We know this because the manufacturers tell us they are. It's pretty simple, they have tested them, they proclaim them as completely safe, therefore they are.
Let's look at these corporate leaders of bioengineering technology in a little more depth.
Monsanto, the first company to market genetically modified products has been in business for over a century. Their first product, saccharin for the Coca Cola company. They have existed mainly by manufacturing some of the worst chemicals known to mankind, from PCB's to DDT to Agent Orange to Dioxin. It isn't the manufacture of harmful chemicals that in itself is bad, it is the FACT that Monsanto attempted to save money by wholesale dumping of byproducts, used PCB's and other industrial wastes into lakes, streams, waterways and into settlement ponds to infiltrate the groundwater instead of correctly handling and disposing of such wastes. High temp incineration costs money, it's free to dump it into the water supply of local towns. Monsanto is directly responsible for 98 of the EPA Superfund Sites that have been in the cleanup process for nearly forty years now at a cost to American taxpayers of ten TRILLION dollars. Monsanto's contribution to cleanup of their illegal dumping, ZERO. Currently Monsanto makes money from GMO seed production, herbicides and other farm chemicals, the manufacture of the questionable hormone rBGH which is outlawed in most of the industrialized world, weather data services, and not to be discounted, but a significant amount of revenue comes from suing farmers for patent infringement.
Dow. is the largest manufacturer of industrial chemicals in the United States. They make some interesting things, napalm, nerve gas, a huge variety of plastics including styrofoam, and lately they have begun to buy up coal mining operations. At one time they made pesticides and are responsible for nearly a quarter of a million deaths due to equipment failures and the release of said pesticides into the heavily populated town of Bhopal India. To date, the company has refused to compensate a single person for losses of loved ones, pain suffering or anything related to the disaster. In the last ten years the EPA has begun an investigation into the decades of the company dumping dioxin into the Michigan waterways instead of using approved yet more costly disposal of the wastes. They are also being investigated for over 250 deaths from chloropyrifos poisoning at their manufacturing plant. Something they hid, and just compensated American workers to keep quiet about. Dow now makes Genetically Modified crops for farmers.
BASF is the largest manufacturer of industrial, commercial and consumer chemical products in the world. Not just old video tapes, but all kinds of plastics, pharmaceutical and farm chemicals. Huge ties to Fascist Germany and for three decades after the war virtually all of the senior management were former members of the Nazi party. The three manufacturing facilities in the US are rated as some of the worst in the world and since 2001 have been cited by the EPA 673 times for violations of environmental regulations. BASF now makes Genetically Modified crops for farmers along with a whole host of chemicals for farmers.
DuPont started out making munitions and explosives. Not a bad thing in itself, someone had to do it. The company has the dubious and grand designation as being the company that has the largest ever civil fine assessed by the EPA for violating Federal environmental laws. The company is responsible for 20 of the EPA superfund sites. Again, ten trillion dollars for the cleanup, money paid toward that cleanup by DuPont, ZERO. In 2013 DuPont has been targeted as the worst contributor to air pollution in the US. DuPont now makes Genetically Modified crops and farm chemicals.
Syngenta, was formed by the merging of the agrochemical divisions o AstraZeneca and Novartis. They make dozens of pesticides of which many are banned in their home country of Switzerland. Paraquat and Atrazine beng the most recognizable. Well, except for their neonicotinide pesticides that are now in the process of being banned in most EU nations. Syngenta is lobbying hard to block the ban and has even gone so far as to threaten to sue EU leaders that vote for the block. Syngenta is responsible for 18 of the US EPA Superfund sites and now produces Genetically Modified crops along with a whole host of agrochemicals.
These are the companies that control the destiny of food in the world today. Each of them has horrific pasts, and some are not so exceptional in the present and their track records have been filled with lies, deceptions and disinformation. Each of them tells us that their products are safe, each of them backs up their claims with short term feeding studies. The big question is do we believe them? When qualified scientists do comprehensive long term studies the results give us very different pictures.
Who do we believe?