Roundup weedkiller probably causes cancer, says WHO study

The Monsanto product – the world’s most widely used herbicide – contains glyphosate, which may also be carcinogenic for non-Hodgkin’s lymphoma

Roundup, the world’s most widely used weedkiller, “probably” causes cancer, the World Health Organisation (WHO) has said.

The International Agency for Research on Cancer (IARC) – WHO’s cancer agency – said that glyphosate, the active ingredient in the herbicide made by agriculture company Monsanto, was “classified as probably carcinogenic to humans”.

It also said there was “limited evidence” that glyphosate was carcinogenic in humans for non-Hodgkin’s lymphoma.

Concerns about glyphosate on food have been widely debated in the US recently, and contributed to the passage in Vermont last year of the country’s first mandatory labelling law for genetically modified food.

The US government considers the herbicide to be safe. In 2013, Monsanto requested and received approval from the US Environmental Protection Agency for increased tolerance levels for glyphosate.

It is mainly used on crops such as corn and soybeans, which are genetically modified to survive it.

Why should I care about glyphosate?

Glyphosate is the world’s most widely produced herbicide, by volume. It is used extensively in agriculture and is also found in garden products in many countries. The chemical is an ingredient in Monsanto’s weedkiller product Roundup, and glyphosate has become more popular with the increasing market share of crops that are genetically engineered to be tolerant to the herbicide.

What evidence is there for a link between glyphosate and cancer?

The IARC review notes that there is limited evidence for a link to cancer in humans. Although several studies have shown that people who work with the herbicide seem to be at increased risk of a cancer type called non-Hodgkin lymphoma, the report notes that a separate huge US study, the Agricultural Health Study, found no link to non-Hodgkin lymphomas. That study followed thousands of farmers and looked at whether they had increased risk of cancer.

But other evidence, including from animal studies, led the IARC to its ‘probably carcinogenic’ classification. Glyphosate has been linked to tumours in mice and rats — and there is also what the IARC classifies as ‘mechanistic evidence’, such as DNA damage to human cells from exposure to glyphosate.

The weedkiller has been detected in food, water and in the air after it has been sprayed, according to the report from WHO. However, glyphosate use is generally low in and near homes where the general public would face the greatest risk of exposure, the report said.

The evidence for WHO’s conclusion was from studies of exposure, mostly agricultural, in the US, Canada, and Sweden that were published since 2001.

Sources:The Guardian ,Nature.com