In this post we'll see why we no longer have to take any notice of claims that GMO crops and herbicides are not causing us harm. But first, let me put this in the context of this blog's major goal: to explain the importance of Swanson et al. and to defend it against its critics (for reference see below).
Yes, it’s high time to
up-armor for the coming fight. Ripples are already
spreading across the blogosphere, but so far the only
counterargument I’ve seen that went beyond the hoary old
“bad journal”, “bad credentials” Monsantoite b.s. was that the authors should
have separated different areas of America for statistical purposes. That’s because, if they were right, surely there should be
more chronic diseases where there was heavy spraying and less where there was
little or none.
GMO advocates never
tire of repeating the mantra “The poison is the dose”—even things you eat
unthinkingly every day, like table salt, can poison or even kill you if you eat
too much. Just the other day, a comment
by Chris Preston on a post on the Biofortified page (http://www.biofortified.org/2015/01/medical-doctors-weigh-in-on-glyphosate-claims/#comment-1340450) claimed “Toxicity
always depends on the dose. Regulators address whether a product can be used in
such a way that the dose received is below a level which may result in toxicity.” In technical terms, all substances with toxic
potential are monotonic—their toxicity may be zero at very low doses, but
increases proportionately with the size of dose.
This looks like a
general law, not just one for toxic substances. Surely the more you consume of
anything, the greater the effect? The
more food you eat, the fatter you get.
The more alcohol you drink, the drunker you get. Your common sense and your senses tell you
that. They also tell you that the sun
goes round the earth (not vice versa), that continents can’t creep around the
globe (they’re solid, lifeless rock, goddammit!), that we couldn’t possibly be
kissing cousins to chimps. But if our
senses and our common sense told us how things REALLY worked, there wouldn’t be
much need for science, would there? What
science does is prove that the counterintuitive thing is all too often the truth,
and I haven’t even mentioned quantum mechanics.
While we’re talking
about science, let me emphasize one of the most important things about it. It moves on.
It’s always moving on. It’s not
like religion, where you must believe exactly what people believed hundreds or
even thousands of years ago, or else be branded as a heretic. If you truly believe in science, you must always be
ready to change, because science is always changing, and once it’s changed,
what was science yesterday isn’t science any more. “The poison is the dose” is a case in point.
The assumption
behind “The poison is the dose” is that damage from any toxic substances can be
avoided if you simply make sure that people don’t get too much of it. And the mechanics of that seem
straightforward enough. There’s a nice
summary at http://www.animalresearch.info/en/drug-development/safety-testing/): “New medicines or chemicals which may affect
the health of humans are required by law to be tested on animals…Safety tests
begin with acute toxicity testing, where the animals are given a single dose of
the test compound. The aim of the tests is to determine the range between the
dose that causes no adverse effect and the dose that is life-threatening.”
Alas for that. According to Vandenberg et al. (“Bisphenol-A and the Great Divide: A Review of Controversies in the Field of Endocrine Disruption” Endocrine Reviews 30.1. 75–95, 2009), “a safe dose determined from high doses does not guarantee safety at lower, untested doses that may be closer to current human exposures.”
Alas for that. According to Vandenberg et al. (“Bisphenol-A and the Great Divide: A Review of Controversies in the Field of Endocrine Disruption” Endocrine Reviews 30.1. 75–95, 2009), “a safe dose determined from high doses does not guarantee safety at lower, untested doses that may be closer to current human exposures.”
Why not? It’s because for any toxic substance you can
plot a response curve, with a strong effect at or near the top of the curve and
a weak or null effect at the bottom.
And there is not just one possible curve--here's a sample of several:
Note that in all the figures, low-dose is to the left of the graph, high-dose to the right. The left-hand A and B graphs are the kinds of curve once thought to be universal (and still are by pro-GMOers). The right-hand C curve—the U-shaped curve—is very different, and probably the hardest one for GMO supporters to deal with.
That’s because of
the mode of testing described above—start high, work down until effects aren’t
apparent, leave what you think is a wide enough margin and announce a safe
dose. In other words, you plot only the
right-hand side of the U-curve. There’s
no way you could find that, at still lower levels, harmful effects could begin
again (left-hand side of the graph). But that's exactly what the graph means. It means that if a toxic substance has a U-curve but you like a good Monsantoite assume it's monotonic, it may very well have serious consequences that you literally cannot know about till after they've happened.
By now I’m sure GMO defenders will be saying. “Well, what’s the so-called scientific evidence
for all this? Some rubbish published in
a pay-for-play journal with a 0.something impact factor, I’ll bet.” Well, sorry, guys. “Endocrine Reviews has the highest Impact
Factor ranking of the 89 journals in the ISI category of endocrinology and
metabolism. Of the total 5,684 surveyed by ISI, EDRV's Impact Factor ranking is
#20.” (source: ResearchGate, but you can
also consult the original ISI lists.) The journal’s impact factor is 19.36, and
the paper itself has been cited in 537 other journal articles and books. We’re not talking junk science now; we’re talking
Gold Standard in Endocrinology.
Move on another three
years, and the same journal publishes “Hormones and Endocrine-Disrupting Chemicals: Low-Dose Effects and
Nonmonotonic Dose Responses” (Vandenberg et al., Endocrine Reviews 33.3. 378-455 (2012)). This is right in our ball-park because it
specifically includes glyphosate in its list of non-monotonic dose-response curve
substances that cause substantive harm:
Chemicals by
chemical class Nonmonotonic
effect Cell type
Glyphosate-based herbicide Cell death, aromatase activity HepG2 liver
(Round-Up) ERβ activity cells
Note that this paper has 564 citations, even better
than the previous one, especially since they cover only a two-year period. It includes nearly 850 citations of
supporting work.
Fallback position for GMOers: “This
stuff’s very controversial, you’re cherry-picking data, good science says the
opposite”. Well, six years ago (quite a
while in science at nowadays speeds) Laura Vandenberg wrote: “Although scientific inquiry is a dynamic
give-and-take among researchers with different opinions and viewpoints, the
so-called controversies surrounding low-dose effects and NMDR curves should be
put to rest, given that they now affect
public health decisions [My italics, DB]. These phenomena have been demonstrated time
and again for a sufficient number of endocrine-related endpoints, and they no
longer merit being considered ‘controversial’ topics.” In other words, this is the new orthodoxy in
toxicology.
So what has all this got
to do with Swanson et al.? Well, first
and foremost, it gets them off the “why no data by area” hook. If glyphosate has a low-dose effect, then
there is no reason to expect people in high-spraying areas to have more chronic
diseases, and therefore no point in separating data from different states or
regions.
But the work on response curves
goes much further than that. As
Vandenberg et al. point out at the end of their 2012 paper, “The concept of nonmonotonicity
is an essential one for the field of environmental health science because when
NMDRCs occur, the effects of low doses cannot be predicted by the effects
observed at high doses.” This means that when GMO advocates tell us that low doses of glyphosate
are harmless, their claims no longer have any valid scientific evidence. To the contrary, the knowledge that
glyphosate is non-monotonic and an endocrine disruptor makes it all the more
probable that it does cause substantive harm.
What’s the next step towards proving this? Well, how did people first find evidence that
tobacco caused lung cancer? Through
epidemiological studies and correlations!
The tobacco comparison is a story that deserves its own post, and will
get it. For now, it’s sufficient to note
that this is the importance of Swanson et al.
Through epidemiology, the paper builds a prima facie case for supposing that glyphosate could indeed cause
the rise of certain chronic disease conditions in America. Given that we now know what toxicology can
and can’t prove, Swanson et al.’s claims can no longer be dismissed with
blanket denials--they must be further
investigated. And however that
investigation turns out, we’ll still be able to tell GMO defenders that their claims
of pesticide safety aren’t worth the paper they’re written on.
Reference: “Genetically engineered crops, glyphosate and the deterioration of health in the United States of America” by Nancy L. Swanson, Andre Leu, Jon Abrahamson and Bradley Wallet, Journal of Organic Systems, 9(2), 2014 (http://www.organic-systems.org/journal/92/JOS_Volume-9_Number-2_Nov_2014-Swanson-et-al.pdf).
Reference: “Genetically engineered crops, glyphosate and the deterioration of health in the United States of America” by Nancy L. Swanson, Andre Leu, Jon Abrahamson and Bradley Wallet, Journal of Organic Systems, 9(2), 2014 (http://www.organic-systems.org/journal/92/JOS_Volume-9_Number-2_Nov_2014-Swanson-et-al.pdf).
Some interesting concepts here. I scanned through the Swanson et al paper, but I won't pretend I understood it all. However, it seems clear that correlations exist. As you pointed out, causation remains to be proven, but correlation is normally enough to justify further research. I think it will be interesting to see this moved through the rest of the scientific process.
ReplyDeleteAs a side note, I'm looking forward to seeing EPA's position on NMDR curves as they relate to endocrine disruptors. I know a lot of people don't put much faith in government bureaucracies, and they certainly move slower than molasses in January, but they certainly ensure the thoroughness of their evaluation.
No problem, Kent, I'll walk you through it in the course of the next few posts. Glad you accept it demands further looking into--that's all the authors claim! Yes, I too would like to see EPA's position on it, but have they said they are going to take one? Not to the best of my knowledge. You're right about molasses. Supposed to be a National Academy of Sciences report on GMOs etc. actually scheduled--for 2016!
DeleteHi Derek,
ReplyDeleteThat glyphosate is likely to be harmful even at low doses is a big part of why the findings of a study like this one are so important.
http://sustainablepulse.com/2015/02/12/pennsylvania-researchers-discover-glyphosate-herbicide-honey-soy-sauce/
That led me to cite one of the same studies you cite here in my most recent news summary.
https://attempter.wordpress.com/2015/02/20/gmo-news-summary-february-20th-2015/
These studies and the state of the science they establish for endocrine disruptor toxicology would be sufficient to blow out of the water even non-corrupt EPA tolerance levels. Of course EPA limits are tendentious anyway and meaningless other than as a gauge of how much poison the corporations expect to sell, since the EPA mechanically raises the levels in response to corporate petitions.
Russ
Wow. Do you see where this argument leads?
ReplyDeleteThe author makes the case that the effects-to-dosage toxicity of substances can be non-linear; and that in cases we even find "U"-shaped curves, where toxicity is high at high dosages, low at medium dosages, but then high again at low doses.
Note that while he's ostensibly talking about glyphosate toxicity, this could be equally true for all substances; and why not consider this when evaluating benefits as well as toxicity?
With this view of things, how can we assess anything with confidence? How can we decide what doses are low, medium and high? When do we decide we trust a substance to be safe (or beneficial), when someone can always argue that a dosage lower than what we evaluated might prove to be highly toxic (or have completely different benefits) than our spectrum of tests revealed?
Assuming there are substances with toxicity and/or benefits that behave this way, we need a whole new paradigm for evaluating effects. Simply saying we can't trust safety or benefits thresholds set using a linear model is in invitation to total paranoia. If our old model can't be trusted, its only fair to ask for a new model that can.
Until a new methodology is put forward, all this argument does is mess with our heads.
"we need a whole new paradigm for evaluating effects."
DeleteThat's exactly what Vandenberg et al. say in their article. That's just a fact of life. I wish I could find such a methodology, but that's way above my pay grade, so I'll leave it to those who can--and will!