The researchers studied the presence and behavior of flame retardant chemicals in different types of wastewater treatment plants and nearby rivers in Korea. They found that industrial wastewater had the highest levels of these chemicals, especially TBBPA. The treatment process was most effective at removing PBDEs, with lower removal rates for HBCDs and TBBPA. Interestingly, the levels of PBDE metabolites actually increased in human wastewater after treatment, suggesting they may transform during the process. Overall, PBDEs were most common in sewage, while TBBPA was more prevalent in industrial wastewater.