Exposure estimation for plant protection products
Exposure estimation: consumers
Monitoring authorities, quality control laboratories, advisory services and risk management often find it difficult to assess whether a plant protection product residue in a food sample poses an acute or a chronic risk for the consumer. The main reason for this is that often they have limited access to the necessary information, as some of it is only available to the authorities involved in the authorisation and assessment of plant protection products.
For this reason, the BfR has prepared various assessment aids to support experts in their evaluation whether the residue of a plant protection product in a food sample poses a risk to consumers or not.
For the risk assessment of residues of plant protection products BfR has developed a model for estimating long and short-term intake of residues. It supplements the "VELS Model", which was published back in 2005 and which is based on representative consumption data of German children aged 2 to under 5 years. In addition, comprehensive representative information on the consumption behaviour of the German population aged 14 to 80 years is available from the National Nutrition Survey II (NVS II), which was conducted in 2006. This consumption data is more up-to-date than the VELS data and also takes into account consumption of foods rarely eaten by children. Using the "NVS II Model", risk assessments can be made for children and adults based on consumption data from Germany. Moreover, EFSA provides the "PRIMO" model (Pesticide Residue Intake Model) for calculation of the acute and chronic risk of plant protection product residues based on European consumption data (see external links).
Information on consumption models and related topics can be found here:
- https://www.bfr.bund.de/cm/343/bfr-berechnungsmodell-zur-aufnahme-von-pflanzenschutzmittel-rueckstaenden-nvs2.zip (PDF file,654.17 KB)
- https://www.bfr.bund.de/cm/343/neues-bfr-modell-fuer-die-deutsche-bevoelkerung-im-alter-von-14-bis-80-jahren-nvs-2.pdf (PDF file,37.51 KB)
For residue analysisof a plant protection product active substance in food items, mixed samples from several units are normally examined rather than individual units. This provides an overall more representative view on the residue situation. In case an even, uniform mixture of individual units of a food prior to consumption cannot be assumed (e.g. corn), the assessment must always take into account that consumers eat one, single, highly contaminated unit of a food.
To ensure that mixed samples do not lead to an underestimation of a possible acute risk, the residue in the mixed sample is multiplied by a variability factor. It is standard here to use variability factors of 5 or 7 (depending on the weight of one unit). These are pre-set in the consumption models. A number of specific variability factors were also derived on the basis of empirical data from residue studies with plant protection products in which individual units were examined instead of mixed samples (“variability studies”). In most cases, the specific factors lie between 2 and 3 and substitute the standard variability factor for each active substance/food combination. The BfR provides information on these specific variability factors.
More information on variability factors (in german):
von_verbrauchern_gegenueber_pflanzenschutzmittelrueckstaenden.pdf (PDF file,131.87 KB)
Agricultural products are often not eaten raw, but are processed prior to consumption. Processing may change the residue level of the active substances of plant protection product contained in the agricultural product. The ratio of the residues in the processed product to the corresponding unprocessed product is called the processing factor. It indicates whether residues are accumulated or reduced during processing. Processing factors are determined in laboratory experiments simulating food processing conditions. Details of such studies, which have to be presented by plant protection product manufacturers in the course of authorisation procedures, are not publicly available.
For this reason, the BfR has been offering a periodically updated compilation of processing factors since 2007.
The BfR has also prepared flow chart illustrations of typical processes. In this way, the database allows a quick overview of the relevant products and intermediate products of food processing, and processed matrices can be assigned more easily.
Information about data collection and relatedtopics can be found here:
- https://www.bfr.bund.de/cm/349/bfr-data-collection-on-processing-factors.pdf (PDF file,74.43 KB)
- https://www.bfr.bund.de/cm/349/bfr-compilation-of-processing-factors.xlsx (PDF file,685.40 KB)
- https://www.bfr.bund.de/cm/349/bfr-compilation-of-processing-factors-flow-charts.pdf (PDF file,36.56 MB)
Exposure estimation: Users, workers, local residents and bystanders
The BfR performs its exposure estimation by applying models initially based on very conservative assumptions. The exposure of users of plant protection products (mostly farmers, but also horticultural workers and non-professional users in private households and small gardens) is determined on the basis of the so-called “German model” (Lundehn et al., 1992). The model used to determine the exposure of workers during follow-up work was published by Krebs et al. (2000). In the exposure estimation for professional users, it can be taken into account that, under certain circumstances, contact with plant protection products is reduced, e.g. due to special protective clothing. Other measures, such as the use of ready-to-use plant protection products, bait boxes, childproof caps and water-soluble bags, are also suitable for protecting non-professional users and the general public.
Guidelines for calculating the exposure of bystanders and local residents were published by Martin et al. (2008). Children in particular were taken into consideration, as their behaviour differs greatly from that of adults, especially in their first few years of life. Small children often put their fingers in their mouths and may even swallow objects such as sand and plant parts. If it cannot be excluded that the application of a preparation poses a potential risk to uninvolved persons based on this estimation, appropriate measures are required, such as the use of special drift-reducing equipment.
Information about the calculation models and related topics can be found here:
- https://www.bfr.bund.de/cm/343/anwendersicherheit_deutsches_modell_v1.xls (PDF file,77.00 KB)
- https://www.bfr.bund.de/cm/343/schutz_von_personen_bei_nachfolgearbeiten_v1.xls (PDF file,36.00 KB)
- https://www.bfr.bund.de/cm/343/schutz_von_nebenstehenden_und_anwohnern_v1.xls (PDF file,170.50 KB)
- https://www.bfr.bund.de/cm/343/safeguarding_the_health_of_operators_german_model_introduction.pdf (PDF file,24.02 KB)
- https://www.bfr.bund.de/cm/343/safeguarding_the_health_of_workers_re_entry_exposure_introduction.pdf (PDF file,15.02 KB)
introduction.pdf (PDF file,21.61 KB)