Organic Agriculture Wrongly Accused As Prominent Cause Of Heavy Metal Accumulation In Soil

Environmental Heavy Metal Contamination Image

via University of New South Wales

Yellow journalism is expected from supermarket tabloids and local television news casts, but the once venerated Slate shocked with a recent headline. "Rusted Roots: Is Organic Agriculture Polluting Our Food With Heavy Metals?" it screamed. The article hardly gets started before it's obvious that the author, James E. McWilliams is stretching a bit too far to make the connection that organic agriculture is causing heavy metal contamination in food. McWilliams writes that, "One issue frequently overlooked in the rush to embrace organic agriculture is the prevalence of excess arsenic, lead, cadmium, nickel, mercury, copper, and zinc in organic soil." While it's true that organic soil can contain these heavy metals, it's not true that this is something that is overlooked.

Organic farmers are a dedicated bunch. They're in the business of regenerating the soil as much as they're in the business of growing food and no organic farmer is going to "overlook" heavy metals in their soil. The Organic Materials Review Institute (OMRI), the non-profit organization tasked with deciding which input products are allowed for use in organic production and processing, published a study focusing on the problem in 2005 called Heavy Metals in Fertilizers Used in Organic Production (pdf). Hardly an overlooked issue any way you look at it.

But, the larger point that McWilliams does his best to sidestep is that even if certain types of organic inputs add heavy metals to the soil they are a minute fraction compared to metals added by industry, mining, vehicles, and conventional agriculture. Brian Baker, the research director at the OMRI, and co-author of the above report was interviewed by McWilliams and has since written a response to the published article.

When McWilliams interviewed me for his story, I emphasized that although organic was not immune to heavy metal contamination, the problem faced by organic farmers paled by comparison with conventional agriculture. Farmers who are not organic can and do use all fertilizers and soil amendments used by organic farmers. In addition, non-organic farms apply other fertilizers and soil amendments prohibited in organic farming that can be heavily contaminate with heavy metals, such as sewage sludge and industrial by-products. I also pointed out that rather than denying there was a problem, the organic community was dealing with it. McWilliams didn't mention any of that.

Even in his admission that there are other causes of heavy metal contamination McWilliams throws a shot at organic agriculture.

"Atmospheric deposition"--the transfer of pollutants from the air to the earth--has nothing to do with organic practices per se but is, rather, the result of industrial processes beyond the farmer's control.

Whew! At least it's not all organic agriculture's fault.

But it doesn't stop there. McWilliams concludes his article stating that "complete despair may still be avoided." His despair stopping solution? A genetically modified fern that, once scientists actually get around to perfecting it, will be capable of "sucking up zinc" which can then be "recycled and put to better use." Thankfully organic farmers, and soil and plant scientists, aren't waiting around for the lab results, they're out in the field working on solutions, including using mycelium fungus to decontaminate soil.

Brian Baker concludes.

Heavy metal contamination is not a simple function of amount or loading. Soil pH, cation exchange capacity, and nutrient levels also are factors in determining plant uptake. These are problems all farmers face. Just because people have higher expectations of organic farmers doesn't mean that they should be singled out.

Blaming organic agriculture for heavy metal contamination in food is blaming the victim for the crime.

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