Limitations of epidemiology

May 2014

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 In the absence of any prior clinical testing, nor controlled release into the food chain with labelling and monitoring, the last resort for GM safety 'testing' is epidemiology. This means looking at entire populations (which in America means 300 million people) to see if an undefined and undefinable adverse reaction is emerging. Looking for an unknown object in a haystack has little chance of success.

Recent concerns have been raised regarding the potential for Roundup herbicide or its active ingredient, glyphosate, to cause cancer [1,2]. However, a review of US epidemiological studies of glyphosate and cancer carried out in 2011 and published in 2012 reported “no consistent pattern of positive associations indicating a causal relationship between total cancer (in adults or children) or any site-specific cancer and exposure to glyphosate.” (Mink)


This sounds convincingly definitive, until you place it in the context of the ocean of cancer-causing substances and cancer-friendly life-styles in which the studied population lives. Are epidemiologists looking for hay in haystack?

The authors themselves pointed out that it is impossible to determine the actual exposure to glyphosate of the individuals in the surveys they reviewed (the scale of this problem is explained in [3]).  

There are other obvious limitations.

The data were acquired using health records, personal accounts of pesticide usage where possible, and farmers licensed (and trained) to apply pesticides. The health records are largely pre- or early-GM crop use. This means the quantities of Roundup being sprayed, and potential exposure to it, were much lower than the situation today. Pesticide applicators are trained in how to protect themselves and may have less exposure to the chemicals they're spraying than bystanders. In other words, the studies may be based on a population with low exposure to Roundup/glyphosate. Personal accounts are always highly unreliable. 

Intriguingly, the review was carried out by a consulting firm, 'Exponent' (previously known as 'Failure Analysis Associates', holding company 'The Failure Group').  

This firm specialises in post-disaster analysis such as the “Collapse of the World Trade Center” and “Exxon Valdez”.

Why would Exponent be looking for a disastrous cancer-link between one of the oldest and most widely used weedkillers in the world? Especially when this possibility has already been dismissed by US and other regulators around the globe?

Put another way, who would pay for no less than four Exponent consultants to carry out a review on a concern which regulators by all accounts consider to be dead in the water?

The paper itself tells us who paid: “This research was supported by the Monsanto company, St Louis, Missouri”.

Note that the review pre-dates Séralini's rat feeding study which suggested a cancer link to both Roundup and GM maize. Did Monsanto already know something about Roundup it hasn't told us? The paper has all the hallmarks of a damage-limitation exercise, but it was launched before the damage emerged.

Tell our government we want properly controlled scientific testing of GM food safety, especially for links to cancer.





Pamela J. Mink, et al., 2012, Epidemiologic studies of glyphosate and cancer: A review, Regulatory Toxicology and Pharmacology 63

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