Chlorinated paraffins in plasma of healthy elderly adults: Method development, temporal variability, and exposure determinants.

Chlorinated paraffins (CPs) are a group of persistent organic pollutants widely applied in industrial processes, raising significant concerns regarding human internal exposure through environmental and dietary pathways. Currently, there is a lack of effective and cost-efficient methods for extracting CPs from large-scale human biomonitoring samples, and short-term variations in human internal exposure remain insufficiently characterized, particularly among the vulnerable elderly population. Here a novel, rapid, and highly efficient pretreatment method was developed to simultaneously quantify CPs of varying carbon chain lengths in minimized volumes of human plasma. This method significantly reduced the required sample volume and streamlined operational steps. It also minimized matrix effects while maintaining high accuracy and precision, enabling the simultaneous extraction of 13 very-short-chain chlorinated paraffins (vSCCPs), 24 short-chain chlorinated paraffins (SCCPs), 34 medium-chain chlorinated paraffins (MCCPs), and 35 long-chain chlorinated paraffins (LCCPs) from limited plasma samples (50 μL). The method detection limits (MDLs) and method quantification limits (MQLs) ranged from 0.02 to 1.80 ng/mL and 0.06-7.21 ng/mL, respectively. Using this method, we assessed temporal variability in internal CPs exposure across 315 plasma samples collected over 5 consecutive months from 76 healthy elderly individuals (aged 60-69) in Jinan, China. The detection frequencies were highest for SCCPs (98.73 %) and vSCCPs (90.48 %), followed by MCCPs (31.75 %) and LCCPs (16.83 %). Mean plasma concentrations were 6.12 ng/mL for SCCPs, 0.91 ng/mL for vSCCPs, 0.33 ng/mL for MCCPs, and 0.04 ng/mL for LCCPs, with a declining trend observed for vSCCPs and SCCPs over time. Correlation analysis and linear mixed-effects models (LMM) suggested that diet was the primary exposure pathway for CPs, with indoor hygiene practices also showing associations. This study provides a significant methodological advancement for biomonitoring CPs exposures, offering a powerful tool for characterizing exposure dynamics and providing a groundwork for mitigating health risks associated with these persistent pollutants globally.