Understanding PFAS - What They Are, Their Impact, and What We Can Do

Short Summary

PFAS, a broad class of synthetic chemicals used since the 1940s, are persistent environmental pollutants with diverse classifications based on carbon chain length, head groups, and polymeric forms. The article outlines how PFAS enter the environment through industrial emissions, fire-fighting foams, domestic wastewater, biosolids land application, and landfills, and how exposure mainly occurs via diet and drinking water, with inhalation of dust as a minor route. It reviews potential health effects such as reproductive issues, cancer risk, immune and hormonal disruption, while noting substantial knowledge gaps due to the diversity of compounds. It also summarizes regulatory responses, including the U.S. EPA's final six PFAS drinking water MCLs and a Hazard Index for mixtures, and Pennsylvania's state-level PFAS rules. The original publisher is the Pennsylvania Department of Environmental Protection.

Overview

Per- and polyfluoroalkyl substances PFAS are a broad family of man-made chemicals used globally since the 1940s. They are characterized by strongly bonded carbon and fluorine chains with water-loving heads that impart persistence in the environment and a wide range of applications, from non-stick materials to firefighting foams. The article emphasizes that thousands of PFAS exist and that chemical classifications depend on tail length, fluorine content, head group, and whether compounds are simple or polymeric. Notable examples include the perfluorinated acids such as PFOA and PFOS, as well as related substances like PFHxS, PFBS, GenX chemicals, and fluorinated polymers like PTFE. The breadth of PFAS and their persistence mean that research on health and environmental effects is ongoing, with substantial knowledge gaps about specific compounds and exposure scenarios.

"PFAS are persistent environmental contaminants with thousands of compounds and diverse properties." - US EPA

According to the article, PFAS span multiple groups, including perfluorinated PFAS such as PFAAs (PFCAs and PFSAs), polyfluorinated PFAS, and polymeric PFAS. It notes that PFAS can be detected in soil, groundwater, surface water, animal tissues, and even human blood, reflecting their persistence and widespread use. While some declines in human blood levels have occurred for certain compounds after regulatory actions, the broader PFAS family remains a public health and environmental concern.

Key PFAS forms highlighted include PFOA, PFOS, PFHxS, PFNA, GenX (HFPO-DA), NBPs (Nafion byproduct 2), PFMOAA, FOSAs, PASFs, PFAIs, and PAFs, as well as fluorinated polymers like PTFE and PVDF. The classification framework underscores the diversity of PFAS and the complexity of assessing risk across the spectrum of compounds and polymeric materials.

Environmental Pathways and Human Exposure

The article outlines several pathways by which PFAS reach the environment, beginning with industrial emissions from manufacturing and use, including wastewater effluents, spills, and leaks. Aqueous film-forming foams AFFFs used to extinguish high-hazard fires are a notable PFAS source that can contaminate soil, groundwater, and surface water during training, response events, and routine operations at airports, military facilities, chemical plants, shipyards, and refineries. Domestic wastewater containing PFAS from consumer products can be treated at municipal or private facilities, with removal efficiencies varying by compound, potentially releasing PFAS into soil and water via treated effluent. Biosolids generated during wastewater treatment, when applied to land, can transfer PFAS to soils, with concentrations dependent on the wastewater input and treatment technologies; exceptional quality biosolids may be used in gardens and landscaping, while contaminated biosolids may pose environmental risks. Leachate from landfills can also carry PFAS into surrounding environments, depending on landfill management and leachate treatment.

Exposure to PFAS in humans occurs primarily through diet and drinking water, with inhalation of PFAS-containing dust as a secondary route. PFAS have been detected globally in soil, groundwater, surface water, animal tissues, and human serum, reflecting their persistence and widespread use.

"Industrial emissions and AFFFs have contributed to PFAS release to soil, groundwater, and surface water" - Dasu et al., 2022

Exposure, Health Impacts, and Regulations

Dietary exposure through drinking water is a central concern. A nationwide USGS study found that about 45% of public tap water systems contain at least one PFAS compound. Private wells require individual testing and treatment decisions, and state programs such as Pennsylvania’s provide accredited labs and testing guidelines for potable water. Treatment options at the point of use or entry include granular activated carbon GAC, ion exchange resins, and reverse osmosis, with device operation and maintenance crucial for effectiveness. The National Health and Nutrition Examination Survey NHANES has shown declines in some PFAS blood levels after phase-outs of PFOS and PFOA, but health effects remain uncertain and may vary by dose, duration, and compound, with gaps in knowledge regarding reproductive, immune, hormonal, and cancer risks.

"Exposure routes include dietary intake and drinking water, with inhalation of PFAS-contaminated dust as a secondary pathway" - ATDSR, 2019

Regulatory action has progressed at the federal and state levels. On April 10, 2024, the US EPA issued final National Primary Drinking Water Regulations for six PFAS with enforceable MCLs: PFOA 4.0 ng/L, PFOS 4.0 ng/L, PFHxS 10 ng/L, PFNA 10 ng/L, GenX HFPO-DA 10 ng/L, and a hazard index for mixtures containing two or more of PFNA, HFPO-DA, PFHxS, and PFBS set at 1. Public water systems have until 2029 to monitor finished water and implement treatment to meet these standards; the MCLs do not apply to private wells. Interim health advisory levels for certain PFAS were issued in 2022. In September 2023, EPA finalized a rule requiring manufacturers and importers of PFAS and PFAS-containing articles since 2011 to report information to EPA on chemical identity, uses, volumes, byproducts, health effects, worker exposure, and disposal. Pennsylvania has its own PFAS MCL rule for PFOA and PFOS in drinking water (PFOA 14 ng/L; PFOS 18 ng/L), which is higher than the federal MCLs.

"There are knowledge gaps on specific human health effects exist given that there are a wide variety of PFAS chemicals in use and overall individual exposure routes and exposure durations can vary" - Panieri et al., 2022

PFAS in Agricultural Systems and Management Strategies

PFAS can reach agricultural soils through the land application of biosolids. Some states, such as Michigan, have interim strategies to limit land application of PFAS-impacted biosolids and promote testing and management strategies on farms, including soil and water testing and the use of uncontaminated plots or water sources. There are no universal federal or state regulations specifically governing PFAS in agricultural soils. If PFAS are detected in animal products, investigations into feed and water sources are recommended, with exposure reduction leading to gradual declines in concentrations, though the rate of decline varies by animal species.