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Genetically engineered crops – are they safe?

A pigweed (Amaranthus palmeri) prevalent in genetically engineered cropping systems that has evolved resistance to the commonly used herbicide glyphosate. (Photo credit: R. Chandran)

Major row crops, such as corn, soybeans and cotton, are genetically engineered to tolerate pests, such as weeds and insects. These crops are able to tolerate herbicides but will kill weeds and/or are able to kill insects upon feeding on crop parts. Undoubtedly, these modern technologies are essential to keep up with the increasing demand for food and fiber; however, the safety of GE foods to human health, the environment and socio-economic implications are vital for their long-term adoption.

A consumer is often bombarded with mixed messages regarding the safety of GE foods. Claims and viewpoints related to the positive and negative effects vary widely. The National Academy of Sciences appointed a committee to perform a rigorous and scientific review of available information to address food safety, along with its environmental and socio-economic aspects. Their findings were released during the summer of 2016 in a 584-page report.

Findings

The committee felt comfortable expressing that GE crops posed no adverse effects on human health directly, based on reasonable evidence generated by a large number of animal feeding studies. Livestock health was also not affected by consumption of GE crops. Based on examination of epidemiological data related to the incidence of cancers and other human health problems, they found no substantial evidence indicating that foods derived from GE crops were less safe than that from non-GE crops.

Although the impact of GE crops related to environmental aspects is more complicated, the committee was not able to pinpoint any adverse effect to the widespread use of such crops. The plant biodiversity in fields where GE crops were grown was not lower than those where non-GE crops were raised. In fact, there was evidence of higher levels of insect biodiversity on farms where Bt crops were planted compared to those treated with synthetic insecticides. The socio-economic effects of GE crops have been positive overall, based on the findings of this committee. In general, farmers benefitted from the availability of GE crops; however, small farmers faced certain challenges.

Despite modest yield gains, there are damaging levels in the buildup of resistance among various pests. For instance, in West Virginia there are weeds, such as Palmer amaranth (Amaranthus palmeri) and giant ragweed (Ambrosia trifida), that have evolved resistant to the herbicide glyphosate in parts of the state were herbicide-resistant crops have been grown for several years (Figure 1). Also, certain corn rootworms (Diabrotica spp.) have developed resistance to proteins produced by Bt corn intended to kill such insect pests in other parts of the country.

It appears that this technology has become a mainstay in modern agricultural systems. Public acceptance of this technology may depend upon rigorous testing of the safety related to this technology, and a sound scientific understanding of its intended and unintended consequence, and any potential hazards.

The methods by which GE crops will be developed in the future are expected to be less aggressive compared to how they were developed in the past. With a better understanding of the underlying principles, scientists are now able to edit genes within closely related species to generate desirable traits as opposed to introducing them from unrelated species.



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