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RMIT's Professor Marc Cohen

The ten toxic truths

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PROFESSOR MARC COHEN investigates the effects of chemicals used in food production on the health of our soils, environment and bodies.

Ten Toxic Truths

By Professor Marc Cohen


It is widely recognised that the greatest underlying cause of death among humans today is lifestyle-related chronic disease. The world is in the grip of an epidemic of obesity, diabetes, cardiovascular disease, cancer, dementia and more, fuelled by a high intake of sugar, fat, salt, alcohol and tobacco, and a lack of physical activity. In addition to this voluntary consumption, the entire human population is exposed to a toxic cocktail of industrial chemicals. The impact of industrial chemicals on human health was recently highlighted by the World Health Organisation, which forecasts a “tidal wave of cancer” (International Agency for Research On Cancer 2014).

Meanwhile, public health researchers suggest we are experiencing a “silent pandemic of neuro-developmental disorders” and a “chemical brain drain” brought about by the exposure of an entire generation to industrial chemicals (Grandjean 2014). There are many actions we can take to avoid voluntary and involuntary health risks and, rather than becoming despondent, we need to become more aware and vigilant.

Since the 16th century when Paracelsus stated “the dose makes the poison”, this idea has formed the basis for the regulation of toxic chemicals, including the use of pesticides and pharmaceuticals. We now know that this truth is incomplete. It is not only
the dose, but also the type of chemical, the timing of exposure, the combination of chemicals and individual risk factors that combine to produce toxic effects (see ‘Toxicity Depends On’ on page 49). These factors give rise to what I call the “10 toxic truths”.


Everyone is affected

Since the advent of the Industrial Revolution, industrial chemicals have permeated the globe and it is clear that the world will never return to the conditions that existed prior to this period. Many toxic chemicals are carried throughout the world dispersed as atmospheric aerosols, while billions of tons of chemicals and plastics have entered the oceans, resulting in plastic microparticles being reported in nearly every litre of ocean water. Toxic chemicals have now entered every habitat and ecosystem on earth, from the most arid deserts to the deepest seas, and virtually all living creatures now contain pollutants at or near harmful levels.

Toxic chemical exposure has become an inevitable part of modern life and everyone is affected. Toxic chemicals are pervasive in our food, soil, air, water and indoor environments as well as in all human tissue, including umbilical cord blood and breast milk.
Only a few countries such as the US, Canada and Germany have programs that aim to monitor toxic chemicals in their general population. The National Health and Nutrition Examination Survey (NHANES) conducted by the US Centers for Disease Control and Prevention includes the world’s most comprehensive assessment of human chemical exposures. The most recent NHANES report examined only 212 chemicals and found chemicals such as polybrominated diphenyl ethers (PBDEs), used as fire retardants, and bisphenol A (BPA), a component of epoxy resins and polycarbonates, in the vast majority of participants (Centers for Disease Control and Prevention 2009).


The full extent is unknown

While we are all chronically exposed to a toxic cocktail of industrial pollutants, the full impact of industrial chemicals on human health remains unknown. There are more than 80,000 industrial chemicals that are commercially produced with more than 3000 produced in high volume and many tens of thousands more being inadvertently produced from industrial processes. Yet while the number of industrial chemicals increases every year, in most cases it is not possible to determine a chemical’s ‘safe level’, or ‘toxicity threshold’. And even when levels are measured, it is often difficult to interpret their clinical significance.
The measurement of the body’s toxic load is still an emerging science (Sexton 2004, Committee on Human Biomonitoring for Environmental Toxicants, 2006). There are very few laboratories that currently have the facilities to perform comprehensive
measures of toxic chemicals and, as yet, there are no general assessment measures that doctors can request to assess the ‘toxic load’ or ‘body burden’ of their patients. Thus, even though the signs and symptoms of overdose or overt toxicity are known for some compounds, the relationship between toxic load, individual susceptibility, clinical symptoms and chronic disease is incredibly complex and far from understood.


Tiny doses can have big effects

In the past it was thought that dose-response curves were linear, displaying a direct relationship between dose and toxicity. It is now known that dose-response curves can be non-linear or ‘non-monotonic’. This occurs when chemicals disturb the body’s regulatory processes rather than just impacting on target organs or tissues. By disrupting the endocrine system, the potential to reap metabolic havoc is greatly increased and extremely small exposures – orders of magnitude below recognised safety levels – can have dramatic effects. The hazards of endocrinedisrupting chemicals and their potential for irreversible, latent effects was first brought into the public spotlight by Theo Colborn and Pete Myers in the mid-1990s with their book Our Stolen Future. In it they highlighted the science that shows that many chemicals, which are still being used, can impair reproduction, behaviour, intellectual capacity and the ability to resist disease in current and future generations.

The book also suggested that: “World-wide exposure to endocrine disruption has thrust everyone into a large-scale, unplanned, unintended experiment with health, the outcome of which may not be known for generations.” While at the time of its release Our Stolen Future was seen by many as alarmist, a 2013 joint report from the World Health Organisation and United Nations Environment Program on the ‘State-of-the-Science of Endocrine Disruptors’ confirms many of the book’s findings and suggests that exposure to industrial chemicals with endocrine-disrupting actions are contributing to the global increase in obesity, cancer, psychiatric diseases, birth deformities, ADHD and neuro-developmental problems in children, with current findings being “the tip of the iceberg”.


Biomagnification occurs up the food chain

Many toxic chemicals are fat soluble and last for decades in the environment where they undergo biomagnification (tissue concentrations increase) as they pass up the food chain. The toxicity of DDT and other persistent organic pollutants (POPs) (see ‘The rise of pesticides’ box on page 47) was first brought to the public’s attention in 1962 by Rachel Carson in her book Silent Spring. In May 2004, the Stockholm Convention on POPs came into effect, banning the use of nine of the most dangerous pesticides along with dioxins, furan and polychlorinated biphenyls (PCBs). These so-called legacy chemicals were all known to persist in the environment; undergo long-range environmental transport; be toxic to humans; and biomagnify up the food chain.

Even though the use of most POP pesticides is banned in agriculture, these chemicals now permeate the global environment and lodge in the fatty tissue of animals where they biomagnify millions of times as they travel up the food chain. Being a precious biological resource, fat is seldom excreted, except for special situations such as breastfeeding where valuable fat (along with fat-soluble pollutants) is transferred to infants who sit at the very top of the food chain. POPs are also absorbed by micro-plastics in the oceans and are found in high concentrations in marine mammals, with some beached whales being classified as toxic waste.


Chemical cocktails are synergistic 

While exposure to individual toxic chemicals can be harmful, exposure to chemical mixtures is even more harmful. It has been shown that chemical cocktails can produce ‘something from nothing’ with toxic mixture effects arising even when the level of each contaminant in the mixture is below its specific ‘NOAEL’ (no observable adverse effect limit). Such mixture effects are not accounted for when determining chemical safety, which is assessed one chemical at a time, if at all. A 2009 ‘State of the Art Report on Mixture Toxicity’ commissioned by the European Union found that “there is consensus in the field of mixture toxicology that the customary chemical-by-chemical approach to risk assessment might be too simplistic. It is in danger of underestimating the risk of chemicals to human health and to the environment.”

While mixture toxicity is currently not accounted for in chemical risk assessments, it is actively used in pesticide formulations to increase their potency. In order to kill pests, pesticides contain active ingredients with their own inherent toxicity, yet when pesticides are packaged and used, they are prepared as formulations. Pesticide formulations include the addition of often unnamed and unlabelled adjuvants that are designed to make the active ingredient more potent by acting as surfactants and cell penetrants.

While these so-called ‘inert’ adjuvant chemicals are excluded from safety testing, recent research suggests they are far from inert and that they make formulations hundreds of times more toxic than the active ingredient alone (Mesnage 2014).


Bioaccumulation occurs over the lifespan

Over a human’s lifespan, exposure rates to fat-soluble chemicals often exceed the excretion rate leading to their accumulation in fatty tissue. Exposure begins in the womb with fat-soluble chemicals in umbilical cord blood crossing the placenta and lodging in foetal fat, which is mainly in the developing brain. A Canadian report has begun to document the extent to which children are born “pre-polluted” (Group 2005, WWF 2005, Canada 2013).

Throughout a person’s lifespan, combinations of persistent chemicals accumulate in fatty tissue such as the brain, breast, prostate and bone marrow, which are often the tissues that develop cancers in later years. In addition to persistent fatsoluble chemicals, there are many other water-soluble endocrinedisrupting chemicals such as BPA and organophosphate (OP) pesticides that
are ingested continually throughout a person’s lifespan, making them pseudo-persistent.


Windows of development are critical

The toxic effects of chemical exposure during critical periods, such as early childhood, can be irreversible. This became tragically evident in the 1970s with the birth of thousands of children without limbs and other birth defects after being exposed in utero to thalidomide. More recently, in-utero exposure to OP pesticides has been shown to impair children’s intellectual development in later life (see Ref 1).


Effects are trans-generational

Parental exposure to industrial chemicals can affect offspring and future generations. Many chemicals interfere with biochemical and
endocrine pathways; induce genetic and developmental abnormalities; and produce trans-generational epigenetic effects that may lead to abnormalities in the third or fourth generation post-exposure. This can influence all aspects of an individual’s life history.
This has recently been demonstrated experimentally with a single exposure to a commonly used fungicide being shown to alter the
physiology, behaviour, metabolic activity and brain development in offspring three generations later, changing how they perceive and respond to a stress (see Ref 2).


Risk is unequal, unjust and greater for the young

The health risks of chemical exposures differ according to individual risk factors that include health status, physiology and genetics as well as demographic and social differences. Children are most vulnerable due to their higher dietary exposure, contact with the ground, hand-to-mouth behaviour, higher metabolic activity, immature organ systems, longer latency period for developing disease and sensitive development windows so that exposures lead to lifelong consequences (Landrigan 2005).

The US-based Pesticide Action Network recently published a review of the scientific literature titled ‘Generation in Jeopardy: How
pesticides are undermining our children’s health and intelligence’, which reports on the many studies that demonstrate that pesticide
exposure compromises children’s cognitive function and leads to later chronic disease (Schafer 2013).


Exposure is unequal and unjust and accidents happen

Everyone is exposed to industrial pollutants, yet exposure risk is not equal. Exposures vary with age, income, education, ccupation,
location, lifestyle, public policy and proximity to industrial activity and accidents. People living in poverty and lower socio-economic conditions often have the greatest exposure, which then compounds the effects of wealth inequality (Wright 2009). This makes environmental justice an important issue.

Industrial accidents raise further justice issues as catastrophic accidents have inadvertently exposed vast populations of humans and wildlife to industrial pollutants. These accidents have occurred at every stage of the chemical-production cycle including mining (BP oil spill); transport (Exxon Valdez); manufacture (Bhopal); use (Fukushima and Chernobyl); and disposal (Love Canal). What’s more, often accidents are associated with minimal, delayed and inadequate compensation and remediation measures.

Here are the detailed references for this article including ‘Ref 1’ and ‘Ref 2’ for Toxic Truths 7 & 8 respectively.


Ref 1: Bouchard, M., Chevrier, J., Harley, KG., Kogut, K., Vedar, M., Calderon, N., Trujillo, C., Johnson, C., Bradman, A., Barr, DB., Eskenazi, B. (2011). “Prenatal exposure to organophosphate pesticides and IQ in 7-year-old children.” Environ Health Perspect 119(8).

Ref 2: Crews D, G. R., Scarpino SV, Manikkam M, Savenkova MI, Skinner MK. (2012). “Epigenetic transgenerational inheritance of altered stress responses.” Proc Natl Acad Sci 109(23): 9143-9148 

Baillie-Hamilton (2002). “Chemical toxins: a hypothesis to explain the global obesity epidemic.” J Altern Complement Med. 2002 Apr;8(2):185-92.

Bouchard, M., Chevrier, J., Harley, KG., Kogut, K., Vedar, M., Calderon, N., Trujillo, C., Johnson, C., Bradman, A., Barr, DB., Eskenazi, B. (2011). “Prenatal exposure to organophosphate pesticides and IQ in 7-year-old children.” Environ Health Perspect 119(8).

Canada, E. D. (2013). Pre-polluted: A report on toxic substances in the umbilical cord blood of Canadian newborns. Toronto.

Carson, R. (1962). Silent Spring. New York, Houghton Mifflin.

Centers for Disease Control and Prevention (2009). Fourth National Report on Human Exposure to Environmental Chemicals, US Department of Health and Human Services Committee on Human Biomonitoring for Environmental Toxicants. (2006). Human Biomonitoring for Environmental Chemicals  National Research Council

Crews D, G. R., Scarpino SV, Manikkam M, Savenkova MI, Skinner MK. (2012). “Epigenetic transgenerational inheritance of altered stress responses.” Proc Natl Acad Sci 109(23): 9143-9148

Curl, C., Fenske, FA., Elgethun, K. (2003). “Organophosphorus Pesticide Exposure of Urban and Suburban Preschool Children with Organic and Conventional Diets.” Environmental Health Perspectives 111(3): 377-382.

Grandjean, P., Landrigan, P.J. (2014). “Neurobehavioural effects of developmental toxicity.” The Lancet 13(3): 330-338.

Group, E. W. (2005). Body Burden: The Pollution in Newborns. Washington, DC.

International Agency for Research On Cancer (2014). World Cancer Report 2014. B. W. Stewart, Wild, C.P.,. Geneva, World Health Organisation.

Krüger, M., Schledorn, P., Schrödl, W., Hoppe, H.W., Lutz, W., Shehata, A.A., (2014). “Detection of Glyphosate Residues in Animals and Humans.” Journal of Environmental & Analytical Toxicology 4(2).

Landrigan, P., Garg, A. (2005). Children are not little adults. Children’s health and the environment: A global perspective – A resource manual for the health sector. J. Pronzczuk de Garbino. Geneva, World Health Organization.

Lu, C. and K. Toepel, Irish, R., Fenske, RA., Barr, DB., Bravo, R. (2006). “Organic diets significantly lower children’s dietary exposure to organophosphorus pesticides.” Environ Health Perspect 114: 260–263.

Mesnage, R., Defarge, N., Spiroux de Vendômois, J., & Séralini, G.-E. (2014). “Major pesticides are more toxic to human cells than their declared active principles.  .” BioMed Research International: 1-15.

Oates, L., Cohen, M., Braun, L., Schembri, A., Taskova, R., (2014). “Reduction in Urinary Organophosphate Pesticide Metabolites in Adults after a Week-Long Organic Diet.” Environmental Research 132: 105-111

Schafer, K., Marquez, EC. et al. (2013). Generation in Jeopardy: How pesticides are undermining our children’s health and intelligence. Oakland CA, Pesticide Action Network.

Sexton, K., Needham, LL., Pirkle, JL. (2004). “Human Biomonitoring of Environmental Chemicals.” American Scientist 92: 38-45.

van der Sluijs, J. P., Simon-Delso, N., Goulson, D., Maxim, L., Bonmatin, J.M., Belzunces, L.P. (2013). “Neonicotinoids, bee disorders and the sustainability of pollinator services.” Current Opinion in Environmental Sustainability 5(3-4): 293–305.

Vogt, R., D. Bennett, D. Cassady, J. Frost, B. Ritz and I. Hertz-Picciotto (2012). “Cancer and non-cancer health effects from food contaminant exposures for children and adults in California: a risk assessment.” Environmental Health 11(1): 83.

WHO/UNEP (2013). State of the science of endocrine disrupting chemicals – 2012: An assessment of the state of the science of endocrine disruptors prepared by a group of experts for the United Nations Environment Programme (UNEP) and WHO. Geneva, World health Organisation & United Nations Environment Program.

Wright, R. J. (2009). “Moving towards making social toxins mainstream in children’s environmental health.” Curr Opin Pediatr 21(2): 222-229.

WWF, G. (2005). A present for life: hazardous chemicals in umbilical cord blood. Amsterdam.

Zeng, G., Chen, M., Zeng, Z. (2013). “Risks of Neonicotinoid Pesticides.” Science 340: 1403.


The 10 Toxic Truths – In short form

1) Everyone is affected

Toxic chemicals are pervasive and are distributed through long-range environmental transport so that all living things contain pollutants at or near harmful levels. Toxic chemicals are found in all human tissues and in food, soil, air, water and indoor environments.

2) The full extent is unknown 

Toxic chemicals are often invisible and have latent effects. Over 80,000 chemicals are produced commercially and industrial processes inadvertently create many more. Most chemicals are not tested for toxicit – and very few are routinely tested for in human tissue. 

3) Tiny doses can have big effects

Dose responses can be non-linear with extremely small doses of endocrine disrupting chemicals (EDCs) contributing to the global increase in obesity, birth deformities, cancers, psychiatric diseases and neurodevelopmental problems with current findings being “the tip of the iceberg”.

4) Bio-magnification occurs up the food chain

Persistent organic pollutants (POPs) last for decades in the environment, accumulate in fatty tissue and magnify up the food-chain. Bio-magnification leads to much higher concentrations in predatory species and human infants who sit at the top of the food-chain.

5) Windows of development are critical

The toxic effects of exposure during critical periods can be irreversible, yet remain hidden until later in life. Early exposure can impair intellectual development and metabolism and foster the development of metabolic syndrome, cancer and other chronic diseases.

6) Effects are trans-generational

Parental exposure to industrial chemicals affects offspring and future generations. Industrial chemicals can induce genetic and developmental abnormalities and transgenerational epigenetic effects that can lead to abnormalities in the third and fourth generation post-exposure.

7) Chemical cocktails are synergistic

Exposure to chemical mixtures is more harmful than individual chemicals. Mixture effects can produce ‘something from nothing’, with toxicity arising even when individual chemical concentrations have no effect, yet chemicals are tested for safety individually, if at all.

8) Bioaccumulation occurs over the lifespan

Exposure rates of fat-soluble chemicals often exceed the excretion rate leading to accumulation over the lifespan in fatty tissue such as the brain, breast, prostate and bone marrow. This accumulated body burden crosses the placenta and targets the fetal brain.

9) Risk is unequal, unjust and greater for the young

Risks vary with physiology, genetics, demographics and income. Children are most vulnerable due to higher dietary exposure, contact with the ground, hand-to-mouth behavior, higher metabolic activity, immature organ systems and a longer latency period for developing disease.

10) Exposure is unequal and unjust and accidents happen

Exposure is not equal and varies with age, income, education, occupation, location, lifestyle, public policy and proximity to industrial accidents. Accidents that inadvertently expose vast populations to toxic chemicals happen at every stage of the industrial chemical lifecycle.

Professor Cohen’s Ten Toxic Truths article appeared in the March/April 2015 issue of Organic Gardener magazine.