industry & research
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Agriculturalists also take issue with
WHO’s decision, arguing that glyphosate
has helped produce significantly higher
yields since the 1980s and improved
soil by doing away with till farming.
According to the chairman of Grain
Producers Australia, Andrew Weidemann:
“A ban on glyphosate would be a disaster
agronomically.”
Ivan Kennedy, professor emeritus in
agricultural and environmental chemistry
at the University of Sydney, spoke
with Campus Review about WHO’s
classification of glyphosate, the recent US
verdicts and what Australian agriculture
would be like without glyphosate.
CR: Professor, you believe WHO’s labelling
of glyphosate as a probable carcinogen to
humans was a bad decision. Why?
IK: I’ve been reassuring farmers for some
years now that they have nothing to fear
from glyphosate. I do that on the basis
of lots of evidence, essentially [evidence]
that has been used for the last 40 years.
I also do it based on glyphosate’s actual
structure and its mode of action. It consists
of three parts: one that you could think of
as carbon dioxide; another is ammonia;
and the third is phosphate. These are all
essential elements in our nutrition and
metabolise in our body.
The likelihood that such a compound
would be carcinogenic is inherently
unlikely. Glyphosate has none of the
features of common carcinogens. It’s
not aromatic, it doesn’t have halogens,
it doesn’t contain heavy metal. Just on
that basis, I find any suggestion that it is
carcinogenic most unlikely.
Nevertheless, around the world, the
various agencies – the European Food
Safety Agency, the Food and Agriculture
Organization, the United Nations, the
Pest Management Regulatory Agency of
Health Canada, the US Environmental
Protection Agency, as well as the
Australian Pesticides and Veterinary
Medicines Authority – attest to the lack of
carcinogenicity in many trials that have
been conducted.
You have to remember that Roundup
itself has adjuvants, other chemicals,
which vary from time to time, depending
upon the projected use. Possibly some
of those, generally speaking, are more
toxic, and perhaps some of those might
have some influence. I’m not an expert on
carcinogenicity myself.
Many agriculturists believe that glyphosate
is a wonder chemical, because it can
precisely target weeds. Why are we
unlikely to create a similar chemical?
Well, in a sense, it was found by accident.
I’m sure the researchers that found it were
seeking something as good, but its mode
of action is to interfere with an enzyme
occurring only in plants.
It’s a shikimate synthase, which makes
shikimic acid, which is an essential
precursor for making lignin and wood.
Of course, plants are the only species
– perhaps as well as a small number of
bacteria – that can actually carry out
these reactions.
You can’t really design for something
like that unless you’ve got that kind of
intimate knowledge that glyphosate
mimics phosphene or pyruvate, which
is a key element in our metabolism.
So it looks like phosphene or pyruvate,
but only to this particular enzyme that
occurs in plants. None of the enzymes in
animals that use phosphene or pyruvate
are affected.
The Grains Research and Development
Corporation, as well as Bayer in Europe,
have had a program in recent years –
a well-funded program – to engage
expert chemists on planning to develop
replacement chemicals. I’m not fully
up-to-date on that program, but I haven’t
heard if it’s come up with anything that
has the particular characteristics of
glyphosate.
Glyphosate acts directly on plants,
through the leaves. As soon as it hits the
soil, it becomes inactivated, so it has very
little residual effect, unlike most other
herbicides, some of which can hang
around for months affecting other plants
and also exerting any possible toxicity that
they have.
I’m going to turn to the legal matters
here, and I know this is not necessarily
your area, but I’m sure you would have
an opinion on it. Do you think the fact
that a jury and not a judge decided on
the Monsanto verdicts influenced the
outcomes of the US lawsuits?
I certainly do. Obviously in cases involving
cancer, there’s an emotional element. A
jury, of course, is not equipped to handle
the scientific evidence. It’s not decision-
making that they’re accustomed to using.
Very few of them are likely to be experts
in the area, so I think the court cases in
the US have been civil cases where the
standard of evidence is much lower than
other parts of the justice system.
Personally, I would prefer to see such
court cases conducted by judges who
would consult with experts arguing
on both sides, and really weigh up the
evidence on that basis. That’s certainly
my opinion. I don’t really think juries are
equipped to make these sorts of decisions
on a scientific basis.
Critics of glyphosate, and Bayer more
generally, say that denying that glyphosate
is a carcinogen is akin to what happened
with Big Tobacco. They argue that vested
interest groups paid for certain kinds of
research outcomes and so on. Is this a fair
call, or is the science still undecided?
I don’t think it’s a fair call. In the case of
tobacco, and the mechanism of cancer,
that was pretty obvious. The compounds
that are in tobacco smoke can be
demonstrated to be carcinogenic. Just
in the way that the carbon products that
you get from your barbecue steak can be
carcinogenic, but only at a very low rate.
In the case of tobacco, it’s clear that the
scientific evidence was that it was cancer
causing. In the case of glyphosate, there’s
The likelihood
that such a compound
would be carcinogenic is
inherently unlikely.
no such evidence for that carcinogenicity.
Certainly in humans. There is some
work that’s been done with animal
species that are very prone to developing
cancer. There’s a suggestion, and I think
that’s what the International Agency for
Research on Cancer was thinking of when
they made their decision.
In my opinion, they should have
restricted the judgment to possible
cancer, and I think their object is really
to encourage research. They make a
qualitative judgment, just based on the
public literature. They don’t do anything
quantitative; they don’t do a proper risk
assessment. Really, they’re just ringing a
bell: “Here’s something to look at.”
But that should never have become
evidence in a legal situation. ■
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