# PFAS: The Journey from Wonder Chemicals to Environmental Nightmares and the Search for Solutions
## 3 Human Exposure and Health Impacts  
As discussed, earlier PFAS can be present in our drinking water (both public and private drinking water wells), soil, landfills, waste disposal sites and hazardous waste sites, food or food packages like pizza boxes and candy wraps, household products like fabric, cook-ware and cleaning products and firefighting foams [56]. The major source of PFAS waste is from industrial and municipal WWTPs where this can be directly contributed to the PFAS in the atmosphere and freshwater systems and indirectly spread into the sewage, sludge, and biosolids for agricultural use [6; 79]. Figure 2 illustrates the environmental distribution of PFAS and possible human and environmental exposure pathways. Untreated PFAS has become a major issue due to the widespread environmental presence, bioaccumulation, persistence, and adverse health effects as they can end up in plants and food chain [80]. A study showed that several PFAs were detected with the ng/L concentration range and perfluorooctanoic acid (PFOA) with a median concentration of 67 ng/L to 697 ng/L, in an effluent in the WWTPs in New York. This high persistence of PFAA in the environment and the widespread detection creates concerns about possible human and animal PFAS exposure. Due to the irreplaceability of some applications in some PFAs and fluorinated PFAS alternatives, detecting and evaluating the environmental impacts of PFAS-related substances has become a primary concern. It has become a major risk to humans and other living organisms as these chemicals can enter the human body through digestion and respiratory systems and accumulate in the body [81; 82]. Drinking water exposure is identified as one of the most concerning pathways [68; 83]. Recent studies using human blood samples have found PFOS, PFOA, perfluoronanoate acid (PFNA), and perfluorohexane sulfonic acid (PFHxS) in human serum and plasma proteins. Some of these chemicals were detected in animal blood samples collected in remote regions of the world and due to the widespread occurrence and health effects, major U.S. companies have terminated PFOS and PFHxS production in 2002. Due to the unique structure, most PFAS substances remain untreated at the WWTPs, and the effluent from WWTPs or untreated sewage discharges to the environment or landfill. Therefore, both WWTPs and landfill leachate are two major sources of releasing PFAS into the aquatic environment. For many decades, landfills have been identified as a long-term disposal of solid waste from residential, commercial, and industrial sources and PFAS have been detected in both historic and active landfills [1; 54; 75]. [PERSON] et al. reported that landfill leachate and effluent of WWTPs have PFAS concentrations of 93,100 ng/L and 6950 ng/L. Before 2002, US EPA set the drinking water health advisory limits for PFOS and PFOA to 150 ug/L and 1 ug/L and it was reduced to 0.2 ug/L and 0.4 ug/L in 2009 and further reduced to a combined value of 70 ng/L in 2016 [84]. PFOA and PFOS are still present in significant concentrations and some short-chain PFAS substances like HFPO-DA(GenX), PFHxA, PFHxS, and PFBA have been detected in drinking water sources and tap water worldwide. This can lead to chronic exposure and bioaccumulation and the human population consuming a larger amount of PFAS-contaminated drinkingwater for a longer period can cause major health problems, such as alternations in lipid metabolism, kidney, and testicular cancer, impaired liver functions, chronic kidney damage, cardiovascular disease, pregnancy-induced hypertension or pre-eclampsia, reduced fetal growth, preterm birth, low birth weight, childhood obesity, and increased miscarriage risk [79; 85; 86]. When considering the environmental persistency and health impacts, particle size plays an important role as the composition. Size fraction information involves analyzing PFAS particles or aggregates based on their size distribution. This can influence the transport and mobility in the environment and the bioavailability and potential uptake by organisms.