Table 13.
Data derived using the BREAM calculator and the scenario specified
| BREAM calculator input | Value | Notes |
|---|---|---|
| Nozzle type | FF03110 | Conventional flat fan nozzle. It is the only data set currently available. From other drift data, it is clearly not the worst‐case nor the best case |
| Number of nozzles | 48 | Represents single pass of a 24‐m boom. Further upwind passes could possibly contribute additional drift, but the wind conditions will not be identical and the additional contribution from including more upwind nozzles or passes is relatively small |
| Boom height | 0.7 m | The optimum height is 0.5 m, but anecdotal evidence suggests modern practice involving large sprayers travelling at fast forward speeds exceeds this. Spray drift increases with boom height |
| Forward speed | 12.6 km/h | Considered to be the upper end of the current ‘average’ in the UK based on expert opinion (i.e. 3.5 m/s, hence 12.6 km/h). A 2004 UK survey showed that between 15% and 20% of the area treated by large or self‐propelled sprayers was done using average speeds in the range 13–16 km/h |
| Spray concentration | 1 g a.s./L spray | Used to generate unit values which can be adjusted by product‐specific values |
| Crop height | Short | The model does not yet support estimation of exposure from spraying other crops |
| Wind speed | 2.7 m/s | Upper limit of what is considered acceptable for spraying in the UK Code of Practice |
| Bystander type | Child and adult | Data collected on adult and child mannequins. Adult were 1.87 m tall. Child mannequins were 1.03 m tall (i.e. about median height for a 4‐year‐old child) |
| Exposure route | Dermal and inhalation | Taking into account the surface areas of body parts (Table 7) and the updated values for breathing rates (Tables 4 and 5) |
| Dermal absorption | 100% | Used to give an estimate of the external dose, which later can be adjusted by appropriate dermal absorption values |
| Inhalation rate | Bystanders | Inhalation reflective of high‐intensity activity |
| Children 2.28 m3/h | The body weight assumed in this guidance is 10 kg, which is representative of children around 1 year old. Therefore, to be compatible with this body weight, an average high activity breathing rate of 0.228 m3/h/kg bw should be used, and the rate per hour becomes 0.228 m3/h/kg bw × 10 kg = 2.28 m3/h | |
| Adults 3.18 m3/h | i.e. 0.053 m3/h per kg bw × 60 kg | |
| Residents | Daily average inhalation rate | |
| Children 0.33 m3/h | The body weight assumed in the guidance is 10 kg, which is representative of children around 1 year old. Therefore, to be compatible with this body weight, an average breathing rate of 0.80 m3/day/kg bw should be used, and the rate per hour becomes 0.80 m3/day per kg bw × 10 kg bw/24 h = 0.33 m3/h | |
| Adults 0.675 m3/h | i.e. 0.27 m3/kg bw per day × 60 kg bw/24 h | |
| Distance from source | 2 m | Considered to represent a realistic worst‐case distance. For example, this could represent a sprayer operating at the edge of a field with a resident/bystander in a garden separated from the field by a simple wire fence and with both the spray operator and resident/bystander unaware of each other’s actions |
Note: A typical F11003 nozzle operating at 3 bar, at the above forward speed would apply about 120 L/ha which is 12 mL/m2 and at the spray concentration of 1 g/L. Assuming above, this would deliver 120 g/ha or 12 mg/m2. The model is a good predictor for short crop and short vegetation.