B.4.1. Exposure linkage assessed
This section discusses the approach used, including the models, to assess the risks to people operating commercial equipment during the mixing and application of pesticides. How personal protective equipment (PPE) reduces these risks if used correctly is also be considered.
B.4.2. Model used
The UK Chemicals Regulation Directorate (UK CRD) version of the German Federal Biological Institute’s (BBA) operator assessment model is used. The UK CRD exposure model calculates exposure using the results of actual measurements carried out in the field (Chemicals Regulation Directorate, 2016a).
This is considered a suitable model for operator exposure because it:
is an internationally developed model based on a robust dataset
estimates the total internal dose of a pesticide for the operator from dermal and inhalation exposures
is most appropriate when assessment exposure and risk using the Acceptable Operator Exposure Limit (AOEL), where comparison with an internal dose is appropriate
allows the estimates to be modified to take account of use of personal protective equipment, gloves, overalls, goggles and respirators in a relatively flexible way
allows the risk assessor to apply New Zealand specific values for application rates, application methods (air blast/boom/backpack sprayer), work rates per day and hectares per day treated.
B.4.3. Assumptions and uncertainties
The UK CRD version of the BBA operator exposure model calculates exposure using the results of actual measurements carried out in the field (Chemicals Regulation Directorate, 2016a). These values represent the geometric mean values of these studies and so may not be as conservative as some other operator exposure models which are based on the 75th percentile of exposure datasets. However, this approach is considered more realistic for long-term work patterns and the EPA is satisfied that this is an acceptable approach.
Pesticide application technology is improving and engineering controls evolve. The assumptions in this model are for older equipment and, are hence, conservative.
B.4.4. New Zealand specific parameters
The risks to an adult worker during a standard working day, as set out in Table B.2, are typically assessed.
No other parameters have been amended to be specific to New Zealand.
Table B.2 Worker default values
Parameter Value
Body weight 70 kg
Working day 8 hours
B.4.5. Default values
The work rate, or area to be treated per day, should be based on that proposed by the applicant, or from user feedback for reassessments. If this information is not available then the default values in the EFSA exposure assessment model are used, see Table B.3. These values are consistent with feedback received during the organophosphate and carbamates reassessment. For handheld applications, one hectare is considered to be treated per day.
Table B.3 Work rate
Crop Area treated per day (ha)
Bare soil 50
Berries and other small fruits (low) 50
Brassica vegetables 50
Bulb vegetables 50
Cane fruit 10
Cereals 50
Citrus fruit 10
Fruiting vegetables 50
Golf course turf or other sports lawns 50
Grassland and lawns 50
Grapes 10
Hops 10
Leaf vegetables and fresh herbs 50
Legume vegetables 50
Oil fruits (high crops) 10
Oilseeds 50
Ornamentals 10
Pome fruit 10
Root and tuber vegetables 50
Stone fruit 10
Tree nuts 10
From EFSA 2014
The impact of wearing different forms of PPE is estimated using exposure reduction factors which have been empirically derived. These protection factors are based on the 2014 EFSA exposure model (EFSA, 2014) and are outlined below in Table B.4.
Table B.4 PPE exposure reduction factors PPE
Exposure reduction coefficients
Dermal Component Inhalation
Gloves (liquid) 0.1 Hands NA
Certified protective coverall
0.05 Body NA
Hood and visor 0.05 Head NA
FP1, P1 and similar respirators
0.8 Head 0.25
FP2, P2 and similar respirators
0.8 Head 0.1
Gloves (solids mixing and loading)
0.05 NA NA
B.4.6. Model outputs
The UK CRD model produces predicted exposure concentrations. Exposure values are derived for several scenarios with different levels of PPE:
No PPE during mixing, loading and application
Gloves only during mixing and loading
Gloves only during application
Full PPE during mixing, loading and application (excluding respirator)
Full PPE during mixing, loading and application (including FP1, P1 and similar respirator achieving 75% inhalation exposure reduction)
Full PPE during mixing, loading and application (including FP2, P2 and similar respirator achieving 90% inhalation exposure reduction.
B.4.7. Risk
The level of PPE that is required is determined based on which scenario reduces exposure, compared to the AOEL, so that the risk quotient (RQ) is below one and therefore at an acceptable level:
𝑅𝑄 = 𝐸𝑥𝑝𝑜𝑠𝑢𝑟𝑒 𝐴𝑂𝐸𝐿
Equation B.1 If the RQ is greater than one, then other options may be considered in conjunction with the conceptual model; for example, measurements of relevant real-life exposures to refine the understanding (such as OECD, 1997).
B.4.8. Alternative options considered
The UK CRD variation of the BBA exposure model is used in New Zealand to take advantage of the model and documents’ translation into English.
A number of parameter values from the 2014 EFSA operator, worker, resident and bystander exposure model (EFSA, 2014) are used as they are more recently available. This model is not currently used because of concerns over the applicability of the assessment of bystanders from aerial applications to the use patterns in New Zealand.
The UK POEM model (described further in section B.8) can also be used to assess the risks to commercial operators. However, as it has fewer options for operator PPE the EPA has decided not to use it when conducting the risk assessment.