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Health effects of predatory beneficial mites and wasps in greenhouses

4 Exposure assessment

• 4.1 Sources of information
  • 4.1.1 Inquiry in 1996
  • 4.1.2 Information from questionnaires 1997-2001
  • 4.1.3 Horticulture inquiry 2004
• 4.2 Individual exposure assessment

The purpose with this part of the project has been to get estimates of the person and time specific exposure to each of the relevant beneficial animals.

Due to lack of direct measurements of exposure to airborne antigens from the predatory animals and the non-beneficial mites, this exposure assessment has to be based on information about the use in the relevant time period 1997-2001.

4.1 Sources of information

There have been three sources to this information:

1. Data from the initial inquiry in 1996 before the start of the study.
2. Questionnaire reports from the workers at the annual examinations.
3. An inquiry conducted in 2004 at the participating greenhouse firms.

4.1.1 Inquiry in 1996

As part of the planning of the BIOGART study in 1996 a survey was carried out among the 205 registered greenhouse enterprises that had employees. The greenhouses were selected from the employers’ organization and the owners of the enterprises were mailed a questionnaire followed by a telephone interview.

The interview mainly concerned microbiological pesticides, but there was a final, open question about beneficial species.

Interviews were obtained from 193 (94 %) responders and among these the actual group of participating greenhouses was chosen.

4.1.2 Information from questionnaires 1997-2001

The annual examinations included a questionnaire on the working conditions including handling of beneficial species.

The questionnaire comprised a section about present and former employments, skills (skilled or unskilled worker), time of employment at the actual greenhouse and in the trade as a whole.

Sections about working function, cultures, handling of microbiological pesticides, beneficial species as well as chemical pesticides during the past year, were included.

The work tasks carried out in the previous year were scored by ranking a preset series of working procedures according to the part of the working time spent (most of the time, ¾ of the working time, ½ of the time, ¼ of the time or more rare).

The time spent at each of the different cultures was scored in the same way.

Regarding beneficial species only the persons own handling of the products were registered. It was possible to register up to seven different beneficial species and for each of these the type, mode and frequency of application, the treated culture, the area applied and the use of personal protection.

Similar groups of questions were made for the microbiological and the chemical pesticides.

4.1.3 Horticulture inquiry 2004

In 2004 an inquiry was conducted with reference to the use of beneficial species in greenhouse firms in Funen in the period of 1997-2001.

The purpose of this part of the investigation was to verify the workers reports about the use of beneficial species in the greenhouse firms and hereby helping to assess the extent of exposure, both directly when applying the species and indirectly by handling the plants.

4.1.3.1 Method

The study group consisted of employees at the 31 greenhouse firms in Funen who participated in the BIOGART study.

Data collection was conducted by telephone interviews between the 8^th and the 28^th of June 2004. All the greenhouse firms received 1-2 weeks prior to the interview, written information about the investigation and an outline with a table of the information we would like to obtain. Receiving the form before hand gave the greenhouse firms the possibility of finding the information that would be 3-7 years old at the time of contact.

Some of the greenhouse firms were in the meanwhile closed down and others had changed ownership. If possible, the previous owner or contact person was contacted and interviewed. Contact attempts were made up to four times and were successful with 30 out of 32 greenhouse firms (93 %).

The interviews lasted from a few to 45 minutes and were based on the form received. The interviews were focused on the use of six selected beneficial species and one pest species in the greenhouse firms in the period of 1997-2001. For each of the species was asked: when it was used, how and in which cultures it was released, what was the size of the treated area, what about the frequency and the amount at each release, and who the supplier was.

Data were keyed in using Epidata, version 3.02, and analyzed in the statistical package STATA, version 8.2.

4.1.3.2 Results

Valuable information was obtained from 15 of the 31 greenhouse firms. These 15 firms had employed 404 of 579 or 70 % of the participants in the follow up. Eleven of the firms had been using beneficial species in the period whereas four had not.

The sixteengreenhouse firms did not participate, due to various reasons (lack of time or lack of interest, change of ownership since last approach three years ago, approaching close down, two firms stated that they were fed up with inquiries and others simply could not or did not have the capacity to find data from the time period).

4.2 Individual exposure assessment

As the first step in the assessment of the individual exposure, each person in each run was assigned a level of exposure to each of the six beneficial species.

If the person had reported use of the species in the questionnaire in a run, exposure was assigned “Applying” in the specific period.

If at least one person in a greenhouse in a run had reported “Applying”, it was compared with the results of the 2004 inquiry. If there was agreement, the exposure was assigned “Exposed in the greenhouse” for the rest of the participants in the greenhouse in the particular run and the level of confidence was set to “high”.

If there was no agreement between the information from the greenhouses and the questionnaires from the employees (mostly if one of the persons had registered ”Applying” and the greenhouse had stated that it was not used in the particular year), an individual evaluation was made, based on the data in the questionnaire and the use the year before or after. The level of confidence of the greenhouse was then assigned to “low”.

For the greenhouses where information only was available from the questionnaires the level of confidence was set to “intermediary”.

The distribution of the exposure assignments for the three levels of confidence is shown in table 4-1.

In the analyses of the effects of exposure on the different effect measurements, separate analyses were made of the whole material and for the subgroup, with high level of confidence which amounted to about 75 % of the observations.

Figure 4.1. The distribution of exposure to the four different predators. The bars in each group show the frequency in run 0 through run 3.

Table 4-1. Exposure of the individuals in run 2 and run 3 to the different beneficials. Based on the level of confidence of the information from the annual questionnaires from 1997 to 2001 and the inquiry to the greenhouse owners in 2005.

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Version 1.0 August 2007, © Danish Environmental Protection Agency