Persistent organic pollutants in infants and toddlers: Relationship between concentrations in matched plasma and...

Early-childhood biomonitoring of persistent organic pollutants (POPs) is challenging due to the logistic and ethical limitations associated with blood sampling. We investigated using faeces as a non-invasive matrix to estimate internal exposure to POPs. The concentrations of selected POPs were measured in matched plasma and faecal samples collected from 20 infants/toddlers (aged 13±4.8months), including a repeat sample time point for 13 infants (~5months apart). We observed higher rates of POP quantification in faeces (2g dry weight) than in plasma (0.5mL). Among the five chemicals that had quantification frequencies over 50% in both matrices, except for HCB, log concentration in faeces (C_f) and blood (C_b) were correlated (r>0.74, P<0.05) for p.p'-dichlorodiphenyldichloroethylene (p,p'-DDE), 2,3',4,4',5-pentachlorobiphenyl (PCB118), 2,2',3,4,4',5'-pentachlorobiphenyl (PCB138) and 2,2',4,4',5,5'-pentachlorobiphenyl (PCB153). We determined faeces:plasma concentration ratios (K_fb), which can be used to estimate C_b from measurements of C_f for infants/toddlers. For a given chemical, the variation in K_fb across individuals was considerable (CV from 0.46 to 0.70). Between 5% and 50% of this variation was attributed to short-term intra-individual variability between successive faecal samples. This variability could be reduced by pooling faeces samples over several days. Some of the remaining variability was attributed to longer-term intra-individual variability, which was consistent with previously reported observations of a decrease in K_fb over the first year of life. The strong correlations between C_f and C_b demonstrate the promise of using faeces for biomonitoring of these compounds. Future research on the sources of variability in K_fb could improve the precision and utility of this technique.