4.5 A critique of substantial equivalence
In the late 1990s, the principle of substantial equivalence came under sustained attack, and at this point it is worth examining both the points of criticism and the responses. In October 1999, Erik Millstone, Eric Brunner and Sue Mayer published a critical commentary on substantial equivalence in the journal Nature.
Before you read some extracts from this article it is worth commenting both on the nature of the article and who the authors are. The article is a 'commentary' published within a respected journal that also publishes formal peer-reviewed papers. The journal's editors argue that it is important to publish 'original and stimulating opinions', without implying any endorsement of the views expressed. Millstone is an academic with a science background who specialises in science policy. Brunner is also an academic, specialising in epidemiology and public health. Mayer is a scientist working for the pressure group Gene Watch. These people are not working biotechnologists, but they have all been active participants in the debates surrounding GM crops.
Box 1 contains five key extracts from the article, numbered for convenience. As you read the extracts, you should undertake the following activity.
Box 1: Extracts from 'Beyond Substantial Equivalence'
E. Millstone, E. Brunner and S. Mayer, Nature, October 1999.
The concept of substantial equivalence has never been properly defined; the degree of difference between a natural food and its GM alternative before its 'substance' ceases to be acceptably 'equivalent' is not defined anywhere, nor has an exact definition been agreed by legislators. It is exactly this vagueness that makes the concept useful to industry but unacceptable to the consumer.
The concept of substantial equivalence emerged in response to the challenge confronting regulatory authorities in the early 1990s […] One obvious solution at that time would have been for legislators to have treated GM foods in the same way as novel chemical compounds, such as pharmaceuticals, pesticides and food additives, and to have required companies to conduct a range of toxicological tests, the evidence from which could be used to set 'acceptable daily intakes' (ADIs).
The challenge of how to deal with the issue of risk from consuming GM foods was first confronted in 1990 at an international meeting, of the FAO and the WHO. The FAO/WHO panel report […] does not use the term 'substantial equivalence' or mention ADIs. It implies that GM foods are in some important respects novel, but it then argues that they are not really novel at all - just marginal extensions of traditional techniques. These inconsistencies are inevitable, given that the industry wanted to argue both that GM foods were sufficiently novel to require new legislation - and a major overhaul of the rules governing intellectual property rights - to allow them to be patented, yet not so novel that they could introduce new risks to public or environmental health.
Unfortunately, scientists are not yet able reliably to predict the biochemical or toxicological effects of a GM food from a knowledge of its chemical composition. For example, recent work on the genetics of commercial grape varieties shows that, despite detailed knowledge, going back for centuries, of the chemistry and flavour of grapes and wines, the relationship between the genetics of grapes and their flavour is not understood. Similarly, the relationship between genetics, chemical composition and toxicological risk remains unknown. Relying on the concept of substantial equivalence is therefore merely wishful thinking: it is tantamount to pretending to have adequate grounds on which to judge whether or not products are safe.
Substantial equivalence is a pseudoscientific concept because it is a commercial and political judgment masquerading as if it were scientific. It is, moreover, inherently antiscientific because it was created primarily to provide an excuse for not requiring biochemical or toxicological tests. It therefore serves to discourage and inhibit potentially informative scientific research. […] If policymakers are to provide consumers with adequate protection, and genuinely to reassure them, then the concept of substantial equivalence will need to be abandoned, rather than merely supplemented. It should be replaced with a practical approach that would actively investigate the safety and toxicity of GM foods rather than merely taking them for granted, and which could give due consideration to public-health principles as well as to industrial interests.
As you read the five extracts in Box 1, write brief comments on the authors' arguments (in the margins, if you wish). For each extract, you should try to assess the validity of the points being made. Do you agree or disagree? If so, explain your reasons.
The notes given here are far more detailed than I would expect you to make, so do not be concerned if you have not written this much. You should be aware that whilst I may differ with the authors over points of detail, I am broadly sympathetic with their arguments. You should keep that in mind when comparing your comments with my own.
I agree with the authors that substantial equivalence, as it was initially defined, was a vague concept. It is certainly true that the regulatory scientists did not initially offer precise ways in which equivalence could be measured. Many proponents of GM food, perhaps for good scientific reasons, believe that GM food is always substantially equivalent to its traditional counterpart. They believe that if the products of the novel genes can themselves be proved to be safe, then the GM product will be safe. This strong belief has meant that in the USA, at least, there appeared to be very little safety testing before the initial GM products were released on to the market, or grown commercially.
I think that the authors claim that animal feeding experiments could easily be used to generate ADIs is problematic. As we have already discussed, in order to generate data equivalent to those generated in pharmaceutical or related tests, one would have to feed unnaturally large amounts of the product to laboratory animals. Given that many GM crops are staples, animals would also have to be fed supplementary foodstuffs in order to maintain a balanced diet. I think it unlikely that such a procedure could produce reliable results. That is not to say that the most obvious alternative, of feeding animals a normal diet but with elevated levels of the relevant proteins, DNA or other compounds characteristic of the GM material, would be without problems. The difficulty in designing and interpreting such tests should be apparent from our discussion of the Pusztai case (Section 2).
I think the authors have hit on a fair point here. There is a contradiction at the heart of the drive to commercialise GM products. They must be novel enough that they can be patentable, but not so novel that they can be seen to be in any way substantially different from their conventional counterparts.
Given the complexity of composition of any plant, a simple description of the components present in a plant is unlikely to give a clear indication of anything other than the presence of obviously high levels of toxins. I think the authors are right to point out this difficulty (but see the response quoted later in Section 3).
I think that in many respects the authors are right to identify the principle as a barrier to further research, certainly as it had been interpreted up to that time. I believe that there was a tendency to assume substantial equivalence without the necessary scientific experiments to support the assumption. However, in the broadest sense, I think that substantial equivalence is a reasonable starting point in a scientific risk assessment. Given that GM products are being developed, it is difficult to see how one could assess their safety without some sort of comparison with traditional products. Even if the term 'substantial equivalence' was abandoned, an experimental safety testing procedure would have to include some sort of control, which I would tend to assume would be the traditional product.