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Table 6 Literature reported engineering and production parameters affecting personal exposures of farmers to bio-aerosols

From: Respiratory diseases and allergy in farmers working with livestock: a EAACI position paper

Determinant Substance Factor Estimated effect Source
 Environment Dust, endotoxin Season, summer Lower levels of exposure compared to winter [43, 124, 126, 129]
Dust, endotoxin Outdoor temperature 18–36% decrease in levels per 10 °C increase in temperature [43, 124]
 Production stage Dust Finishing units Exposures highest in finishing and/or weaning stables and lowest in farrowing and/or breading. [166, 167]
 Ventilation Dust Negative pressure lower exposures compared with neutral or mixed methods by 26–50% [43]
Dust, endotoxin Air exhaust via other compartments or the pit Increased exposures relative to when characteristic not present by 28–42% [124]
Endotoxin Use of a showering system 7% increase of exposure per 10 min spent on presence of characteristic [43]
 Feeding Dust Automatic feeding Lower exposures with increased time spent on presence [124]
Dust, endotoxin Wet feed Lower levels when compared with dry feed by 21–79% [43, 124]
Dust Fat in feed Increased fat content associated with lower levels of exposure [132]
Dust Ad libitum feeding 5% increase in levels per 10 min spent on presence of the characteristic [43]
 Flooring Endotoxin Full slatted floor Full slatted floor associated with increased exposure levels by 50% compared with a full concrete or 16% for every 10 min spent on presence [43, 124]
Dust Fully concrete floor Fully concrete floor associated with 21% decrease in dust exposure [124]
Endotoxin floor heating 38% increase in exposures per 10 min spent on presence [124]
 General hygiene Dust, endotoxin Very dusty stable 7–18% increased exposure compared to a non-dusty environment [124]
Dust Wet floor Reduced levels compared to dry floor by 12% [168]
 Other Dust Ventilation and floor, and manure type combinations Exposures lowest in natural ventilated buildings with slatted floors. Highest exposures in mechanically ventilated buildings with scrapper manure collection. [169]
 Environment Endotoxin Outdoor temperature ≥ 18% decrease in levels per 10oC increase in temperature [111, 119, 128]
 Feeding Endotoxin Semi-automatic system 42% reduction compared to manual feeding [111]
Dust Amount of feed (pellet, meal) 2% increase in exposure per kg distributed [111]
 Bedding Dust, endotoxin, glucans Compost bedding Compost bedding associated with higher exposures compared to rubber mats by 5% for dust and 179 to 400% for the constituents [114, 135]
 Animal density Dust, endotoxin, bovine allergens Surface area per cow Increased surface associated with decreased levels of exposure by 7 to 65% [114, 115, 135]
 Manure handling Dust Automatic scrapers in alley ways 40% reduction compared to when system not used [128]
Endotoxin Slope or back flashed system in pit 175% increase compared to round or scraper based systems [128]
 Milking Dust, glucans, bovine allergens Robot Robots associated to increased exposure compared to parlour milking by 22–86% for dust and 138% for glucans but decreased exposures to bovine allergens by 65%. [114, 128, 135]
 General hygiene Dust, endotoxin Parlour cleaning Increased frequency of parlor cleaning associated with lower levels of dust and endotoxin [170]
 Environment Dust, endotoxin Season, summer Somewhat lower levels of exposure compared to winter for layers, and turkey farmers [133, 134]
 Barn system Dust, endotoxin Floor (aviary) Floor (Aviary) housing system results in higher concentrations relatively to cage housing [165, 171, 172]
Dust Enclosed system Higher exposures in systems that are enclosed (only mechanical ventilated) compared to those being open with both mechanical and natural ventilation present [134]
 Production stage Dust, endotoxin Flock age Increased flock age associated with decreased exposures [129, 134, 164]
Dust, endotoxin Parent stock Levels in parent stock farm higher compared to broiler and layers [134]
Dust, endotoxin Hen (Turkey) Levels in hen stables higher compared to those of toms and brooders [133]
 Ventilation Dust, endotoxin Ventilation rate Increased ventilation rate related to decreased levels of exposure [133]
 General hygiene Dust, endotoxin Litter presence in control alleys Presence of litter in control alleys assoc. with higher exposures compared to no presence [134]
 Other Dust, endotoxin Tilling of litter Performance of litter tilling related with increased levels of exposure [133]