Risk assessment of the presence of polycyclic aromatic hydrocarbons (PAHs) in coastal areas of Thailand affected by the 2004 tsunami

•PAHs in soils and sediments in 2004 tsunami-affected area of Thailand were analyzed for the first time.•Generally, ∑12PAHs in this study were much lower than values observed for sediments around the world.•The risk levels of PAHs fall in the “acceptable” range of the US EPA model. The total concentrations of twelve, likely carcinogenic, polycyclic aromatic hydrocarbons (PAHs) (i.e., phenanthrene (Phe), anthracene (An), fluoranthene (Fluo), pyrene (Pyr), benz[a]anthracene (B[a]A), chrysene (Chry), benzo[b]fluoranthene (B[b]F), benzo[k]fluoranthene (B[k]F), benzo[a]pyrene (B[a]P), indeno[1,2,3-cd]pyrene (Ind), dibenz[a,h]anthracene (D[a,h]A), and benzo[g,h,i]perylene (B[g,h]P) in backwash deposits of the 2004 Khao Lak tsunami were carefully investigated and compared with the concentrations of world marine sediments (WMS). In general, ∑12PAHs in this study (i.e., 69.43±70.67ngg−1) were considerably lower than those values observed in marine sediments from Boston (54,253ngg−1), coastal sediments from Barcelona Harbour (15,069ngg−1), and riverine sediment from Guangzhou Channel (12,525ngg−1), but were greater than values from coastal sediments in Rosas Bay (12ngg−1), Santa Ponsa Bay (26ngg−1) and Le Planier (34ngg−1). The total toxic benzo[a]pyrene equivalent (TEQCarc) values calculated for Khao Lak coastal sediments (KCS), Khao Lak terrestrial soils (KTS), and Songkhla Lake sediments (SLS) were 10.3±12.2ngg−1, 16.0±47.7ngg−1, and 5.67±5.39ngg−1, respectively. Concentrations of PAHs at all study sites resulted in risk levels that fell into the “acceptable” range of the US EPA model and were much lower than those of other WMS. The cancer risk levels of PAH content in KCS ranged from 7.44×10−8 to 2.90×10−7, with an average of 1.64×10−7±8.01×10−8; this value is 119 times lower than that of WMS. In addition, soil cleanup target levels (SCTLs) for both non-carcinogens (i.e., Phe, An, Fluo and Pyr) and carcinogens (i.e., B[a]A, Chry, B[b]F, B[k]F, B[a]P, Ind, D[a,h]A and B[g,h,i]P) in the KTS samples were estimated for all target groups, with an average value of 115,902±197,229ngg−1.