No one likes weeding, and, for many years, people have been trying to find chemicals to speed the work without damaging themselves or the environment. One of the most popular weedkillers at present is Roundup, a product produced by Monsanto with glyphosate as the active ingredient. Promoted as being of low toxicity to humans and safe for the environment, the claims have been disputed by others.
Dangers to Humans
Studies have shown Roundup to be of very low toxicity when taken by mouth or by skin absorption. If a large quantity were to be ingested, by drinking it straight from the container for instance, symptoms would include breathing difficulty, low blood pressure, irritation of mouth and throat, nausea and vomiting, diarrhea, headache, dizziness and weakness.
Dangers to the Environment
Glyphosate itself is slightly toxic to birds and aquatic invertebrates but almost non-toxic to fish, though the formulation as Roundup may be more toxic to fish because of other ingredients. It seems to be nontoxic to honey bees.
The concern with most herbicides is persistence in the environment, with the potential to continue killing plants and causing damage to animals. Persistence in the soil is measured by "half life," the time in which half of it is broken down by soil microbes and other processes. The half life for glyphosate is between one and 174 days. In pond water, the half life is 12 days to 10 weeks.
In plants, glyphosate can be carried throughout the tissues, including roots. Some plants break it down quickly, in others it persists.
Very little of the chemical is carried by runoff from rain or watering because it adheres to soil particles strongly. If it gets into a lake or pond, it also adheres to the organic matter and soil particles suspended in the water.
As with most chemicals, Roundup has been the focus of a number of disagreements about research methods and conclusions drawn. Since the studies used to prove its safety for EPA approval were paid for by Monsanto, some claim that they were biased in certain ways. Roundup is listed as "dangerous to the environment" by the European Union.
In a recent study at the University of Caen in France, researchers found that an inert ingredient in the formulation, polyethoxylated tallowamine, or POEA, was more damaging to human embryonic cells than glyphosate itself.
There is also disagreement over the long-term effects of Roundup in the environment, something difficult to research since it has been in use for no more than forty years. Unexpected effects may be found in the future.
As with most chemicals, it is probably best to use it only when absolutely necessary and only in minimum amounts.