The Increasingly Toxic Pesticide Treadmill


"Just pick up a single apple. It may bear a proud label of its country of origin, but if it’s been commercially grown, it will have been treated with at least 2 out of 23 possible herbicides, and 34 pesticides and fungicides currently available. In the case of pesticides, the tree could have suffered some 40 applications during a single growing season. There’s no label to tell you that."

- Lance Reynaud, Author and Chef.

It has always seemed logical to me that if you spray chemicals designed to kill insects and rodents onto food, these pesticides will also destroy the tiny microbe colonies in our soil, turn water toxic, damage animals and, in the end, make their way into people’s bodies and kill our own gut microbiome.

Consider that ‘icide’ comes from the Latin cīda (killer), cīdium (act of killing), derivatives of caedere (to cut down, kill), and in compounds cīdere (to strike). Besides pesticides, other examples include weedicide, fungicide, suicide and homicide!

Humans have been using pesticides to control (or attempt to control), kill and repel insects and other arthropods, plant pathogens, weeds, rot fungi and rodents for thousands of years. It has been only within the last 70 years that significant progress has been made. The basic argument for the use of these ‘icide’ chemicals is that spraying chemicals will kill weeds and specific insects and rodents, and thus increase yields and profits – and that small amounts of pesticides are safe to the human body.  

This is of course a fallacy and this is how we know...

A decline in the effectiveness of pesticides is currently taking place – and has been for quite some time now. Application rates (amounts used) that were initially effective at wiping out insect populations began to lose their effectiveness. Applications were increased to regain the initial levels of control, but the levels of control seemed to decline even more rapidly.

What was happening? Initially, an application of pesticide will reduce insect populations. Some get a lethal dose and are immediate casualties, but there are always others that survive.

How? Some dive for cover under a protective leaf, some are missed completely as the wind takes the spray over the plant and onto another field, others may get some of the chemical, but not enough to be fatal, and then there are those that develop a resistance to the pesticide through natural selection. This is broadly called pesticide or field resistance.

Pesticide resistance is largely a genetically based phenomenon. Those individual insects that survive frequently have done so because they are genetically predisposed to be resistant to the pesticide. The most resistant organisms will then pass on their genetic traits to their offspring, and with each generation the genetic resistance will continue. Eventually, the whole population will survive the exposure to the pesticide and will be resistant, and this can happen quickly.

Compared to a human with a nine-month gestation period, the reproduction of most insects can be rapid. A whole generation can take place in a matter of weeks – many generations can be produced in a single season or year. The more times a population is exposed to a pesticide, especially a broad-spectrum pesticide, the more quickly resistance will develop.

This evolution is going strong in conventional agriculture today. Scientists point out that conventional agriculture is in an evolutionary arms race against the bugs, and we’re losing – on many fronts.

Insects that were once major threats to human health and agriculture but that were brought under control by pesticides are on the rebound.

Many studies show that there are now over 500 species of insects and mites resistant to pesticides.[i] Other sources estimate the number to be around 1000 species since 1945. There are also currently 457 unique cases of weeds globally that are resistant to the pesticides that once controlled them.[ii]

Multiple resistances – resistance to more than one pesticide and to pesticides in more than one chemical class – are also increasing rapidly. There are over 1000 insect/insecticide resistance combinations, and at least 17 species of insects that are resistant to all major classes of insecticide.

This is how farmers get trapped on the pesticide treadmill and end up using more - and increasingly toxic - chemicals to control pest populations that continue to develop resistance to each new pesticide. 

Clever little buggers aren't they?! (The bugs I mean).

Despite this resistance, and against all logic, the use of pesticides continues to grow. In 1964 the world used 265 million kilograms (589 million pounds) of pesticides in agriculture. The worldwide use of pesticides increased to 500 million kilograms (1.1 billion pounds) in 1991. 

The current world usage of pesticides is 3.3 billion kilograms (7.27 billion pounds) a year.

With these statistics in mind, the other front we are losing on is human health. The impacts are significant and wide-ranging, affecting every part of the body, and can include acute poisoning, cardiovascular disease, skin and eye problems, liver and kidney damage, reduced fertility and fecundity, early onset puberty, endometriosis, multiple chemical sensitivity, cancers, and neurological, endocrine, developmental, respiratory and immunological disorders.[iii]

It has been calculated that 25 million people a year die from pesticide poisoning, and that children in homes that use pesticides have a seven times greater chance of contracting some form of leukaemia.[iv]

There is also a considerable body of evidence that links pesticides to a range of cancers (and in particular to childhood cancer) resulting from both parental and direct childhood exposures. The evidence is strongest for leukemia and brain cancer, but there is also an association with non-Hodgkin’s lymphoma, neuroblastoma (a tumour in nerve tissue), Ewing’s sarcoma (a tumour of bone tissue), Wilm’s tumour (kidney), germ cell cancer, Hodgkin’s disease, eye cancer, renal and liver tumours, thyroid cancer and melanoma. Maternal and paternal exposures pre-conception – including both occupational and household exposures – are also associated with leukemia and brain cancer. Swedish research has concluded that adult cancer risk is largely established during the first 20 years of life.[v]

Exploring the relationship between ADHD and exposure to organophosphate pesticides, researchers analysed the levels of pesticide residue in the urine of more than 1100 children aged 8 to 15 and found that those with the highest levels of dialkyl phosphates, which are the breakdown products of organophosphate pesticides, had the highest incidence of ADHD and behavioural disorders.

Overall, they found a 35 per cent increase in the odds of developing ADHD with every tenfold increase in urinary concentration of the pesticide residue. The effect was seen even at the low end of exposure: children who had any detectable, above-average level of the most common pesticide metabolite in their urine were twice as likely as those with undetectable levels to record symptoms of learning disorders.[vi]

A review of pesticide exposure studies concluded that all of the high-quality birth defect studies reported positive associations with hypospadias (a defect in baby boys where the opening of the urethra is on the underside or near the tip, rather than at the tip, of the penis), cryptorchidism (the absence of one or both testes) and micropenis, spina bifida and congenital heart disease.[vii]

For all these reasons – health, economic, environmental, intergenerational – it’s more important than ever before to support and consume fresh, organic, spray-free, local produce. An increase in consumers demanding organic food will lead to an increase in farmers farming this way! Increased demand = increased supply.

Farmer and ecologist Wendell Berry’s now famous formulation that "eating is an agricultural act" is perhaps the original prompt for rethinking how we do food in our everyday lives today. The time is now.

Written by Dr Sarah Lantz.

[i] Gut, L. Schilder, A. Isaacs, R. & McManus, P. Fruit Crop Ecology and Management, Chapter 2, Managing the Community of Pests and Beneficials, 2002. [cited 2016 January 18] Available at: www. how_pesticide_resistance_develops.

[ii] International Survey of Herbicide Resistant Weeds [cited 2018 June 5] Available at: http://

[iii] Maclennan, P. et al. (2002) Cancer incidence among triazine herbicide manufacturing workers, JOEM 44(11): 1048–1058; Sass, J. (2003) Letter to the editor, JOEM 45(4):1–2

[iv] Sears, M. & Genius, C. S.(2012) Environmental Determinants of Chronic Disease and Medical Approaches: Recognition, Avoidance, Supportive Therapy and Detoxification, J Environ Public Health 1–15; Sears, M. Walker, C. et al (2006) Pesticide assessment: protecting public health on the home turf, J Paediatr Child Health 11 (4):229–34; Sanborn, M. Kerr, K. Sanin, L. Cole, D. Bassil, K.
& Vakil, C. (2007) Non-cancer health effects of pesticides: systematic review and implications
for family doctors, Can Fam Physician, 53, (10):1712–20; Bassil, K. Vakil, C. Sanborn, M. Cole, D. Kaur, J. & Kerr, K. (2007) Cancer health effects of pesticides: systematic review, Can Fam Physician 53(10):1705–11.

[v] Van Maele-Fabry, G. Lantin, A. C. Hoet, P. & Lison, D. (2010) Childhood leukaemia and parental occupational exposure to pesticides: a systemic review and meta-analysis, Canc Cause Contr 21:787–809; Carozza, S.E. Li, B. Elgethun, K. &Whitworth, R. (2008) Risk of childhood cancers associated with residence in agriculturally intense areas in the United States, Environ Health Perspect 116(4):559–65; Thompson, J. Carozza, S. & Zhu, L. (2008) Geographic risk modeling of childhood cancer relative to county-level crops, hazardous air pollutants and population density characteristics in Texas, Environ Health 7:45; Lyons, G. & Watterson A. A Review of the Role Pesticides Play in some Cancers: Children, Farmers and Pesticide users at Risk? CHEMTrust, UK, 2010 [cited 2018 June 5] Available at: http://

[vi] Jurewicz, J. & Hanke, W. (2008) Prenatal and childhood exposure to pesticides and neurobehavioural development: review of epidemiological studies, Int J Occup Med Environ Health 21(2):121–32; Nielsen S. & Mueller B. (2010) Childhood brain tumors, residential insecticide exposure, and pesticide metabolism genes, Environ Health Perspect 118:144–49; London, L. Beseler, C. et al. (2012) Neurobehavioural and neurodevelopmental effects of pesticide exposures, Neuro Toxicol 33(4):887–96.

[vii] Nassar, N. Bower, C. & Barker, A. (2007) Increasing prevalence of hypospadias in Western Australia, 1980–2000, Arch Dis Child 92(7):580–84

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