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A circular economy Part Three: the air we breathe

Updated: Apr 6, 2023

The first two blogs in this series focused on stormwater and food waste as examples of media contaminated with the complex mixture of chemicals emitted from day-to-day products such as paint, road sealants, plastics, and food packaging. These chemicals present a hazard to ecosystems―urban, agricultural, and otherwise—into which they are emitted.

With this background, it’s not so surprising to learn that the air we breathe―particularly indoors—is also contaminated with a complex mixture of chemicals. From polychlorinated biphenyls (PCBs) to pesticides like chlordane, the air of our homes contains a complex mixture of chemicals sourced from the pesticides, surfactants, cosmetic products, pharmaceuticals and drugs, flame retardants, plasticisers, per- and poly-fluorinated compounds, and UV blockers that make up the products we use inside and in the vicinity of houses. While this is alarming in many ways given the outcomes of research on just some groups of these chemicals, the products that act as sources of these chemicals and the chemicals themselves are not the focus of this blog. Instead, the focus is on how recycling and landfilling the products we use in our homes act as sources of pollution to the environment as a whole.

Of the different environmental compartments that are both sources and sinks for contamination—that is soil, water, and air―it is air that is the least studied.

Shutterstock Stock Photo ID: 1014295147

Like soil and water, different components of the air are contaminated to different degrees and, when talking about air pollution, it’s important to know which aspect of the air is the focus. Within water, for example, the sediments that are entrained in the water column and that make it turbid are likely to contain different concentrations and different chemicals than the water that surrounds the sediment. Similarly, the clay fraction of soils, with its very high surface area, is more likely to be contaminated than the sand fraction of soils. So too is the case with air, where contaminants can occur in the gas phase, or be sorbed or partitioned onto total suspended solids or to particulate matter, usually measured in the 1, 2.5, or 10 µm diameter range. The type of contaminant and its concentration within different air components then depends on the nature of the particulate matter and the chemical properties of the contaminant of concern.

The type and degree of air contamination also depends on the contamination source, with recycling facilities—including those in highly regulated “western” countries—found to be sources of key emerging contaminants of concern. Perhaps the best studied example of such contamination is recycling facilities as a source of polybrominated diphenyl ethers (PBDEs) to the atmosphere. For example, research in the United States found that both an electronics recycling facility and an automotive shredder were key sources of PBDEs to air in the surrounding environment. Similar results were found in Canada, where e-waste recycling facilities were considered to be a key source of flame retardants to the atmosphere, including PBDEs, organophosphate esters, chlorinated flame retardants, and novel brominated flame retardants (NBFRs).

Research conducted in Melbourne, Australia instead found that PBDEs were no longer strongly associated with electronic waste recycling facilities, with NBFRs—a chemical group with similar hazard properties to PBDEs―instead being the key contaminants of concern. In another Australian study, landfill sites were also found to be key sources of NBFRs to soils. These soils, once entrained as dust into the air, then become atmospheric pollutants.

While the recycling of electronic wastes is a key source of contamination to the air, the disposal of household items to landfills also creates atmospheric pollution. Like the Australian study, a study in the USA also showed a direct link between landfills and air contamination. In this study, however, gaseous per- and poly-fluoroalkyl substances (referred to in that study as per fluorinated substances, PFS) and synthetic musk fragrances were generated by landfills. Synthetic musks are a group of chemicals that are a key ingredient of perfumes, deodorants, and detergents, and that contains some chemicals that are a risk to the environment. In fact, landfills account for 10% of volatile organic compound emissions to the air in the USA. These emissions include a wide variety of hazardous chemicals, including xylenes and toluene from personal care products, limonene and dichlorobenzene from cleaning products, and benzene and formaldehyde from furniture.

The factoids in the previous paragraphs all relate to one key point: the myriad of products we use in our every-day lives are not designed with their end of use in mind. With the exceptions of some regulated wastes, the processes of recycling, reusing, and landfilling the items we use in our day to day lives are seldom designed to minimise the hazards to air, soil, and water presented by chemicals in the products.

In this series of blogs, the often-ignored policy conflict between risks from chemicals in the recovered, reused, and recycled products and the need to decrease resource consumption has been highlighted. Policies that encourage recycling inherently increase the risks to human health and the environment from hazardous chemicals by recycling these chemicals back into the economy or releasing them into the environment. While the scientific literature is replete with examples of how this conflict manifests, the need to address both resource consumption and chemical hazards is being addressed, especially in Europe where much of the work to minimise resource consumption and chemical risks seems to currently occur. My hope is that the current drives for a circular economy in Australia, Aotearoa, and elsewhere―including the reuse of biosolids, greywater, stormwater, as well as the recycling of products and materials that are consumed—properly account for the hazardous chemicals that are used in our societies. There’s no denying resource consumption must be vastly decreased in our society; but so too must our exposure to chemical hazards.

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