Possible Associations Between Changes of the Precorneal Eye Tear Film, Eye Complaints, and Reactive Chemistry Indoors

November 3, 2003 - 12:00pm
Bldg. 90
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Eye complaints are among the most common symptoms reported in office environments. The pathological mechanisms causing eye complaints depend to some extent on the precorneal tear film (PTF) stability. Dryness of the PTF leads to eye complaints. Dryness of the PTF occurs by (i) low relative humidity, (ii) decreased blinking & widened ocular surface area due to increased task attention, and (iii) individual characteristics (tear film alterations, blinking disorders, contact lense use). These factors are responsible for progressively increased water evaporation from and thinning of the PTF, causing an increase of dryness, the formation of dry spots on the cornea, and possibly epithelial alteration of cornea and conjunctiva.    Certain organic chemical compounds in indoor air (OCIAs) (e.g. acrolein and formaldehyde) and products of ozone reactions with terpenes represent another possible cause of eye complaints (mediated through trigeminal stimulation) that may be exacerbated by low relative humidity.  Some OCIAs are chemically reactive (e.g.., with ozone and the hydroxyl radical). Common OCIAs include terpenes, emitted from wood, plant, and fruit based products (e.g. citrus and pine oils), and commonly used as fragrances in household products. Ozone oxidizes most terpenes under typical indoor conditions, producing a number of acids, diacids, aldehydes, ketones, and mixed aldehyde-keto-carboxylic acids. Based on a mouse bioassay and a human eye exposure model, it is inferred that oxidized terpenes produce irritants that cannot be identified by conventional sampling techniques. Change in blink frequencies appears to be a promising measure of trigeminal stimulation from exposure of the eye to gaseous irritants in near realistic concentrations.

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