Dear EarthTalk:

What’s the current thinking on the safety of genetically engineered or modified products with regard to environmental, farm worker and consumer health?

A.J. Cary, NC

Few topics are as divisive as genetic engineering. Plants and animals that have had their genomes artificially altered now dominate the world of agriculture. The vast majority of U.S.-grown corn and soybeans are genetically engineered. In grocery stores, over 60 percent of processed foods contain at least some components derived from GMOs (genetically modified organisms). Given all this, it makes sense to ask whether or not these altered forms of life have deleterious effects on humans or the environment.

When it comes to human health, the evidence suggests GMOs are harmless. Exhaustive meta-analyses of scientific studies on GMOs have generally found no links between their consumption and negative health outcomes. However, there are some caveats. One is that the biotechnology companies responsible for the creation of GMOs have also been responsible for a large portion of the research on their health effects. Therefore, financial conflicts of interest may have tainted the research. Additionally, many scientists still feel that the jury isn’t out on the safety of GMOs. A 2015 scientific paper signed by 300 independent researchers from around the world states that the effects of GMOs on health remain “unclear.”

Another factor is that scientific studies on GMO-related health risks have generally been short term. We can’t extrapolate the effects of years of GMO consumption on human health by looking at the seemingly null results from a year-long study on rodents. It could still be that GMOs are causing health issues, but we’ve failed to establish a causal link because of how long these issues take to manifest. That said, it’s quite possible that most (if not all) GMOs on the market today are completely safe to eat. Regardless, testing should continue, especially for new varieties of GMOs that aren’t well studied.

Environmentally, GMOs are a mixed bag. Most crops are genetically modified in an effort to fight pests. There are two ways to accomplish this goal. The first is to create plants that produce pest-killing toxins “endogenously”: When pests eat such plants, they die. These types of GMOs can actually be good for the environment in that they often don’t require as many pesticides as unmodified plants.

Unfortunately, an alternate pest fighting strategy that also uses genetic modification—engineering plants to be resistant to pesticides and herbicides—has the opposite effect, generally leading to an increase in agricultural waste. Also of concern is the genetic contamination of wild species due to cross breeding with GMOs. This is particularly a risk in the case of GMO farmed salmon. If these fish escape fish farming operations and contaminate wild stocks, the ecological consequences could be severe.

All in all, GMOs are still shrouded in uncertainty. They seem to have some benefits, and many scientists believe they can help address world hunger. However, there’s still a chance GMOs could cause health issues, and they have already caused some environmental issues. If you’re not convinced by the research to date, and prefer to avoid GMOs altogether, look for the non-GMO project label on the foods you buy. 

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