How much evidence is enough evidence?

We hear all the time that the industrialized food that we eat and the objects made of plastic and alike that we use (may) contain toxic substances. In many cases, substances that cause cancer in humans: the so-called carcinogens. These substances are so omnipresent that most of us learned to ignore their existence. “I shouldn’t drink this soda because it may cause cancer, but oh well; if I keep thinking like this I won’t eat anything… so let’s just hope for the best!” But how much are we actually risking ourselves? How threatening is our “manmade” environment? And what seems to be the most urgent question: how can we possibly acquire these answers? The latest I read on the subject is this article from The New Yorker.
Let’s get the known case of cyclamates – a class of artificial sweetener. In the 1960’s there were several studies suggesting that cyclamates were carcinogens. In 1969 these substances were banned. Nonetheless, in the following years, new studies reported little evidence of its risk for humans. In the light of examples like this, the pressing concern is: what should we do in terms of food policies in face of the present evidence of risks for our health? When it comes to public policy, how much evidence is enough evidence?
When in the field of epistemology, it is ok to be very rigid about how much evidence is necessary in order to grant some finding the status of knowledge. The problem is that when in the field of public policy, matters are not theoretic, but urgently practical – and with potentially catastrophic consequences. Therefore, in the face of scientific evidence that some substance present in our food is carcinogen, the choice to either wait for more (robust) evidence or immediately act forbidding the use of the substance is crucial – just imagine the consequences of allowing hundreds of persons to die from an avoidable disease.
As highlighted in the article, “there is an inherent uncertainty in determining which substances are safe and which are not, and when their risks outweigh their benefits”. Nevertheless, we have to make decisions. Thus, we need this “epistemology for action”. I don’t know where to draw the line… anyone?

Related Article
Evidence in Medicine and Evidence-Based Medicine
By John Worrall , London School of Economics
(Vol. 2, November 2007)
Philosophy Compass

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