Hydroxylated polybrominated diphenyl ethers (OH-PBDEs) in biosolids from municipal wastewater treatment plants in China

► OH-PBDEs were determined in sewage sludge for the first time. ► 6-OH-BDE-47 was the most predominant congener in sludge, followed by 2′-OH-BDE-68. ► Concentrations of OH-PBDEs were higher in coastal areas than inland regions. ► A significant linear relationship was found between 6-OH-BDE-47 and 2′-OH-BDE-68.