly of concern (unless the patient has some chronic health problems such as gastric or peptic ulcers), but two grams per day taken every day, spells a high risk for severe renal toxidrome (toxic symptoms) in the long term and corrosion of the stomach lining.

Very few people understand the difference between risk and hazard, yet the current trends of understanding and evaluating chemicals by authorities and regulators, are completely hazard based. Chemicals are classified into categories based on their hazard, amongst others acute and chronic oral toxicity, carcinogenicity, mutagenicity, teratogenicity (causing birth defects), and endocrine disruption potential. While acute and chronic oral toxicity values for chemicals is quite uniform across various studies, the carcinogenicity, mutagenicity, and teratogenicity are often disputed between different schools of thought, and endocrine disruption classification is at best quite a clouded piece of science.

In the field of pesticides, the Globally Harmonised System (GHS) of the classification of hazardous substances has taken a stronghold in decision making and regulation of pesticides. The reclassification of pesticides from the WHO based acute toxicological system to a GHS classification system is a good one as it takes the broader hazard potential of a hazardous substance into account. In the WHO classification system, the focus was on hazard to human health, while the GHS system also brings the environment into account. The problem lies in the principles and the understanding thereof. GHS classification does not mean because a substance is classified as hazardous, its use must be terminated; it merely serves as a better tool to classify hazards of substances and alerts the handler/user of such substances to the hazard qualities of the substance. Take diesel fuel for example. It is classified as DANGER according to the GHS system with indications that it is flammable, harmful if inhaled, may be fatal if swallowed and causes skin irritation. There are a few other hazard qualities also listed for diesel. Question is thus: do we terminate the production and use of diesel fuel? Answer this question yourself.

When it comes to pesticides, the nightmare of GHS classification is drawing the curtain on the future of many synthetic and natural pesticide molecules because of hazard qualities. Acute toxicity has always been the basis of the WHO classification, but now chronic effects as mentioned above come into play, plus the environmental angle plays a strong role in the GHS classification. The challenge I see as a toxicologist is that there is no risk-based assessment done to decide whether a pesticide must stay or be terminated. The European Union has systematically degraded the suite of pesticides to something that leaves little room for sensibility. Substances that are highly toxic are eliminated, substances that pose chronic health hazards are eliminated and the list of available chemistry is shrinking rapidly. Make no mistake: some pesticides simply do not have a place in society due to the severe risks they pose, even if used responsibly, but to label a pesticide as unacceptable because it showed chronic health effects in a laboratory rat (that is seldom dosed with a practical dosage) is senseless.

Let me make this debate strongly controversial. If anyone ever reads the insert of a schedule 4, 5 or 6 medicine that is prescribed by a physician to cure an ailment or disease, no sensible person will take such medicine. The risks are well described with studies conducted and presented in a print that is so fine that the reader needs a microscope to decipher the warnings and precautions. A very large percentage of these medicines claim that it is not safe for pregnant women and children, yet it is prescribed and taken by patients. Why are such chemicals still available on the market? Answer this question yourself (my second one to you). Open a kitchen cupboard and find the ammonia, caustic soda, borax, and a host of other hazardous substances on the shelves. Yet, no attempt from the regulators to terminate the manufacture, sales, and use of such chemicals.

The cancer debate is one that speaks of total hypocrisy. Some substances such as benomyl (a fungicide) and glyphosate (a herbicide) have been categorised as carcinogens although this debate is still not concluded. Countless calls for banning glyphosate have been flying around the world, despite the US EPA and the European Food Safety Association both having stated unequivocally that glyphosate is not a human carcinogen. The question is certainly whether a laboratory animal that is forcefully subjected to high exposure levels of a suspected carcinogen is a model for human health? My answer is simply no. It is not. Human beings ingest such a vast array of toxins daily that a few milligrams of something that is not proven to be a carcinogen, cannot have an influence. We live (the urbanites at least) in a world that is ridden with air pollutants from the exhaust fumes of carbon fuel-based engines. Nitrogen oxides, dibenzofurans, sulphur oxides and incompletely combusted hydrocarbons lace the air around us with toxins that people inhale. Exhaust fumes from combustion engines are labelled as definite human carcinogens. Why don’t we ban cars. Well, there is a strong move to electric cars, but how do we charge their batteries? With electricity generated by coal fired power stations that emit toxic fumes and greenhouse gases in millions of tonnes. Hopefully, South Africans will not be coaxed into switching to electric cars because our national electricity supplier is not geared to charge the batteries of such cars.

Let me be even more controversial by questioning the consumption of alcoholic beverages and smoking of tobacco products, both of which have been categorised by the International Association for Research on Cancer as Category 1 carcinogens, meaning they are human carcinogens. So why do we allow the consumption of millions of litres of alcohol every day which is a human carcinogen and a teratogen? Why have alcoholic beverages not been prohibited globally? Is it because the glamorous functions of the WHO and other world authorities will be quite subdued if no alcoholic drinks are served, or is it because it is part of agriculture, part of humanity, and a solid tax generator for governments? Same could be asked of tobacco products. As of more recent is the global legalisation of Cannabis smoking in many countries. As a toxicologist, I am dumbfounded by this sheer stupidity of humankind. You do not want a milligram pesticide in your Greek salad but you wanna smoke pot bro? Hey man, think again.

In 35 years of working against wildlife poisoning, I think I have seen the worst possible cases one can think of. Wildlife, dogs, livestock, and people falling prey to either deliberate poisoning or irresponsible use of pesticides. Yet, one must ask the question (no answer required this time), how we are supposed to control the tough creatures like nematodes without toxic pesticides? Take away the compounds such as terbufos, cadusafos, carbofuran, furfural, etcetera and the farmer is stunted. There are no “soft” alternatives currently, and the future looks bleak because fewer and fewer new pesticides are coming to the fore. One clearly understands the hazards of such pesticides, but the question is whether they pose a risk if they are used responsibly: risk to the consumer who buys and eats the foodstuffs that were produced using such chemicals, risk to workers operating with such chemicals and wildlife that live in areas where such chemicals are applied. If the pesticides are used strictly according to label instructions, I maintain that the risks are manageable, if any at all. However, the risks escalate if the label directions are not adhered to.

Have you ever seen a fuel attendant wearing a respirator mask while filling the tank with petrol or diesel? Have you ever been warned by the waitron that the 2012 vintage merlot wine is a cancer risk to you? Have you ever been warned that oysters contain risky levels of arsenic and other toxins? Have you ever read the entire insert in medicine container? If your answer is no to any of those questions, then why do you insist on food that is produced without chemical pesticides? Why do you treat your dog with a piece of chocolate that contains theobromine that is toxic to dogs? Why do you allow your children to eat crisps that are high in salt and monosodium glutamate? What do think will happen if we apply the GHS classification to all these commodities? When last have you walked past a nail salon and experienced the fumes of toxic substances that pour out the doors? Yet, there are no GHS, respirator masks or warnings in and around them.

The world needs to start thinking and being pragmatic about chemistry. Sure, if we feed a person a tablespoon of pyraclostrobin every day, it is not going to be good for them, but a milligram on an orange peel that is seldomly consumed should not be your concern. Rather switch the car’s engine off.