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With more than 4,000 individual PFAS compounds present in a variety of industrial or consumer products, we are at stage where our ability to measure these compounds far exceeds our understanding of the potential health impacts and our ability to communicate human health risks when the compounds are found in the environment. In a collaboration between North Carolina State and Oregon State Universities, we are currently measuring PFAS in landfill gas from about 25 landfills across the U.S. Michael A. Abraczinskas: PFAS challenges for environmental regulatory agencies This critical review of PFAS exposures in humans is timely and deserves considerable attention due to concerns over toxicity and persistence in the environment. Michael Kleinman: PFOA and PFAS: toxicology and mechanistic considerations Perfluorooctanoic acid (PFOA) and Perfluoroalkyl substances (PFAS), which are used in many commercial applications, are persistent in the environment, do not readily undergo chemical degradation or biotransformation, bioaccumulate and are found, not only in the serum of occupationally exposed workers, but also the blood and tissues of the general population (Kudo and Kawashima [48]; Sanchez Garcia et al. [63]) including children and adolescents (Duffek et al. [25]). Many PFAS and PFOA compounds degrade to acid forms (PFAAs), environmental exposures are often to mixtures of compounds and toxic potential (potency) can vary across the family of compounds. [Extracted from the article]

People in polluted communities are often exposed to both PM and ozone (O3), albeit not always simultaneously; an important question is whether exposure to particles with seasonal compositional differences can influence biological outcomes. We addressed this question using a mouse model of cardiovascular disease by contrasting the health outcomes of exposures to particles formed or aged during periods of relatively high photochemical activity (i.e. spring/summer), which has increased ambient O3 concentrations, with outcomes of exposures to fall/winter particles which are associated with lower O3 concentrations. Electrocardiographs (ECGs) and blood pressures (BPs) were acquired following exposures to concentrated ambient particles (CAPs). ECGs were analyzed to changes in specific waveform parameters and changes in heart rate variability (HRV). Exposures elicited several types of waveform abnormalities that were associated with seasonal differences in particle constituents. Alterations in R-R interval and P-R interval were seen following exposure to summer CAPs but not fall CAPs and differential responses were seen in the corrected Q-T interval following the two seasonal exposures. Measures of HRV increased after exposure to summer CAPs compared to air-exposed controls but not following the winter CAPs exposure. There were chemical differences with respect to the organic constituents in ambient particles between summer and fall aerosol. The oxygen to carbon ratios (O:C) were generally higher in the spring and summer than in the fall, consistent with seasonal differences in atmospheric photochemical activity. Seasonal differences in atmospheric photochemical activity can modify ambient aerosol composition and can alter biological responses in the cardiovascular system. The results from this study confirm that ambient photochemical activity can alter the toxicity of ambient PM. Regional and seasonal differences in PM2.5 composition should be important considerations when evaluating the effects of PM exposure on cardiovascular health. Implications: Particles formed during periods of high photochemical activity (e.g. spring/summer) elicit more adverse cardiovascular health effects than particles formed during periods of low photochemical activity (e.g. fall/winter). Seasonal differences in atmospheric photochemical activity modified ambient aerosol composition and worsened cardiovascular responses. These results can inform regulatory agencies and may help design air quality regulations for PM2.5 that consider seasonal and regional variations. [ABSTRACT FROM AUTHOR]

The article presents comments on several articles related to the issues of air quality and climate change. Professor Michael T. Kleinman discusses hydrofluorocarbons and the health aspects of multiple air pollutants that contribute to fine particles and ozone. Howard J. Feldman tackles the link between climate change and pollutant buildup. J. Jason West elaborates on the interconnections between air pollution and climate change.

Graph: Michael T. Kleinman Graph: Eric D. Stevenson Per- and polyfluoroalkyl substances (PFAS) are a complex class of chemical contaminants that include perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS), all of which are compounds that are extremely stable and persistent in the environment. Although the exact mechanisms are not fully understood, PFAS toxicity can cause increased oxidative stress, changes in gene expression, and immune suppression, all of which have been described as key characteristics of carcinogens that affect humans; thus, PFAS may pose significant risks as toxic contaminants and carcinogens. The discussants - Michael Abraczinska, Xuelian Bai, Morton Barlaz, Virginia Guidry, and Alex Lan - will provide different perspectives, and may agree or disagree with the conclusions and recommendations of the Critical Review and with one another. [Extracted from the article]

The article discusses the 2014 Critical Review discussion by the Air and Waste Management Association in the U.S. The discussion was centered on relationships between air pollution and human health, with an emphasis on an important component of regulated particulate matter (PM) PM2.5 and PM10 exposure. The discussants include Daniel S. Greenbaum, Ronald E. Wyzga, and Michael T. Kleinman.