Væksthusarbejderes eksponering over for det mikrobiologiske bekæmpelsesmiddel Veryicillium lecanii som funktion af arbejdsprocesser

Exposure of Greenhouse Workers to the Microbiological Pest Control Agent Verticillium lecanii as a Function of Specific Working Processes

Summary and conclusions

The objective of the project was to investigate the exposure of glasshouse workers to the microbiological pest control agent Verticillium lecanii as a function of specific working processes in pot plant production and of the application technique used. Further, it was investigated whether the microbiological control agent was spread to other parts of the glasshouse nursery than in the house where the agent was applied, and whether V. lecanii propagates on the pot plants after application.

Six trials comprising three glasshouse nurseries and four pot plant cultures were included. In all trials V. lecanii was applied with the local equipment, and the local formulations were used. Furthermore, registrations were carried out during the local working processes. No attempts were made to standardise the procedures.
Registrations were made during working processes right from the application and to the final packing of the ready for sale product. Registrations comprise colony forming units (CFU) of V. lecanii from leaves and the pot soil surface, CFU washed off hands, arms and face, CFU washed off small pieces of cloth fastened to different parts of the body, besides CFU in the air, collected by means of a Satorius MD8 air sampler. Registration of the presence of V. lecanii on leaves and soil surface of the pot plants was made in order to be able to follow the potential source of exposure during the various steps of the production. Registrations of deposition of spores on skin and cloth and presence in the air were made to quantify the possible exposure of glasshouse workers to spores of V. lecanii.

Values of spore deposit on skin varied between 0 and 10⁵ CFU per 100 ml water used for washing. The frequency and quantity of contamination of hands were much higher than for arms and face. The two working processes: “Dipping of stem cuttings in a suspension of V. lecanii spores followed by planting” and “ Removal of plastic cover from a table with plants” gave the highest contamination of hands. The CFU values from cloth were much lower, ranging between 0 and 85 CFU per 100 ml washing water.

The concentrations of spores in the air varied very much between the individual working processes. The highest values of CFU per m³ air were recorded during the working process: ”Removal of plastic cover from a table with plants”. Values from three trials reached 23,3000, 26,400 and 180,000 CFU/m³, which is above the level of 5 x10⁴ proposed by Gorny & Dutkiewicz (2002) for occupational limit for industrial installations, and above the concentration causing eye and nose irritation according to Anonymous (2002).

The results of the registration of spores of V. lecanii on leaves and soil surface during the production cycle showed varying values, but values above 10⁵ CFU per leaf or 3.8 mm²soil surface were not unusual. Very high CFU values recorded during the last working procedure: “Packing the plants” show that maintenance and in some periods also propagation of V. lecaniitakes place during the production cycle. The varying values show that fluctuations in population density occur.

It is concluded that spores of V. lecanii are released to the air during working processes after application, and that the microbiological control agent is spread to other compartments of the nursery than where the agents are applied.

It is, further, concluded that glasshouse workers are exposed dermally, especially via their hands, and respiratory during some working processes where high concentrations of spores are released to the air. On the other hand, no essential influence of the application method: dipping, hydraulic spraying or mist spraying, was registered on the matters discussed above. However, dipping caused the highest hand contamination.