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Updated on 06/07/2021

Ragweed and allergies

Keywords : Ragweed, Pollens, Allergy, Biological pest control

Between 1 and 3.5 million people in France are believed to be allergic to ragweed. Pollen from ragweed, an invasive plant originally from North America, has a major impact on the quality of life of allergy sufferers, causing sneezing, nasal congestion, conjunctivitis and redness or swelling of the eyelids. According to ANSES, the medical care associated with these allergies may cost between €59 million and €186 million per year.  The Agency is involved in preventing and managing its spread. It makes recommendations to optimise the monitoring of this pollen and raise awareness of its effects on health.

Allergies with a particularly high impact

The number of people suffering from allergies has more than doubled in the last 20 years. Today, nearly one in three adults in France are allergic to pollen.

In an expert appraisal published in 2014, ANSES demonstrated that ragweed pollen is among the most problematic in France. This is because it is highly allergenic: it can cause a person to develop an allergy and can also induce allergy symptoms. Only five pollen grains per cubic metre of air are needed to trigger symptoms!

Allergies caused by ragweed pollen occur late in the season, with pollination peaking between mid-August and mid-September. 

Did you know?

There are two stages in an allergy:

  • A first stage in which the body responds to the presence of the allergen without triggering any symptoms. This is referred to as allergic sensitisation.
  • A second stage characterised by the onset of symptoms when the allergen comes into contact with the mucous membranes (mouth, nose, eyes).

There are several species of ragweed within the genus Ambrosia. The best known and most widespread is the common ragweed (Ambrosia artemisiifolia L.). But there is also the giant ragweed (Ambrosia trifida L.), western ragweed (Ambrosia psilostachya DC.) and lacy ragweed (Ambrosia tenuifolia Spreng.)

An exotic plant whose spread is accelerating

A native of North America, common ragweed was accidentally introduced into France in the 1860s with the importation of red clover seed from the United States. Initially present in the Rhone Valley, its spread has accelerated since the 1960s. The plant is now found in many parts of France, with varying levels of infestation. There are three main types of infestation areas:

  • areas with heavy infestation/establishment, including the Rhône, Isère, Drôme, Nièvre and Cher départements;
  • "frontline" areas such as the Charentes, Côte-d'Or and Gard départements, located on the edge of the heavily infested areas;
  • areas that are currently affected very little or not at all, such as Brittany.

Its spread is favoured by certain human activities: the transport of ragweed-contaminated soil or seeds, agricultural and/or mowing machinery, animal feed, etc.

Common ragweed thrives in:

  • certain agricultural crops such as sunflower or maize, where it causes considerable yield losses,
  • other environments such as riverbanks or roadsides.

Risk analysis of the ragweed species A. trifida and A. psilostachya

At the European level, alien species may be regulated because they have an adverse impact on biodiversity and ecosystem services (Regulation (EU) No 1143/2014) or because they present a phytosanitary risk to crops (Regulation (EU) No 2016/2031). In order to include species on the list of invasive species in these European regulations, the European Commission needs a risk analysis. This was conducted by ANSES for two emerging species of ragweed in France and Europe: A. trifida and A. psilostachya.

The risks associated with these two ragweed species are very different. The ecological and biological characteristics of A. psilostachya and its long-standing but still very localised presence in Europe led to the conclusion that the risk of invasion and of new introductions of A. psilostachya in the current context is relatively low.

In contrast, the risks associated with A. trifida are much higher. An introduction from the area of origin would be difficult to control. Favourable ecoclimatic areas where crop systems conducive to its development have been established are broadly distributed in Europe. Great difficulties with control in non-agricultural environments and the allergenic nature of the pollen of this species make it a proven threat to human health and the environment that must be controlled.

Ophraella communa: could this beetle be used to control ragweed?

Ophraella communa is a beetle of the Chrysomelidae family of North American origin that feeds on plants of the Asteraceae family. This family includes ragweed, along with crops such as sunflower and Jerusalem artichoke.

The insect was first reported in Europe in 2013 on common ragweed plants in northern Italy and southern Switzerland.

In its work, ANSES concluded that the risk presented by O. communa to sunflower and Jerusalem artichoke crops, and more generally to the environment, was acceptable. However, as O. communa may also consume sunflower and/or Jerusalem artichoke plants, the Agency called for caution regarding its use as a biological control agent through mass releases. It recommended that its introduction should not be prevented, but should be monitored.

Quantifying the health impacts of ragweed

In 2020, ANSES estimated the costs of the health impact associated with ragweed at a national level:

  • the cost of medical care (e.g. medicines and consultations) may be between €59 million and €186 million each year,
  • the cost of production losses based on absences from work may be between €10 million and €30 million per year.

These costs are expected to increase in the future, due to the predicted expansion of ragweed-infested areas and an increase in pollen levels in ambient air, mainly as a result of climate change.

Coordinated action to limit its spread

Regarding prevention and control:

  • Immediately introduce specific and locally coordinated regulations in the frontline areas, and in areas still relatively unaffected by the presence of ragweed. This should include appointment of a ragweed advisor responsible for implementing control measures on the ground.
  • Involve the building and public works sector more closely, alongside the agricultural sector, in order to raise awareness of the existing risk and promote the adoption of good practices (cleaning of machinery, management of contaminated land, etc.) in order to curb the spread of ragweed.

Regarding surveillance:

  • Modernise the monitoring system for ragweed pollen by coupling it to models that can predict its dispersion throughout metropolitan France.

Regarding information:

  • Raise awareness among healthcare professionals and allergic or potentially allergic individuals, in areas where ragweed is present and in those where it is likely to develop.

ANSES's work on biological air contaminants

For several years now, ANSES has been studying biological contaminants (pollen, mould, etc.) found in air to assess their health impacts on exposed populations. This includes the following work: