Pollen and mould in the ambient air of France’s overseas territories: improving our understanding in order to better assess their health impacts

ANSES received a request from the French Ministries of Health and the Environment to report on the state of knowledge concerning the pollen and mould of greatest concern to health in the ambient air of France’s overseas départements and regions, and the principal related health effects. This request followed on from the publication in 2014 by the Agency of an expert appraisal on pollen in the ambient air, and another in 2016 on mould contamination in buildings, in France.

Exposure of the general public to pollen and mould in ambient air

Aucun dispositif pérenne de mesures des pollens et des moisissures présents dans l’air ambiant n’existe actuellement dans les DROM. Les données présentées dans le rapport d’expertise ont permis de dresser une liste non exhaustive et d’estimer le potentiel allergisant des pollens (filao, euphorbe, canne à sucre, etc.) et des moisissures (cladosporium, aspergillaceae, etc.) présents dans les DROM. Elles mettent en évidence des variations qualitatives et quantitatives des pollens et des moisissures, en lien avec les facteurs géographiques et/ou climatiques. Toutefois, il s’agit de données ponctuelles et très localisées qui ne permettent  pas de dresser un inventaire précis des espèces présentes dans les DROM ou d’évaluer précisément l’exposition de la population à ces agents biologiques.

Health effects potentially related to pollen and mould in ambient air

The Agency found that cases of allergic rhinitis are more common in Réunion and Guadeloupe than in mainland France. The same was found to be the case for asthma: the number of people with asthma, and the morbidity and mortality related to asthma, are higher in Guadeloupe, Martinique and Réunion than in mainland France. For example, asthma is more prevalent among junior high school students in the overseas départements (Réunion and the French Caribbean) than the national average (between 11% and 12% in these overseas territories compared with 8.6% in mainland France). However, these data are not sufficient to establish a link between these pathologies and exposure to pollen and mould in the ambient air.

In addition, the absence of specific and reliable allergy tests makes it impossible to diagnose the sensitivity of the population to pollens and moulds characteristic of the DROMs.

Factors interacting with pollen and mould

In the current state of knowledge, it is not possible to determine the influence of weather conditions or atmospheric pollution on the production of pollen, the development of mould or their dispersion in the ambient air of the DROMs.

As this concerns mould in tropical environments, their development and dispersion in the ambient air are a priori favoured by certain factors: relative humidity, rainfall, temperature, wind, tropical cyclones, etc.

Although health indicators are clearly affected by sand haze, air pollution and certain weather or climate conditions, it is not possible, in the current state of knowledge, to assess the interaction between these factors and the pollen and mould present in ambient air in the DROMs.

The Agency's recommendations

In the light of these findings, the Agency recommends assessing the exposure of the general population of the DROMs to pollen and mould by:

• setting up a scheme for measuring the pollen and mould in the ambient air, taking into account the distribution of the population, plant biodiversity and climate conditions. Measuring sensors should be installed, in priority, in the more densely populated areas, such as the urban environment;
• pursuing research and development for new methods of capture and analysis that would enable the identification of species specific to the DROMs.

The Agency recommends improving knowledge on the state of health of the population potentially exposed to the pollen and mould found in ambient air in the DROMs. Different avenues are proposed to achieve this: implementation of epidemiological studies, development of allergy tests specific to the pollen and mould found in the DROMs, and creation of a network of sentinel physicians.
 
It is also necessary to improve our knowledge of the factors that interact with the pollen and mould in the ambient air of the DROMs: in particular, this will involve determining the influence of weather conditions, climate change and atmospheric pollution on the production of pollen and the development of mould, and their dispersion in the ambient air. The Agency also recommends continuing research into other types of outdoor exposure, for example with studies to determine the physicochemical and biological characteristics of sand haze, and to identify its composition.

In addition, the Agency reiterates its recommendation to set up studies to assess the nature and abundance of mould inside buildings in the DROMs, first issued in the context of its expert appraisal on mould contamination in buildings, published in 2016.

Concerning plants that emit pollen of concern for health, the Agency recommends:

• limiting the cultivation of plants already known to be allergens in mainland France or other countries;
• in regional environmental health plans for the DROMs, applying Actions 8, 9 and 10, “for the monitoring, prevention and reduction of pollen and/or mould allergens in the air" included in the National Environmental Health Plan 2015-2019.

Lastly, the Agency recommends informing the population on pollen and mould as a preventive measure. It also advocates encouraging the establishment of a system for coordinating all the actors in the field (regional health agencies, associations accredited for monitoring air quality, physicians, pharmacists, biologists, botanists, etc.) in order to promote the emergence of common actions and the sharing of information on this health issue.