Application of nail analysis in human biomonitoring of toxic pollutants: A review.

Nail tissue, as a keratinized biomatrix, serves as a valuable indicator of chronic human exposure to toxic pollutants. The analysis of nail samples has emerged as a prominent method for human exposure assessment, primarily due to its non-invasive sampling procedure and ease of sample storage and transportation. This review examines recent applications of nail analysis in human biomonitoring of toxic organic compounds and heavy metals, along with the various pretreatment methods that have been developed. Studies of human nail samples have revealed distinctive patterns in toxic pollutant accumulation. Brominated flame retardants exhibit significant occupational exposure differences, with concentrations reaching 2.20 × 106 ng/g in manufacturing workers compared to 67 ng/g in the general population. Organophosphate esters demonstrate notable regional variations, as evidenced by Triphenyl phosphate concentrations of 19.6 ng/g in China versus 770 ng/g in the United States. Additionally, the detection of organic pollutant metabolites in nails provides direct evidence of internal exposure. The 5-14 months detection window characteristic of nail samples enables retrospective exposure analysis, highlighting the promising potential of nail analysis in human biomonitoring. Recent developments include the implementation of in situ analytical methods for rapid heavy metal detection in nail samples. However, a significant challenge remains in differentiating between internal and external sources of most compounds in nails, although the identification of metabolic biomarkers for certain pollutants can minimize external interference and better reflect actual body burden. Further research is required to elucidate the relationships between nail pollutant levels, environmental exposure, and health effects. While existing studies demonstrate the considerable potential of nail analysis in human biomonitoring of toxic pollutants, additional research is necessary to validate and fully realize its practical applications.