Should wine drinkers worry about agrochemicals in wine?

Anti-GMO non-profit group Moms Across America made headlines earlier this year in the wine world. An anonymous individual commissioned a commercial lab to analyze 10 (yes, only 10) California wines for the presence of glyphosate, the active ingredient in several weed killers including the commonly used Roundup®. The lab reported detectable glyphosate concentrations in all 10 wines, including two produced in organic vineyards where glyphosate use is prohibited.

But here’s the important detail that most readers missed: the highest concentration detected was 18.74 parts per billion (ppb). The Environmental Protection Agency (EPA) regulates glyphosate residues in food. There is no limit set for wine, but the safe threshold for berries (including grapes) is 200 ppb. So even if the tested wines contained 10 times more glyphosate, they still would not have exceeded the limit for grapes.

If the above story sounds familiar, you might be thinking about the German beer industry where the same thing happened. Environmental activists submitted a small number of samples for analysis, and the trace amounts discovered were broadly reported. The industry response noted even if the analyses were accurate, an adult would need to drink 1,000 liters (about 264 gallons) of beer each day for the glyphosate to be considered a health risk.

These “studies” were tiny in size and do not meet the bar for peer-reviewed science. Nonetheless, what’s not clear is how glyphosate ended up in detectable quantities in the beer and wine. A range of explanations is plausible and include potential analytical errors, tampering of samples, herbicide drift, and use of the product beyond the regulated practices as denoted by the EPA. But it’s important to note that this is truly a mystery since glyphosate is sprayed on weeds under vines, not on the vines themselves. I’m unaware of any experiment that demonstrated grapevine uptake of glyphosate directly from soil.

We should be able to turn to the academic literature for some guidance on whether wine drinkers should be concerned about glyphosate, but there is false information being peddled there, too. A recent study published by the journal Food Chemistry reported an impact of glyphosate on fruit characteristics when compared to mechanical removal of weeds through cultivation. But the field treatments were applied at different times, the study reported on only a handful of vines and contained only one year of data. It should never have been published.

Why are environmental groups focusing on this weed killer? Certainly there is a strong argument that glyphosate is overused. But the reason that it has attracted the attention of many activists is due to its historic link with genetically modified organisms (GMOs). The first GMO crops were developed with the intention of being able to withstand glyphosate application so that weeds in the field would be easier to control. Since the early GMOs were touted as being glyphosate-resistant, glyphosate has become a prominent target simply by association.

But glyphosate is also used on non-GMO crops including grapes. Vineyards that use glyphosate do so to control weeds under the vines since it is generally considered to have low toxicity. While a wistful mix of plants throughout a vineyard may look romantic, weeds can compete with the vines for limited nutrients and water, leading to diminished vine health and eventual death.

Glyphosate use has its’ downfalls. My own research program at Cornell University demonstrated over a four-year period that when sprayed under vines it increased leaching of dissolved organic carbon (a proxy for soil breakdown) from the soil. It also caused more leaching of nitrogen – a groundwater pollutant. There is a long list of weeds that have now developed resistance to glyphosate due to its excessive use. And while there is considerable debate about whether glyphosate is a possible carcinogen, it’s unlikely that it is as harmless as was initially assumed.

Reflexively abandoning the use of glyphosate in vineyards could result in even worse environmental impacts. Unfortunately, the alternatives to glyphosate use in vineyards being touted by some environmental groups aren’t necessarily better -- and some are worse. Cultivation is a possible weed control alternative to herbicides but it can lead to soil breakdown and requires more frequent trips through the vineyard with heavy equipment, using more fuel and increasing greenhouse gas emissions. The safe, alternative herbicides to glyphosate, such as vinegar, soaps, and oils are not nearly as effective as glyphosate, again requiring many more trips through the vineyard, increasing the carbon footprint of the operation.

Unfortunately much of the agitation about glyphosate and wine can be directly attributed to bad science going viral. I’m not pro-glyphosate, but there simply isn’t enough good science to convince me to be anti-glyphosate, either. Before the court of public opinion rules on this matter, we need to wait for science to catch up and find the right answers. And in the meantime, I’ll keep drinking wine.

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