Nanotechnology Risk to Soil Health

Overview: Nanotechnology and its application to agriculture and food

The application of nanotechnology techniques and engineered nanoscale materials (ENMs) to agricultural inputs is one of the means proposed for the “sustainable intensification” of agricultural crop production. The United Nations Food and Agriculture Organization (FAO) uses this term to describe techniques to increase yield in internationally traded crops to feed the project nine billion global population of 2050.

Despite the current lack of nanotechnology specific risk assessment metrics, and nano-specific mandatory regulation, a FAO/World Health Organization expert report stated, “It is expected that nanotechnology–derived food products will be increasingly available to consumers world-wide in the coming years.” According to a soon to-be-published 2013 Center for Food Safety (CFS) inventory, there are about 300 food or food-related products whose manufacturers claim to incorporate ENMs. Furthermore, “scientific patents and publications on nanomaterials in fertilizers and plant protection have increased exponentially since the millennium shift.”

The arguments for ENMs in fertilizers seem compelling. The atomic to molecular size of ENMs, in theory, would enable nano-encapsulated fertilizers to more effectively deliver plant nutrients to nano-sized plant pores. Less fertilizer would be leached into the soil and/or volatilized to become a greenhouse gas.

Most applications of ENMs and nanotechnology techniques to agricultural inputs are in the research and development stage. However, scientists believe that ENMs already in use for consumer and industrial products will reach ecosystems. Probably the greatest current nanotechnology-related risk to soil health comes from two sources of incidental contamination.

The first source is acknowledged in the National Nanotechnology Initiative’s (NNI) 2014 draft strategic plan: migration to the soil via water of ENMs from nano-coated consumer and industrial goods put in landfills, especially electrical parts. The second source is the treated sewage waste (“biosolids” in Environmental Protection Agency terminology) applied at least annually to at least 70 million acres of U.S. agricultural land. IATP commented on the failure of the draft strategic plan to recognize the risk posed by fertilizing agricultural fields with ENM-laced biosolids.

As a Purdue University researcher recently noted, “Land application of biosolids is standard procedure now [...]. If any of that [biosolid] contains nanotubes, that could be a problem.” Carbon nanotubes, configured by chemical and irradiation processes from one-atom-thick sheets of graphene, are the hardest and strongest materials known. Presently they are used in bulk to reinforce industrial parts, but there are a broad array of potential uses under investigation.

The crux of this problem for all bio-accumulating ENMs, particularly metal oxides and carbon nanotubes, is at least three-fold. First, ENM manufacture and incorporation into products is subject to 20th-century regulations. Second, ENMs entering wastewater streams, whether accidentally nor not, are processed by water treatment plants not designed to filter or treat ENMs. Third, the EPA regulation of biosolids is based on the pre-nano water treatment process, with no testing of the effect of ENMs on public health, farmworker health or soil health.

A laboratory experiment that computer simulated the wastewater treatment process in an anaerobic digester suggests that over a six-month period nano-silver particles would become a silver sulfide and less bio-reactive. However, these researchers acknowledge that further research on the effect of biosolids with silver nano-particles in field condition soil would be needed to show that the water treatment process had rendered the nano-silver particles less toxic.

The interface of ENMs and soil health is a major concern. Farmers are told to check their soil health at least annually. There is cause for concern that even if a farmer does not fertilize with biosolids, their soil could be at risk from nearby fields so fertilized. Although testing for basic nutrients in soil is not expensive, testing to detect ENMs in soil is and likely will be. Since there is no law, much less a federal budget, dedicated to protecting soil health, until there is mandatory regulation of ENMs and their use, it is very well possible that a field near you is experiencing some of the effects described here.

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