Feature Image: Photo credit: https://pixabay.com/photos/industry-sunrise-air-pollution-1752876/
Source Article: Rauert, C., Shoieb, M., Schuster, J.K., Eng, A., Harner, T. 2018. Atmospheric concentrations and trends in poly- and perfluoroalkyl substances (PFAS) and volatile methyl siloxanes (VMS) over 7 years of sampling in the Global Atmospheric Passive Sampling (GAPS) network. Environmental Pollution Volume 238, pages 94-102. https://doi.org/10.1016/j.envpol.2018.03.017
What are PFAS and VMS?
PFAS (chemical name: per- and polyfluoroalkyl) are a group of man-made chemicals that have been used in a variety of products since the 1940s. These chemicals, which can be found in food, food packaging, household products (e.g. cookware), drinking water, and living organisms have gained increasing attention over the past few decades because research has shown they have negative impacts on organisms and human health. PFAS can have negative impacts on the immune system, liver, and kidneys. Additionally PFAS exposure has been linked to increased cholesterol levels, low infant birth weights, and tumors.
Similarly, VMS (chemical name: volatile methyl siloxanes) are a separate group of man-made chemicals, commercially produced since the 1940s, that are used in products such as pesticides, sealants, cleaning products, hair/skin products, deodorants, and pharmaceuticals. Due to their wide spread use, VMS are produced in mass quantities each year and have been detected regularly in the environment. Studies have shown that certain VMS can be toxic to aquatic organisms, including fish and invertebrates (for review of VMS toxicity see Wang et al. 2013).
Monitoring global air quality
Due to the over exposure to PFAS, VMS, and countless other man-made chemicals, significant efforts have been made to monitor and measure the concentrations of these chemicals in the air throughout the globe. One such effort, the Global Atmospheric Passive Sampling (GAPS) network, began in 2004 and samples the atmosphere at more than 50 sites on 7 continents. This program allows scientists to determine trends in air quality, screen for new chemicals in the air, and assess the long-range transport of air pollution across the globe.
How have pollutants in the atmosphere changed from 2009 to 2015?
Leveraging the data from the GAPS network, Cassandra Rauert and her colleagues at Environment and Climate Change Canada aimed to determine how PFAS and VMS had changed in the atmosphere using sampling data at 21 sites from 2009, 2013, and 2015. These sites were located in Australia, Europe (e.g. Czech Republic, Norway, Ireland, France), Bermuda, and North America (Canada, United States). Sampling sites were classified as urban, polar, or background.
The researchers found that the concentration of VMS is the atmosphere were elevated compared to PFAS, likely due to the fact that VMS are produced on a mass scale and continuously emitted into the atmosphere. For example, China alone produced over 270,000 tons of the VMS polysiloxane in 2009 (Wang et al. 2013). While some VMS chemicals showed a decrease in concentration in the atmosphere between 2009 and 2015, a class of chemicals known as cyclic VMS increased by a factor of 6 at polar sites. The researchers suggest that this may reflect a shift in the production of VMS to favor cyclic VMS over other chemicals.
The researchers reported that concentrations of some types of PFAS remained constant in samples from 2009, 2013, and 2015, but others, namely the PFSAs (perfluoroalkane sulfonates) significantly increased from 2013 to 2015. Furthermore, the concentration of PFSAs was higher in urban areas in 2015, which indicates that there may be new sources of emissions close to these areas. PFSAs are commonly found in pizza boxes, microwave popcorn bags, and cosmetics.
Future research directions
This research highlights the importance of intensive global monitoring efforts. The researchers note the importance of future monitoring efforts which will help scientists determine continued changes in atmospheric chemicals and inform management and regulatory efforts. PFAS compounds are currently regulated under the Stockholm Convention on Persistent Organic Pollutants (POPs), but as this research shows, there has been no significant decrease in these chemicals in the atmosphere. Future sampling efforts need to be conducted to examine the continued changes of these chemicals in the atmosphere and steer future regulatory efforts.