Intervention scenario | Description of parameter change | Change in model input parameters | ||

Flour dust exposure | Fungal α-amylase | Population parameters^{*} | ||

No intervention | – | GM=1.19 GSD _{bw}=2.29GSD _{ww}=2.27 | GM=0.57 GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0.3 |

Covenant intervention | ▸For first 6 years, population GM exposure decreases by 2% annually for flour dust and 8% annually for fungal α-amylase ▸After the 6-year level, exposures stay constant ▸Variability is assumed to stay the same | Year t=1–6; GM=GM(t−1)×0.98Year t=7–20; GM=1.05GSD _{bw}=2.29GSD _{ww}=2.27 | Year t=1–6; GM=GM(t−1)×0.92Year t=7–20; GM=0.35GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0.3 |

Continuation of covenant | ▸Equal to the above described scenario ▸However, the decrease in the GM values for both exposures is continued for the full 20-year period | GM=GM(t−1)×0.98 GSD _{bw}=2.29GSD _{ww}=2.27 | GM=GM(t−1)×0.92 GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0.3 |

Hygiene intervention | ▸Individual exposure estimates from the baseline measurement dataset are recalculated according to the reduction factors derived previously | GM=0.82 GSD _{bw}=2.03GSD _{ww}=2.05 | GM=0.39 GSD _{bw}=2.56GSD _{ww}=4.44 | Prob_atopy=0.3 |

Health surveillance intervention (I) | αExposures of high risk individuals (sensitised workers) are reduced by 90% ▸Individual workers can only receive an intervention once ▸The population variability of exposure is assumed to remain unchanged | High risk individuals:GM _{post-int}=0.1×GM_{pre-int}Others:GM _{post-int}=GM_{pre-int}GSD _{bw}=2.29GSD _{ww}=2.27 | High risk individuals:GM _{post-int}=0.1×GM_{pre-int}Others:GM _{post-int}=GM_{pre-int}GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0.3 |

Health surveillance intervention (II) | ▸As above, but now non-sensitised workers with rhinitis symptoms are also included in the definition of high risk workers | High risk individuals:GM _{post-int}=0.1×GM_{pre-int}Others:GM _{post-int}=GM_{pre-int}GSD _{bw}=2.29GSD _{ww}=2.27 | High risk individuals:GM _{post-int}=0.1×GM_{pre-int}Others:GM _{post-int}=GM_{pre-int}GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0.3 |

Pre-employment screening | ▸Exposure parameters are not affected ▸The probability of atopy for new employees is set to 0 assuming no atopic subjects enter the workforce | GM=1.19 GSD _{bw}=2.29GSD _{ww}=2.27 | GM=0.57 GSD _{bw}=2.77GSD _{ww}=4.57 | Prob_atopy=0 |

↵* Only the probability of being atopic (Prob_atopy) is relevant for the evaluated intervention strategies.

GM, geometric mean exposure level; GM

_{pre-int}, individual exposure estimate before receiving an individual intervention; GM_{post-int}, individual exposure estimate after receiving an individual intervention; GSD_{bw}, the between worker or inter-individual exposure variability; GSD_{ww}, the day-to-day or intra-individual exposure variability.