A new study by toxicologists and obstetricians looks in the bloodstreams of a sample of Canadians for pesticides associated with genetically modified foods (new acronym alert: PAGMF).  They studied pregnant women, their fetuses (actually umbilical cord blood after delivery), and also a group of non-pregnant women.  GM-associated insecticide was widespread in the blood samples; GM-associated herbicide was present but rare.

Some background: the overwhelming majority of GM crops grown in the world today are either herbicide tolerant (HT) or insect resistant (IR).  Herbicide tolerance is from a gene for immunity to glyphosate (Roundup) or gluphosinate (Liberty) weedkiller, allowing the farmer to spray weeds without harming the crop. Insect resistance is via a gene from the soil microbe Bacillus thuringiensis (Bt) which produces an insecticide — hence the name “Bt crops.”  Canada mainly grows a lot of HT canola, but it grows other GM crops too including some Bt maize (details here).

Bt insecticidal proteins were found in the blood of 93% of the pregnant women and 80% of the fetuses.  The current thinking is they get into humans via meat from animals fed Bt crops — these proteins have been found in the guts of pigs and calves.

Evidence of weedkiller in the blood was much more scant.  None of the samples from pregnant women or fetuses were contaminated; 5% of nonpregnant women had glyphosate and 18% had gluphosinate.

What does this mean for health impacts?  Nobody knows.  There are some signs that high levels of glyphosate and gluphosinate disrupt fetal development, but the levels in the women in this study were low.  I know of no evidence that Bt proteins in the blood are harmful, and Bt is quite safe for humans in most contexts.  (And as one of our graduate students just suggested, we should look on the bright side — the babies should be protected from caterpillar bites.)  But there’s no contesting the authors’ conclusion: “Given the potential toxicity of these environmental pollutants and the fragility of the fetus, more studies are needed.”  A lot more.

Should this affect what we eat?  Or what we think about GM crops? Ah, as with so many things, it all depends on the counterfactual — i.e., what you compare it to.  You can buy organic produce that is free of weedkiller, and organic or most grassfed beef will be Bt-free.  You pay more for these foods, but then again they offer benefits beyond the avoidance of pesticides.

On the other hand, while low levels of Roundup in adult blood and the common occurrence of Bt in fetal blood may give us pause, try wrapping your mind around some of the findings on other pesticides.  Start with this article by Rauh et al. that just came out in Environmental Health Perspectives. They have been studying the effects of exposure to chlorpyrifos in the womb.

Spraying chlorpyrifos on lentils in Andhra Pradesh, India. Photo by the kids of the Kalleda Photo Project.

(Chlorpyrifos is a common organophosphate insecticide, sold under many named including Dow’s product Lorsban.  It is used on food crops in dozens of countries and it is a big favorite of the farmers I study in southern India, who use it on cotton and also food.)

Years ago Rauh et al. started looking at umbilical cord blood for chlorpyrifos in several hundred births.  They found some problems right off the bat — for example, the babies whose mothers had chlorpyrifos in their systems were smaller.  They checked the kids at 3 years, and found the chlorpyrifos kids had cognitive and behavioral problems.  Now the kids are 7 and this new study shows the exposed kids to have slightly lower IQ’s and poorer memories.

The spread HT crops into Canada and several other countries has not reduced weedkiller use — actually it has led to increases especially in the use of Roundup, but also to less use of other more toxic sprays.  The spread of Bt crops has reduced the use of chlorpyrifos and many other toxic insecticides, but we now know it means most babies (in Quebec anyway) are born with Bt in their blood.  What that means for our health and our  babies, we really don’t know, but it’s hard to resist the conclusion that it’s better than organophosphates in the blood, and worse than neither.