Eye irritation is one of the most frequently reported symptoms in relation to working in office-like environments. So far, no consistent association has been found between concentration of airborne particles and prevalence of eye irritation. External physical factors not hitherto considered could have a large influence on particle deposition velocity onto the ocular surface. This may have obscured the role airborne particles play. Based on previously published semi-empirical models, the paper describes the influence of turbulence, gravitational settling, electrical fields, and thermophoresis on deposition velocity. A probabilistic approach was used to determine percentile ranges in deposition velocity when the magnitude of these parameters varied within typical ranges. The calculations suggest that differences in external factors other than particle size may cause differences in the deposition velocity of one order of magnitude or more. Studies trying to find associations between airborne particle concentration levels and eye irritation should take into consideration the influence of external physical factors on deposition velocity.
Practical implications: External physical factors other than concentration are likely to have a large influence on the deposition rate of airborne particles onto the ocular surface. Thus, future studies on associations between airborne particle levels and eye symptoms should only be conducted if particle concentration measurements are suitably size resolved. Other relevant external physical factors should also be assessed and included in a multivariate analysis of exposure-response associations.