Is glyphosate safe? The active ingredient of the world’s most widely used herbicide, Roundup, is arguably also one of the most contentious. After decades of believing it posed a risk only to plants, there are growing concerns over its effect on people. But the debate is far from settled.

While many studies claim that glyphosate is safe and environmentally friendly, others have linked it to serious health issues like cancer and called for a worldwide ban. We took a detailed look at the issue and provided answers to some of the key questions behind it.

What’s glyphosate?

Glyphosate is the active ingredient in many weedkillers. It was introduced by Monsanto in 1974, its patent expired in 2000 and now it is sold by various manufacturers.

It is one of the most widely used herbicides in the United States. People apply it in agriculture and forestry, on lawns and gardens, and for weeds in industrial areas. Some products containing glyphosate control aquatic plants.

Farmers spray it on fields before their crops emerge in spring, so the crops do not have to compete with weeds. Some also use it as a pre-harvest treatment to dry out crops and make them easier to harvest. The UK Soil Association says such use is risky, as it can increase glyphosate residues in food.

How widely is it used?

The use of glyphosate skyrocketed after seeds were genetically engineered to tolerate the chemical. Because these seeds produce plants that are not killed by glyphosate, farmers can apply the weed killer to entire fields without worrying about destroying crops.

In the US, more than 750 products contain it. In 2017 the European Union extended the license for use of glyphosate for five years, with a strong debate among EU countries. Sri Lanka banned the use of glyphosate in 2015 – though the tea industry opposes the ban. Colombia stopped aerial spraying of glyphosate in 2015 but then reintroduced it.

What happens to glyphosate in the environment?

Glyphosate binds tightly to soil. It can persist in soil for up to 6 months depending on the climate and the type of soil it is in. Glyphosate is broken down by bacteria in the soil. It is not likely to get into groundwater because it binds tightly to soil. In one study, half the glyphosate in dead leaves broke down in 8 or 9 days. Another study found that some glyphosate was taken up by carrots and lettuce after the soil was treated with it.

How extensive is human exposure to glyphosate?

Because of its widespread use, glyphosate is in water, food, and dust, so it’s likely almost everyone has been exposed. And human exposure, through food and water, will probably increase in tandem with the growing use of the weed killer, according to a 2016 study published in the journal Environmental Sciences Europe.

But little is known about the magnitude of human exposure because food and water are not regularly tested for glyphosate residue. However, a few years ago, researchers tested the urine of a small group of people across the United States and found glyphosate residue in 93% of them.

Which foods contain glyphosate?

The main foods that contain glyphosate are genetically modified (GM), glyphosate-resistant crops, such as corn, soybeans, canola, alfalfa and sugar beets.

One recent study found that all 10 genetically modified soy samples examined contained high levels of glyphosate residues. On the other hand, samples from conventional and organically grown soybeans did not contain any residues.

What’s more, many weed species are now resistant to glyphosate, which is causing more and more Roundup to be sprayed on crops.

What are some symptoms from a brief exposure to glyphosate?

Pure glyphosate is low in toxicity, but products usually contain other ingredients that help the glyphosate get into the plants. The other ingredients in the product can make the product more toxic. Products containing glyphosate may cause eye or skin irritation.

People who breathed in spray mist from products containing glyphosate felt irritation in their nose and throat. Swallowing products with glyphosate can cause increased saliva, burns in the mouth and throat, nausea, vomiting, and diarrhea. Fatalities have been reported in cases of intentional ingestion.

Pets may be at risk if they touch or eat plants that are still wet with spray from products containing glyphosate. Animals exposed to products with glyphosate may drool, vomit, have diarrhea, lose their appetite, or seem sleepy.

Is glyphosate likely to contribute to the development of cancer?

Animal and human studies were evaluated by regulatory agencies in the USA, Canada, Japan, Australia, and the European Union, as well as the Joint Meeting on Pesticide Residues of the United Nations and World Health Organization (WHO).

These agencies looked at cancer rates in humans and studies where laboratory animals were fed high doses of glyphosate. Based on these studies, they determined that glyphosate is not likely to be carcinogenic. However, a committee of scientists working for the International Agency for Research on Cancer of the WHO evaluated fewer studies and reported that glyphosate is probably carcinogenic.

Can it be worse for those heavily exposed to glyphosate?

Evidence is mounting that people who are heavily exposed to it — farmworkers and landscapers, for example — have an increased risk of non-Hodgkin lymphoma.

A review led by University of Washington scientists published found that agricultural workers who used a lot of glyphosate had a 41% higher risk of contracting non-Hodgkin lymphoma over their lifetimes than people who used it infrequently or not at all.

On average, about 2 out of every 100 Americans develop non-Hodgkin lymphoma. For people who are highly exposed to glyphosate, the disease rate jumps to 2.8 per 100. That means they still have a relatively small chance of contracting the disease, but their risk is substantially higher because of glyphosate use.

Are there other negative effects?

There are hundreds of different types of microorganisms in your gut, most of which are bacteria. Some of them are friendly bacteria and are incredibly important for your health.

Roundup may negatively affect these bacteria. It blocks the shikimate pathway, which is important for both plants and microorganisms
In animal studies, glyphosate has also been found to disrupt beneficial gut bacteria. What’s more, harmful bacteria seemed to be highly resistant to glyphosate.

One article that received a lot of attention on the internet even hypothesized that the glyphosate in Roundup is to blame for the increase in gluten sensitivity and celiac disease worldwide. However, this needs to study a lot more before any conclusions can be reached.

If I use glyphosate products, what precautions should I take?

Carefully follow label instructions and warnings. Wear gloves and don’t let the chemical come in contact with your skin, clothing or eyes. Use it only on calm, rain-free days to prevent drift. Do not let it run off into waterways or gutters. Pets and people should wait until treated areas are dry before entering them