Incorporation of Fast-Elimination Chemicals in Hair Is Governed by Pharmacokinetics–Implications for Exposure Assessment

Abstract

Mechanisms governing chemicals’ incorporation in hair are incompletely understood, and gaps remain to link the concentration of chemicals in hair to level of exposure and internal dose present in the body. This study assesses the relevance of hair analysis for the biomonitoring of exposure to fast-elimination compounds and investigates the role of pharmacokinetics (PK) in their incorporation in hair. Rats were administered with pesticides, bisphenols, phthalates, and DINCH over 2 months. Hairs were analyzed for 28 chemicals/metabolites to investigate correlations between their concentration in hair and the dose administered to the animals. Urine collected over 24 h after gavage was used to determine chemicals’ PK and to investigate their influence on incorporation into hair by means of linear mixed models (LMMs). Eighteen chemicals presented a significant correlation between concentration in hair and level of exposure. In models combining all chemicals, agreement between concentration in hair predicted by LMM and experimental values was moderate (R 2 = 0.19) but significantly increased when PK were included in the models (R 2 = 0.37), and even more when chemical families were considered separately (e.g., R 2 = 0.98 for pesticides). This study shows that pharmacokinetics mediate incorporation of chemicals in hair and suggests the relevance of hair for assessing exposure to fast-elimination chemicals.

The Effects of Environmental Pollutants and Exposures on Hair Follicle Pathophysiology

“…In many biomonitoring studies, pesticide exposure has been accurately tracked through hair concentrations [109][110][111][112][113][114][115][116][117][118][119][120]. The ability to track pesticide residue in hair shafts indicates that pesticides may have significant accumulation in the HF.…”