What is ragweed and what are its consequences?
Common ragweed is a weed that thrives in:
- certain agricultural crops such as sunflower or maize, where it causes considerable yield losses;
- other environments such as riverbanks or roadsides.
Ragweed releases a highly allergenic pollen that causes the same symptoms as other types of pollen in allergic individuals suffering from rhinitis (sneezing, blocked nose, conjunctivitis, redness, swelling of the eyelids, etc.), severely affecting their quality of life. In France, the pollen peak occurs between mid-August and mid-September.
Development of ragweed in France and factors determining its spread
Originally from North America, ragweed was introduced into France during the Second World War through the transit of goods and people. 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.
Maps showing the distribution of ragweed in France from 2005 to 2017
Its spread is favoured by certain human activities: the transport of ragweed-contaminated soil or seeds, agricultural and/or mowing machinery, animal feed, etc.
Controlling the spread of ragweed through an integrated management strategy
ANSES has estimated different ranges of annual costs of ragweed's health impact at national level:
- cost of medical care (e.g. medicines and consultations), between 59 million and 186 million euros per year;
- cost of production losses based on absences from work, between 10 million and 30 million euros per year;
- cost of lost quality of life for allergic individuals, between 346 million and 438 million euros per year.
These costs are expected to increase in the future, due to the predicted expansion of ragweed-infested areas, thereby exposing new populations, and an increase in pollen levels in ambient air, mainly due to climate change. Strict control of the plant's spread is therefore necessary to limit the negative health consequences of ragweed.
Coordinated action to limit the spread of ragweed
Following its expert appraisal, ANSES finds that ragweed management is still confronted with certain regulatory obstacles, such as the limited enforcement power of local mayors, particularly on private land. It is issuing the following recommendations:
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 and protect the health of the general population and exposed workers.
- expand and intensify monitoring of the plant and its pollen on a national level;
- modernise the monitoring system for ragweed pollen by coupling it to models that can predict its dispersion throughout metropolitan France.
- 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;
- foster information exchanges between regions through the development of networks of doctors and "sentinel" patients.
Did you know?
In France, nearly a third of adults suffer from pollen allergy (ragweed, grasses, etc.).
There are two stages in the 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).
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:
- pollen in outdoor air (2014);
- mould in indoor air (2016);
- pollen and mould in the ambient air of France's overseas territories (2017);
- mould in outdoor air in France (2020).