Frankly, this assurance, the claim on the part of "experts" (those who are in the business) that they know what they're doing, is more often false than true, at least insofar as the implication is that they know all there is to know about the consequences of their beliefs, choices, and actions.
Which "experts" you ask. What business? It's an observation about people and the nature of knowledge, so it hardly matters, except as the stakes may be higher in some cases than in others. One such case is the set of practices collectively known as modern agriculture, which includes the use of GMOs, pesticides, herbicides, and concentrated fertilizers, and which, because it is applied over such a large area, can fairly be characterized as an experiment being conducted on the planet – the only planet we have.
In an article published on the Scientific American website, Professor Nina Fedoroff of the King Abdullah University of Science and Technology and Pennsylvania State University, states the following:
Most early alarms about new technologies fade away as research accumulates without turning up evidence of deleterious effects. This should be happening now because scientists have amassed more than three decades of research on GM biosafety, none of which has surfaced credible evidence that modifying plants by molecular techniques is dangerous.
On this point, Professor Fedoroff is clearly speaking from expertise, but notice that the issue she addresses is whether the process of modifying plants by molecular techniques is inherently dangerous, not whether specific modifications might be so. In the same paragraph, Fedoroff goes on to fume somewhat recklessly:
One scare story based on a bogus study suggesting a bad effect of eating GMOs readily trumps myriad studies that show that GM foods are just like non-GM foods.
Further on she states:
Herbicide-tolerant crops have made a major contribution to decreasing topsoil loss by facilitating no-till farming. This farming method reduces CO2 emissions from plowing and improves soil quality.
At this point I must express gratitude, for her having mentioned the advantages of no-till farming, but there are better ways to manage it than through the application of herbicides. There's the matter of reduction in yields when herbicides are applied and the plants must invest energy in resisting them. Also one must wonder how much attention has been given to the question of whether the genetic modification which provides plants with resistance might itself be problematic, perhaps resulting in byproducts which are toxic to animals and humans. Returning for a moment to an earlier passage, Fedoroff claims:
We can now use these methods to make precise improvements by adding just a gene (or two or a few) that codes for proteins whose function we know with precision.
This is blatant conceit. The proteins genes code for commonly have more than a single function in the development and/or physiology of an organism, and may also have collateral effects that wouldn't be termed "functions". To say that one knows the function of a protein "with precision" is to claim to to know all potential effects of that protein under all conceivable conditions. In her conclusion Fedoroff displays almost childlike naiveté regarding corporate veracity and commerce:
If the popular mythology about farmer suicides, tumors and toxicity had an ounce of truth to it, these companies would long since have gone out of business. Instead, they’re taking more market share every year. There's a mismatch between mythology and reality.
I do not suspect Professor Fedoroff of being a complicit apologist for industry, but I do suspect her of habitually misplaced trust.
