| Incidental ingestion of indoor dust is an important pathway for human exposure to flame retardants(FRs)and phthalate esters(PAEs).The bioaccessibility of these compounds in dust is essential for the risk assessment.In the current study,bioaccessibility of PAEs and FRs in indoor dust was measured by physiologically based extraction test(PBET).The influence of bile contents,intestinal solution pH,liquid-solid ratio,and the presence of milk powder on the bioaccessibility result was investigated.The bioaccessibility decreased with the increase of contaminant Kow with 52%for TCEP(Tris(2-chloroethyl)phosphate)and 1.5%for DEHP(Di-2-ethylhexyl phthalate).The bioaccessibility of DBP(Dibutyl phthalate),BBP(Butyl benzyl phthalate),and DEHP was positively related with bile contents,and became saturated when bile content was 10 g/L.No significant effect of bile was observed for TCEP due to the relatively higher solubility of TECP.The bioaccessibility was significantly increased in the presence of milk powder,and became stable when milk powder reached about 10 g/L.Bioaccessibility of DBP and DEHP was enhanced by the liquid-solid ratio,while not for BBP and TCEP.When pH was changed from 6 to 8,there was no significant changes for bioaccessibility of all the four contaminants.For the dust samples from offices,public microenvironments(PME),homes and dorms in Nanjing,total concentrations of organophosphate flame retardants(OPFRs)in dust samples ranged from 0.01 to 63.2?g/g,with significantly lower concentrations in dorm dust(median=0.30 ?g/g)than those in houses(3.12 ?g/g),offices(5.94 ?g/g),and PMEs(11.6).PAEs ranged from 5.49 to 2161 ?g/g with significant lower PAEs in dorm dust(379 ?g/g)than the other types of dust(767,515,and 731 ?g/g).When subject to PBET,the bioaccessibility of OPFRs ranged from 8.18%(triphenyl phosphate)to 54.5%(Tris(chloroisopropyl)phosphate),and from 1.21%(di-2-ethylhexyl phthalate,DEHP)to 81.1%(dimethyl phthalate)for PAEs.Estimated exposure dose for adults and infants to OPFRs via dust ingestion were much lower than the reference doses,but intake dose of DEHP for infants was higher than the RfD of 20 ?g/kg/d.However,the doses were safe after incorporating bioaccessibility into risk assessment.Our data indicated the importance of considering contaminant bioaccessibility during risk assessment of indoor dust.For the dust samples collected from offices,PMEs,and cars.These three types of dust were fractionated into 6 sequential size fractions,i.e.,F1:200-2000 ?m,F2:150-200 ?m,F3:100-150 ?m,F4:63-100 ?m,F5:43-63 ?m,and F6:<43 ?m.Eight polybrominated diphenyl ethers(PBDEs),six OPFRs,four novel brominated flame retardants(NBFRs),and two Dechlorane Plus isomers(DPs)were analyzed.For all the size fractions,accumulation of FRs in car dust was the highest with 12.7 and 7.6 times higher than the total FRs in office and PME dust.For FRs with Log Kow<4(i.e.,OPFRs),the distribution was inversely correlated with particle sizes,and mainly was influenced by surface area of dust particles.The accumulations of FRs with Log Kow>4 was not increased as particle size decreased,and total organic carbon eontents in dust fractions and the abrasion of FR-containing debris instead of surface area may be the influential factors.The bioaccessibility of OPFRs ranged from 1.8%to 82.3%,while bioaccessible concentrations of PBDEs,NBFRs,and DPs,due to their high hydrophobicity,were below the detection limit with only BDE209 bioaccessibility in car dust was measured as 1.3%.Bioaccessibility of OPFRs in FI fraction was significantly(p<0.05)higher than that in F6 fraction,but without significant difference among other four fractions.The cytotoxicity generally increased as the particle size decreased,and FR concentration can explain 49%of cytotoxicity based on the correlation between cytotoxicity and FR contamination values(R2=0.49,p<0.002).For the future risk assessment,the strategy of size selection for dust sampling should be standardized. |
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