The competitive nature of the dust suppression industry generally implies that they are a variety of products from different sources and feedstocks. Their inherent fingerprint and chemical structures are key to debunking their effect on the environment based on green ratings. Paramount to earth stewardship is addressing responsibility bestowed on the suppliers to produce dust suppressants and provide enough evidence of their product environmental rating in the Material Safety Data Sheet. Particularly it is important to provide a lifecycle analysis of their products once in the environment. The degradation chemistry into different products, breakdown kinetics determining the half-life and susceptibility to biodegradation provide an intricate account of the environmental perspective to use of dust suppressants. In this article we ask if enough is being done to assess claims of environmental ratings of dust control products whilst deducing chemistry of eco-friendly products as we seek to understand what the terminology actually entails in a technical sense.
Environmentally Friendly?
Initially, we ask ourselves what does environmentally friendly mean in the context of dust suppressants? The terminology presents a great rendezvous of various schools of thought and its use has led to many callous assumptions if and when not used appropriately and just as a selling point. Certainly, doing justice to the term would imply looking at how it has been used in a scientific narrative and for purposes of achieving true meaning as related to dust suppressant product development. Contrasts in source, manufacturing methods, bond chemistry and by-product alteration methods of bio-degradable dust suppressants result in degradation mechanisms and cycles varying from hours to years. The manufacturing process of dust suppressants should be environmentally rated focusing on availability of cheap feedstocks with a renewable backbone, potential for scale-up of manufacturing whilst making sure that formulation processes are mild and environmentally friendly.
Biodegradable
The two-step process of biodegradation occurs through breaking down of larger moieties into lower molecular weight species through abiotic reactions such as oxidation, photodegradation or hydrolysis in the first step. Environmentally friendly products can be degraded by bacteria, fungi or other biological means into natural elements. Furthermore, biotic reactions of microorganisms through bioassimilation breakdown the remnants by consuming, metabolizing and destroying them leading to their mineralization. Other processes such as biovolatilization involve microorganisms absorbing residues and releasing gases into the air. Emphasis is given to environmentally friendly products because bioaccumulation of non-environmentally friendly products leads to accumulation of toxins in the microbes, soil and water bodies which often leads to harm and detrimental effects on the flora, fauna and human life. Future-focused environmental good will and intent can be realized from use of green feedstocks as opposed to products consisting of metallic ions and potentially carcinogenic polyaromatic hydrocarbons. The long-term burden of dealing with these toxic components sits with the environment which gives more reason to think of dust suppressant product life cycles starting from the formulation to particular applications.
Seldom can we separate the chemistry of environmentally friendly dust suppressants from the metabolites and degradation products. Instead at a lab scale a lot of what happens in the environment can be mimicked prior environmental exposure although the variables in practice tend to present more challenges to application. Material types that are degradable include polysaccharides and fatty polyesters and their copolymers with degradation times of 14 days and 6 months to 2 years respectively. Typical examples of polysaccharides include cellulose and starch. Fatty polyesters and their copolymers such as polyglycolic acid (PGA) and polylactic acid (PLA). Cellulose degradation occurs through enzymatic oxidation of peroxidase from fungi and bacteria also participates. Owing to the substitution of cellulose derivatives such as cellulose acetate, further decomposition would have to take place under aerobic conditions. Starch on the contrary has degradation products which are non-toxic and do not require any additional degradation. PGA has a low solubility and high rate of degradation which yields acidic products whereas PLA can be hydrolyzed before microbial decomposition into lactic acid, lactic acid oligomers and carbon dioxide.
For Example…
Hydrophilic liquid polymer polyethylene glycol is used in dust control its metabolism and excretion provides an insight into its toxicological mechanisms. It is well known that an increase in molecular weight corresponds to prolonged residence time in the body and less of a change in excretion path. Oxalic acid is liberated in the degradation of ethylene glycol. The calcium salt of oxalic acid and acid metabolites such as glycolic acid have been found to pose the risk of chronic toxicity in humans. Scientists have implemented methoxy capping of polyethylene glycol to reduce the toxicity that leads to the absence of hydroxyl groups required to initiate toxicity. Another example is amphiphilic triblock copolymer poly(ethylene oxide-b-propylene oxide-b-ethylene oxide) is another water-soluble polymer that is used in dust control. Its amphiphilicity enables it to harness both hydrophilic and hydrophobic properties between water and hydrophobic surfaces. On exposure to sunlight, specifically UVA which is about 8 to 12 hours a day depending on altitude it has been noted that the half-life of the polymer is about 4 to 6 months.
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Environmentally Friendly vs Does it Work!
Preferably an ideal environmentally friendly dust suppressant must execute its mitigatory role with distinction while at its end of life it can be entirely broken down into carbon dioxide and water by environmental bugs and ultimately be incorporated into nature’s carbon cycle. Often times compromise is struck between efficacy and environmental rating which leads to short term benefits as far as the environment is concerned. It is imperative to interrogate end of life chemistry of dust suppressants and their effects to earth from production to use. There is need to challenge status quo and the very notion of the end justifies the means. This can be done through a holistic approach to safer and greener chemistry of the life cycle of environmentally friendly dust suppressants.
Connecting facts and values of environmentally friendly dust suppression whilst embracing various sound practices and their ecological impact is key to confronting the paradigm of earth stewardship from a global environmental perspective. The responsibility extends beyond just change and production of knowledge but lies in community dialogue, concrete decision making, edification, accountability and good governance. The role to play in earth stewardship is not only designated to ecologists but belongs to multiple disciplines from anthropologists, sociologists, engineers, conservation biologists, chemists and other decision-makers and citizens just to mention but a few. The ultimate goals are in the interest of environmental, economic and social sustainability at an earthly scale. The effects of dust suppressants on the environment can impact local communities therefore their participation in Earth stewardship should be at the core of scientist’s agenda whilst complementing traditional ecological knowledge.
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REFERENCES
Kangming, T., and Muhammad, B. 2020. Research progress of biodegradable materials reducing environmental pollution. Abatement of Environmental Pollutants.314-332.
Lee, T., Park, J., Knoff, D,S., Kim, K., and Kim, M. 2019. Liquid amphiphilic polymer for effective airborne dust suppression. Royal Society of Chemistry Advances. 9. 1-6.
Rozzi, R., Chaplin, F,S., Callicott, J.B., Pickett, S.T.A., Power, M.E., Armesto, J.J., and May, R.H. 2015. Introduction: Linking Ecology and Ethics for an Interregional and Intercultural Earth Stewardship. Earth Stewardship, Linking
Webster, R., Elliott, V., Park, B.K., Walker, D., Hankin, M., and Taupin, P. 2009. PEG and PEG conjugates toxicity: towards an understanding of the toxicity of PEG and its relevance to PEGylated biologicals. PEGylated Protein Drugs: Basic Science and Clinical Applications. 127-147.
