Comprehensive Study of Human External Exposure to Organophosphate Flame Retardants via Air, Dust, and Hand Wipes: The Importance of Sampling and Assessment Strategy

We compared the human exposure to organophosphate flame retardants (PFRs) via inhalation, dust ingestion, and dermal absorption using different sampling and assessment strategies. Air (indoor stationary air and personal ambient air), dust (floor dust and surface dust), and hand wipes were sampled from 61 participants and their houses. We found that stationary air contains higher levels of Sigma PFRs (median = 163 ng/m(3), IQR = 161 ng/m(3)) than personal air (median = 44 ng/m(3), IQR = 55 ng/m(3)), suggesting that the stationary air sample could generate a larger bias for inhalation exposure assessment. Tris(chloropropyl) phosphate isomers (Sigma TCPP) accounted for over 80% of Sigma PFRs in both stationary and personal air. PFRs were frequently detected in both surface dust (Sigma PFRs median = 33 100 ng/g, IQR = 62 300 ng/g) and floor dust (Sigma PFRs median = 20 500 ng/g, IQR = 30 300 ng/g). Tris(2-butoxylethyl) phosphate (TBOEP) accounted for 40% and 60% of Sigma PFRs in surface and floor dust, respectively, followed by Sigma TCPP (30% and 20%, respectively). TBOEP (median = 46 ng, IQR = 69 ng) and Sigma TCPP (median = 37 ng, IQR = 49 ng) were also frequently detected in hand wipe samples. For the first time, a comprehensive assessment of human exposure to PFRs via inhalation, dust ingestion, and dermal absorption was conducted with individual personal data rather than reference factors of the general population. Inhalation seems to be the major exposure pathway for Sigma TCPP and tris(2-chloroethyl) phosphate (TCEP), while participants had higher exposure to TBOEP and triphenyl phosphate (TPHP) via dust ingestion. Estimated exposure to Sigma PFRs was the highest with stationary air inhalation (median =34 ng.kg bw(-1).day(-1), IQR = 38 ng.kg bw(-1).day(-1)), followed by surface dust ingestion (median = 13 ng.kg bw(-1).day(-1), IQR = 28 ng.kg bw(-1).day(-1)), floor dust ingestion and personal air inhalation. The median dermal exposure on hand wipes was 0.32 ng.kg bw(-1).day(-1) (IQR = 0.58 ng.kg bw(-1).day(-1)) for Sigma TCPP. The selection of sampling and assessment strategies could significantly affect the results of exposure assessment.