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A pollen monitor

Can I go out and enjoy a walk? In springtime, grass and tree pollen can be a real nuisance for hay fever sufferers, often ruining trips outdoors. The ability to precisely predict which weeks and which days are likely to be pollen-free would provide enormous relief to a great many people. Scientists at the Fraunhofer Institute for Physical Measurement Techniques in Freiburg, the University of Freiburg and the German Weather Service have developed a prototype device for analysing bioaerosols that enables precise pollen concentration forecasts to be made.

It would be extremely helpful to have a pollen concentration forecast along with the next day’s weather forecast. However, current forecasts for pollen remain somewhat imprecise. They are based on data gained from the manual analysis of pollen under the light microscope. “This method is work-intensive and time-consuming,” said Gerd Sulz, who supervises the project at the Fraunhofer Institute for Physical Measurement Techniques (IPM) in Freiburg. “Data that are analysed manually do not produce results quickly enough to allow us to make pollen status information available to hay fever sufferers in time.” Samples contain a lot of dirt and experts have to extract the relevant particles from the sample. In addition, the pollen are often dry, which makes it difficult to determine the type of pollen based on morphological details alone. Precise analyses usually take up to two days.

A fridge with a sensitive interior

Pollen monitor (Photo: German Weather Service)
In order to enable more precise and timely analyses, the German Federal Ministry of Education and Research (BMBF) founded a project, which ran from 2003 to 2006, eventually leading to the development of a pollen monitor prototype. This device, developed under the leadership of Gerd Sulz from the IPM, enables the automated and highly time-resolved analysis of bioaerosols in the air. The project also involved teams from the Institute of Computer Science at the University of Freiburg, the German Weather Service and representatives from industry. The results achieved are excellent even though the system looks like nothing more than a fridge. The pollen monitor houses a complicated technology, which is more precise and quicker than any human expert.
The pollen monitor is fully automated and is able to collect pollen particles from the ambient air via a high-volume stream of air (ca. 1000 litres/min.). The particles are deposited on a carrier that consists of a hydrous glycerine gelatine layer. As the temperature increases, the pollen become embedded in the glycerine gelatine layer where the pollen, once shrunk, are then re-hydrated. They are then ready to be analysed under the microscope, which is a masterstroke of computer-based image recognition. The system not only has to pick out soot or wire abrasion particles, but also has to be able to determine the relevant pollen in the three-dimensional gel, whatever their position in the gel.

Adaptive image recognition

The air-conditioned and shockproof pollen monitor houses a sensitive microscope that creates a three-dimensional image of the gel and the particle captured inside it. It also creates a fluorescent image. Because biological particles fluoresce in the UV range, a computer, which is connected to the microscope, is able to distinguish the pollen from a whole range of other particles. The pollen then have to be assigned to trees or grasses, a process that is somewhat complex.
Microscopic picture of different pollen species, which the pollen monitor determines automatically. (Photo: German Weather Service)
“The pollen species can be differentiated according to their morphological properties,” said Sulz. “The major challenge is to be able to automatically determine these characteristics regardless of their position on the carrier.” The computer divides the whole picture into many partial pictures of individual particles (e.g. pollen) and extracts their characteristic features on the basis of greyscale invariants. The result is a characteristic fingerprint that can be compared to already known tree or grass pollen fingerprints, based on information that the computer has previously learnt. The pattern of the new pollen is compared with the pattern of pollen stored in the database. A simple table lists the pollen species present in a particular air sample. The device then transmits the results to its operator via the Internet.

Components can be freely combined

“The pollen monitor is able to update measurements on an hourly basis,” said Sulz. “A dense network of such devices in Germany would considerably improve the current situation, making our forecast models more precise.” The pollen monitor is not in use yet, but the German Weather Service is planning to set up 15 to 30 such systems before 2010. The individual components of the system are also of interest for other applications. For example, they could be adapted to analyse the air in operation theatres and to detect bacteria. They could also be used to detect agricultural pests, for example the spores of crop fungi.

mn – 14th May 2008
© BIOPRO Baden-Württemberg GmbH
Further information:
Gerd Sulz
Head of Project
Fraunhofer Institute for Physical Measurement Techniques IPM
Heidenhofstraße 8
79110 Freiburg
Tel.: +49 (0)761/8857-293
E-mail: gerd.sulz@ipm.fraunhofer.de
Website address: https://www.gesundheitsindustrie-bw.de/en/article/news/a-pollen-monitor