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Food Focus August 2008

Why Mother Nature must be a part of pesticide regulation

As a child you may have been told not to eat the green parts of potatoes because they’d make you sick. Dr Joel Mattsson has had many close encounters with the green side of potatoes. He describes here the toxic nature of the many natural pesticides in our environment

Mother Nature has the capacity to do great good and to do great harm, and ignoring her is not a good strategy to avoid harm. Although we depend on crop foods for good nutrition, all plants have the capacity to harm people because of high levels of plant self-defense chemicals (‘natural pesticides’), food allergens and fungal contaminants. Plants may be stuck in the ground, but they are alive and do not sit there passively when attacked by insects, fungi and other threats. Plants get ‘angry’ and respond to attack by substantially increasing their natural pesticides and some allergens (pathogenesis-response protein allergens or PRP-allergens). In addition, insect damage also makes it easier for fungi to invade, and then fungal toxin contamination will increase.

Natural pesticides, PRP-allergens and fungal toxins have a long history of harming people. When tested in the laboratory similarly to synthetic pesticides, natural pesticides cause the entire spectrum of disease that raise health concerns for human-made chemicals. Natural pesticides cannot be puny if they are to kill or deter insects and fungi. Clinical reports and studies in humans, domestic animals and laboratory animals show that, depending on exposure level, natural toxicants can cause cancer, birth defects, endocrine disruption, liver and kidney disease, and the like.

For example, search online with two words, “green potatoes” or “potato poisoning”, and you will find an abundance of information on potato glycoalkaloids (GA). Potatoes make more GA when attacked by pests, and post-harvest potatoes become green when exposed to light. In addition to greening, light causes an increase in GA, sometimes to dangerous levels. Cooking does not destroy these GA. Excess exposure to GA causes nausea, vomiting, diarrhea, abdominal pain and delirium. These symptoms are too common to make diagnosis easy. Historically, eating potatoes has caused deaths, but no deaths have been reported in many years. GA are but one class of potentially-toxic natural chemicals of foods, and it is only through knowledge that risk of poisoning is minimised. We have some knowledge of the short-term consequences of natural toxicants of foods, but very sparse knowledge about the long-term consequences. We do know there is no refuge in the thought that Mother Nature is always kind.

It is estimated that the quantity of natural pesticides in our foods is more than 10,000 times greater than the amounts of synthetic pesticide residues in our foods. Toxins contributed by fungal invasion add to this equation. A simple addition of risks from all the different natural toxicants in food will demonstrate that the vast majority of chemical risk to human health occurs from the natural toxicants. In spite of this vastly disproportionate risk from natural toxicants, nearly all of the focus of activists, media and government regulation is on synthetic pesticides. If we pay attention to Mother Nature our view of the world will change.

We can take advantage of Mother Nature if we want to eat less of the potentially harmful chemicals in our foods, both natural and synthetic. Farmers treat crops with pesticides to reduce damage from insects and fungi. When plants do not have to fight off insects and fungi, the plants make less of the natural pesticides and PRP-allergens. And, with good crop protection, plants will have less fungal toxin contamination. Compared to natural pesticides, it takes only a tiny amount of modern crop protection chemicals to protect crops from most attacks. The only way we can truly limit our exposure to all potentially harmful chemicals of foods, both natural and synthetic, is by regulating synthetic pesticides in a real-world context that includes Mother Nature.

We also ignore the dark side of Mother Nature in our quest for ‘naturally resistant’ crops. Plants that have elevated resistance to insect and fungal attack are resistant for a reason. It can be expected that increased natural resistance is due to higher levels of natural pesticides and possibly to increased levels of PRP-allergens. Thousands of published papers and several textbooks describe the toxic properties of these natural toxicants that contribute to pest resistance. Clearly, we should not be exposing large populations of people to increased levels of natural toxicants without a careful evaluation of changes in risk. Avoiding a tiny amount of vigorously tested and regulated synthetic pesticide by increasing the levels of largely untested, unregulated natural pesticides and PRP-allergens may not be a good trade.

NZFSA already takes a risk-based approach to food safety. NZFSA could readily lead the world in bringing the realities of Mother Nature into synthetic pesticide regulation through an alliance between plant scientists, toxicologists and risk assessors. This is how the real world works, and this is how pesticide regulation should work.

Dr Joel Mattsson is a retired toxicologist who worked for 25 years at The Dow Chemical Company and Dow AgroSciences LLC, Indiana, USA. During that time he conducted toxicology testing and safety research on synthetic and biotechnology plant-incorporated pesticides. He is a past President and Vice-President of the Food Safety Specialty Section, Society of Toxicology.

Each issue our columnist gets to air their personal views on a subject close to them. These views do not necessarily represent those of the New Zealand Food Safety Authority, but are published here to encourage debate on issues of current interest.