Tear Fluid as a Matrix for Biomonitoring Environmental and Chemical Exposures

Abstract

Purpose: Exposures to hazardous chemicals have been linked to many detrimental health effects. It is critical to have effective biomonitoring methods to measure the levels of these chemicals in humans to better evaluate key environmental exposures that increase the risk of chronic disease and death. Traditional biomonitoring utilizing blood and urine is limited due to the specialized skills and invasiveness of collecting these fluid samples. The systematic review focuses on the tear fluid, which is largely under-researched, as promising alternative to these traditional fluids. The objective is to evaluate the practicability of using human tear fluid for biomonitoring environmental exposures, highlighting potential pitfalls and opportunities. Recent finding: Tear fluid biomonitoring represents a promising method for assessing exposures. Tear fluid uniquely interfaces with the external environment at the air-tear interface, providing a surface for airborne chemicals to diffuse into the ocular environment and interact with biomolecules. Tear fluid also contains molecules from the internal environment that have travelled from the blood to tears by crossing the blood-tear barrier. Our review shows that tear fluid can be used to identify hazardous chemicals from the external and environment environments and to differentiate between different exposure groups. Summary: The review provides a critical analysis of the current state of knowledge in tear-based biomonitoring and draws attention to the promise of using the method for noninvasively increasing access to exposure assessment. The method will become acceptable for routine use as more individual and inter lab studies focus on broadly identifying and quantify exposure markers in tears, understanding factors that influence reliability of the method and standardizing the tear fluid method.