Hair specimens in exposome-health research: Opportunities, challenges, and applications

The integration of hair samples into human biomonitoring methods marks a significant shift in exposome-health research. The exposome concept covers all exposures throughout a person's life. This paper discusses the use of hair as a non-invasive biomarker that records long-term exposures, contributing significantly to the exposome framework. Hair is unique in its ability to accumulate both hydrophobic and hydrophilic substances, thus serving as an essential tool for capturing a diverse array of lifetime exposures, from metals to organic pollutants. Recent research highlights the potential of hair as a biomarker, but also points out analytical challenges, particularly due to its complex composition and the lower concentrations of external chemicals present. The paper emphasizes the considerable potential of hair samples in exposome-health research. They are used to measure exposure to various environmental pollutants (organic chemicals and elements), societal behaviors, and lifestyle factors, and can also reflect the body's response. The article highlights advancements in analytical techniques, especially mass spectrometry and untargeted strategy, which have enhanced our ability to detect a wide range of environmental pollutants in hair, from environmental emissions to household chemicals. However, the study also acknowledges the difficulties in analyzing hair. One major challenge is comprehending the ‘entire chemical composition’ within hair, which is complex due to its intricate matrix. The extraction and purification processes are challenging, requiring sophisticated methods for precise substance extraction. The paper anticipates future research to more clearly establish the connections between hair sample data and health outcomes. The potential of hair samples in exposome-health research is enormous, but to realize this potential, we must overcome analytical challenges and deepen our understanding of how hair content relates to health. The document advocates for a unified effort to develop standardized methods, enhance analytical sensitivity, and set reference ranges for chemical concentrations in hair, thus improving its reliability as a biomarker in environmental health research.