Safety of pesticide-producing gene debated

By TOM CALLIS

Tribune-Herald staff writer

Pesticides are nothing new to agriculture.

But with the advent of genetic engineering, crops can now be made to produce their own bug-killing proteins, prompting questions over the ethics and safety of these modified plants.

The pesticide-producing gene was introduced in 1996 and allows farmers to get away with using less chemicals, biotech supporters say.

They also maintain it’s safe, noting approval from the federal regulatory agencies such as the U.S. Department of Agriculture, Food and Drug Administration and Environmental Protection Agency.

Still, the use of the gene has some consumers worried, particularly since it’s in such a widely used crop as corn.

So what is this gene and where does it come from?

The insecticidal protein kills certain insects that try to eat the crop by binding to cell receptors in the bug’s gut, causing death through cell disintegration. (Essentially, causing them to ooze to death.)

The protein is produced by a gene from the bacterium Bacillus thuringiensis. The bacteria — Bt, for short — can also be used as an organic pesticide for its pest-killing properties.

While regulatory agencies have concluded it is safe for human consumption, a 2010 study by scientists in Canada has helped to spread some doubt in those conclusions among transgenic critics.

Their study, which also looked at herbicides associated with some transgenic plants, took blood samples from 30 pregnant women, including samples from umbilical cords after birth, and 39 non-pregnant women in Quebec.

With Bt, it concluded that the protein was traced in 93 percent of pregnant women, 80 percent in fetal blood samples and 69 percent in non-pregnant women. Levels didn’t exceed roughly 0.2 nanograms per milliliter.

“… (Bt) are clearly detectable and appear to cross the placenta to the fetus,” the study said.

That study has helped fuel the debate over the practice of putting pesticides in crops, though it has been heavily criticized by other scientists who say the protein is also naturally occurring, and it’s unclear if what the study detected came from transgenic crops.

“Most of us who read the paper just shake our heads,” said Bruce Chassy, a professor emeritus of food and nutritional sciences at the University of Illinois.

Chassy, who has publicly criticized such research, said the results were likely false positives, noting that protein breaks down during digestion. Even if it didn’t, he said, they wouldn’t cause any harm since humans lack the same cell receptors as insects.

“We can eat grams and grams of Bt protein without any effect,” Chassy said.

Brian Federici, a professor of entomology, microbiology, and genetics at the University of California-Riverside, agreed.

“If any of the different Bt corns were harmful, we would know that by now and they would not be on the market,” he said in an email to the Tribune-Herald.

“The human stomach is highly acidic and virtually all proteins are rapidly degraded into amino acids and short peptides once they enter the human stomach.”

Aziz Aris, one of the scientists behind the Bt study, didn’t return an email requesting comment.

Scientists critical of transgenic research worry there isn’t enough known about what effects could be produced.

“We are introducing genes and putting them together in ways that have never been done before,” said Hector Valenzuela, a vegetable crops extension specialist with the University of Hawaii at Manoa.

“This could be benign,” he added, “it could (have impacts) years down the road.”

Email Tom Callis at tcallis@hawaiitribune-herald.com.