Microscopic fungi found in nature and in the air outdoors, molds cause respiratory effects, especially among children. An expert appraisal carried out by ANSES highlights a proven risk of asthma in this at-risk population and recommends improving surveillance in this area.

For several years, increasing attention has been paid to the effects of pollution of indoor and outdoor environments on health. In 2016, ANSES * published the results of its expert appraisal on mold in buildings, which constitutes a major public health issue because of its proven effects on respiratory health. As a result of this work, the agency then examined which molds, namely microscopic fungi, were present in the outdoor air (in particular Cladosporium, Alternaria, Aspergillus) and their effects on health. As with those found indoors, her expertise, which has just been unveiled, shows that they exacerbate asthma in children.

The agency reminds first of all that molds are microscopic fungi that colonize in particular soils and vegetation. They correspond to nearly 25% of biological contaminants in the air, which also include pollen, bacteria and viruses. In Europe, the total concentrations of mold in outdoor air are higher over the summer and autumn seasons extending from May to October and the lowest levels are found in winter between January and March, in connection with the cycle of plant life. "Cladosporium and Alternaria are present year round but in varying concentrations, the highest being in summer. », Notes ANSES.

Which molds are the most responsible?

Experts also say that “as mold growth in outdoor air is mainly related to climate and vegetation, reducing the main sources of mold growth is complex. The latter indicate that while the studies considered (29 in total) exploring the health effects of molds in the ambient air are few in number, their analysis revealed an association between short-term exposure and an exacerbation. asthma in children. However, they say the data are "too limited to conclude that there is an association between short and long-term exposure and worsening respiratory symptoms in adults." "

In the studies in question associations were tested between exposure to molds in the ambient air and: emergency room visits or hospitalization for asthma, asthma symptom score, peak expiratory flow and use of treatment. asthma medications. It turns out that these "allow a conclusion only as to the exacerbation of asthma in children, with sufficient evidence to establish the existence of an association for total spores, ascospores, basidiospores. , Alternaria, Cladosporium, Coprinus, and a probable association but to be confirmed for Aspergillus / Penicillium and Botrytis in children. », Underlines ANSES in its report.

Better train health professionals

At the end of the expert's report, the authors of the document claim, however, that they were unable to define a concentration of fungal spores in the ambient air below which no health effect is expected for the general population. However, their conclusions highlight the fact that their effects on health are added to those of molds present in indoor environments, which are already the source of proven effects with regard to the development and exacerbation of asthma in children. In addition, the effects associated with mold in indoor environments could be extrapolated from exposure to mold in ambient air.

"Like exposure to pollen, exposure to molds, whether present in indoor or outdoor environments, is a public health issue, given the effects on respiratory health and the identification of population groups more particularly at risk such as children. It therefore appears useful and relevant to continue monitoring these microbiological agents in ambient air, in association with that of pollens throughout France. », Concludes ANSES. This encourages a more general study of exposure to other microorganisms (viruses, bacteria) present in the ambient air but also in connection with occupational exposure.

For its other recommendations, the Agency underlines the need to improve the monitoring of molds in outdoor air by optimizing the existing monitoring system, harmonizing analyzes and measurement periods or even disseminating information. mold information. It also advocates better training of health professionals on the health effects of mold in the outside air, in particular on the risks of exacerbation of asthma in children. Note that according to Health Insurance, asthma is the most common chronic disease in children and the leading cause of school absenteeism. In France, at least 10% of children suffer from it.