Here below is the first paragraph of an article about Monsanto's "Roundup" weedkiller - a very widely used (the most widely used pesticide in the USA) and advertised product that "kills the root as well as the leaves". Glyphosate (click for Wikipedia article) is normally undestood to be the active ingredient. The article goes into concerns about the toxic effects of one of the so-called "inert" filler ingredients.
Glyphosate is represented as being sort of harmless because it is "inactivated on contact with soil" (or at least I remember that's what the adverts used to claim). One reason why environmentalists don't like Roundup is because Monsanto are one of the biggest forces behind the genetic modification of plants (GM crops - otherwise known as Frankenstein foods...) and they have genetically created plans which are "Roundup ready". What this means is that a farmer can plant a crop of these plants and then all they have to do is spray the field with Roundup and every single plant and weed that is not the GM crop will die. This has two problems. Firstly, Roundup may not be as benign as Monsanto paint it, although the research that suggests this is disputed (by Monsanto...). Secondly, and probably more worryingly, is that pollen from the GM crops can fertilise similar crops nearby. If those crops happen to belong to an organic farmer, who saves their seed, then that seed would have the Monsanto genetic material in them and the farmer may lose their organic certification and livelihood.
The GM technology has not got a completely clean bill of health yet. Even more worryingly, the Roundup resistant genes have already somehow spread to many weed species which means eventually that there will be no point in spraying with Roundup because the weeds in the crop will be resistant to the chemical! At that point, the farmer will be back where they started except their crops will have useless GM genes in them that may cause subtle, yet to be seen and researched, effects in the nutrition levels or even toxicity of the food crops. Not a win - win situation!
Here's the first paragraph:
Weed killer kills human cells. Study intensifies debate over 'inert' ingredients.
Used in yards, farms and parks throughout the world, Roundup has long been a top-selling weed killer. But now researchers have found that one of Roundup’s inert ingredients can kill human cells, particularly embryonic, placental and umbilical cord cells. The new findings intensify a debate about so-called “inerts” — the solvents, preservatives, surfactants and other substances that manufacturers add to pesticides. Nearly 4,000 inert ingredients are approved for use by the U.S. Environmental Protection Agency.
Click here for link to original article