A study conducted by Brazilian researchers found acute Roundup exposure at *LOW* doses (36ppm, 0.036g/L) for 30 minutes induced cell death in Sertoli cells in prepubertal rat testis. Are you saying that this study, and ALL studies that find safety issues with glyphosate, are baseless and wrong? Only Monsanto is right?

Expert response from Kevin Folta

Professor and Chairman, Horticultural Sciences Department, University of Florida

Wednesday, 14/08/2013 13:49

Short answer, note that the researchers used "Roundup", not the active ingredient glyphosate. It is sort of like saying water is toxic to cells because bleach is 95% water, and when they were incubated with bleach they died.

Roundup is a formulation of glyphosate plus a surfactant, in this case POEA. Surfactants are wetting agents, think of them as detergent-like. They help break surface tension on a plant's foliage so the active ingredients have better penetration. This way farmers can use less active ingredient.

The effects of POEA on cells in culture and negative impacts in aquatic environments are well described.

So it is no surprise that sensitive human cells in a dish will show symptoms and perhaps die when you put them in small amounts of detergent. So were the authors correct in saying that Roundup affects cells in a dish? Probably. Does this mean that glyphosate or roundup has effects on human reproduction? Not so much.

Similar studies have been published before by Seralini's lab. They showed using human cells in culture that Roundup affected them at high concentrations, but glyphosate alone did, well, not much.

Figure 8 of Claire et al shows a statistically significant 35% decrease in testosterone produced by cell cultures after 24 h in glyphosate or Roundup. At 1ppm there is an effect. As the compounds are increased, no significant effects are seen. In a pharmacological experiment we always perform such tests below the threshold of the response, as well as through a range of concentrations to show a dose-response relationship. The authors do not demonstrate this. In fact, the only concentration that has an effect is the lowest one. Increasing the concentration 100 fold shows no effect.

This is always curious to scientists. If you increase the dose, less effect is seen.

The other thing to keep in mind is that human beings are more complex than cells in a dish. Our exposure to glyphosate is minimal, as it is not sprayed on food products or even close to harvest. Glyphosate moves through the digestive tract rapidly, some is excreted in urine and what's left is broken down by a cytochrome in the liver. Even if glyphosate was dangerous, your testes would probably not see levels close to those observed in this report.

The studies that "find safety issues" are important because they begin to find evidence for how a compound may be dangerous. They are not all "baseless and wrong" but most have limitations promoters fail to consider. At best, they give a new hypothesis to test. That's good. However, you have to consider the limitations of the study. Frequently the authors do discuss how the effects seen translate into infertility, etc, even though that was never measured. That's bad science.

Glyphosate has been off patent since 2000, so Monsanto is not the only producer. Many independent studies have been done that show no effects at all in humans. Even people that try to kill themselves by drinking it wake up in the morning feeling queasy (but are weed free!).

Lastly, Mink et al 2012 has examined epidemiological data and there is no connection between glyphosate use and any cancers.

As glyphosate use increases and may continue to increase it is important to understand its effects on health and the environment. Many scientists are looking at this, as are concerned citizens. That's great. We just have to keep in mind the strengths and limitations of each study before we put too much weight into it. Thanks for the question.