Public Opinion, Precaution and Toxicology

There is news today that a coroner in New Zealand formally ruled that the excessive consumption of Coca Cola led to the untimely death of Natasha Harris three years ago. Harris, it seems, developed a nasty habit of drinking up to 10 litres a day. “I find that when all the available evidence is considered, were it not for the consumption of very large quantities of Coke by Natasha Harris, it is unlikely that she would have died when she died and how she died” is what the coroner determined.

So what does this have to do with a blog about Canadian, politics and public opinion? Because this tragic incident illustrates a bedrock principle of toxicology that citizens, journalists and politicians often forget when our attention turns to issues of concern with possibly toxic substances. That principle is “the dose makes the poison.” It was formulated in the 16th century by the Swiss-German chemist Paracelsus and it holds that all substances (Coca-Cola included) are toxic in some quantity. Even something as seemingly innocuous as water can be toxic when enough has been consumed. This poor soul died from the excessive consumption of water during a brutal hazing ritual in New York. From this observation, the traditional role of toxicology has developed which is to ascertain at what level of exposure any given substance causes adverse effects.

With the rise of concerns about toxic substances in the post-World War II era, scientists have discovered some substances that deviate from this principle (see tamoxifen, an important drug in chemotherapy). But these effects are rare, difficult to demonstrate and the scientific debates that surround them are heated and complex. But when issues shift into the public and media spheres, the complex science behind these assertions, sadly, usually gets lost in the shuffle.
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There are multiple reasons for why this is. One reason is our own inability to perceive risks rationally. There is so much literature on the psychology of human risk perception that it is difficult to know where to start, but I might recommend this thispaper or this book. The long and short of the field of risk perception is that humans get very frightful about lots of things that actually present very little danger. After September 11th, Americans turned away from planes for their long trips and hopped into their cars, leading to a sharp increase in traffic fatalities in the months following.

Chemicals are one of those things that people fear a great deal. Ask people if they think the colourless, odourless chemical dihydrogen monoxide (the ingestion of which is the cause of thousands of deaths each year) should be banned and you’d be surprised (and a little concerned) at the number of people who would agree.

So when the public and the mass media turn their attention to issues of possible harm from exposure to chemicals, fears can be stoked, perspective can be lost and can lead, ultimately, to over- and unnecessary regulation of products and activity. For example, I was able to show in this paper that within-state newspaper coverage of Bisphenol A was positively linked to the chance that a US state legislature would introduce or adopt legislation banning products made with BPA the following year. It showed (again) the important role that increased media salience can have on policy changes. This, even though, scientific information suggests that exposure to BPA is hundres, if not thousands of times lower than the level at which there is a consensus that it causes adverse effects in rats (see here).

This research area is rife for investigation and it’s become a long-term project I’m working on, so I’m going to have a lot more to say about this in the future. I thought the news about Ms. Harris’ tragic death due to the excessive consumption of Coca-Cola was a useful way to set the stage for more thoughts and research to come.