In recent years, fire initiation caused by a lack of fireproof measurements has been one of the leading causes of casualties and property damage. Taking the Grenfell Tower fire as an example, the fire incidence occurred in North Kensington on 14 June 2017 with 74 deaths identified. Under investigation, the tragedy was believed to be caused by inappropriate usage of building materials for the rainscreen cladding indoor, which, was flammable and eventually led to a quick spread of fire. Inspired by this issue, we have made some research on fire retardants.
What are fire retardants?
Fire retardants are substances designed to prolong escape time during a fire accident. In general, the fire retardants enable the prevention of fire spreading when combined with certain combustible and flammable materials, including bed sheets, furniture, electronic devices, and building materials. However, current fire retardants are imperfect, comprised of hazardous chemicals that may impair our health and the environment. Thus, the development of novel fire retardants with environmental-friendliness is desirable to popularize effective fire retardants and ultimately improve the current fireproof materials.
Fire retardants are most commonly divided into three groups based on their properties and chemical structure, namely Organohalogen Flame retardants, Nitrogen flame retardants, and Phosphorus. Due to their different chemical properties, their flame retardancy mechanism is also diversified (Endothermic degradation, the establishment of thermal insulation barrier, Dilution of the gas phase, Gas-phase radical quenching).
Threats to human
There are hundreds of different flame retardants. However, considering their flaws and the need for future improvements, here we introduce you to the harm of Inorganic and halogen fire retardants, which occupies the majority of the current flame retardants.
Inorganic fire retardants
At present, inorganic fire retardants display a predominance in the fire retardants market. Yet, their composition is likely to contain hazardous chemicals including antimony trioxide, boric acid, zinc borate, decabromodiphenyl oxide, and melamine which claims to consist of health effects to humans under the Federal Hazardous Substances Act (FHSA). In general, these toxic chemicals may induce cancer, neurodegenerative diseases, and organ failure.
|Chemical||Acute Toxicity||Chronic Toxicity|
|Antimony Trioxide (Oral)||Toxic|
|Antimony Trioxide (Inhalation)||Toxic|
(1)Antimony Trioxide (2)TBBPA (3)PBDEs
Production of waste
Inorganic flame retardants are known to be used independently or in conjunction with other types of flame retardants for effectiveness. Of which, Aluminum Hydroxide is known as the largest consumed product type. In the generation of Aluminium Hydroxide, the process typically involves the refinement of bauxite into alumina. However, the manufacturing process often leaves a significant amount of solid waste by-product called Bauxite tailings. With the established demonstration that these by-products are usually stored in disposal sites near the production facilities, it enhances the potential of causing leaching and heavy metal run-off. Moreover, these by-products may lead to causing secondary effects, like deforestation, soil erosion, an increase in water turbidity, and disturbance of the hydrology cycle.(4)
In addition, there are also those traditional fire retardants which are made of organohalogen compounds. As the most well-known ones, “Bromine Flame retardants”, among the class including chlorine-based ones, such as TBBPA, PBDEs, PCBs, HBCDs, etc. According to researchers, they are ubiquitous persistent organic pollutants and bioaccumulates in the environment. In acknowledgment of their interaction as either antagonists or agonists at receptors sites of androgen, progesterone, and estrogen, these all indicate that the listed compounds may act as potential endocrine disruptors. Not mentioning their ability on establishing certain developmental neurotoxicants that cause behavioral alterations. These organohalogen compounds, for example, TBBPA, PBDEs, and PCBs include serious impacts on our motor activity and cognitive functions. As mentioned impacts can cause serious concerns toward the growth of babies due to the presence of toxicants in human breast milk, these irreversible influences are one of the major threats taken into account.(1)
Not only causing harm to humans, but these traditional fire retardants can also bring side effects to the environment. For example, Bromine is used to produce ⅕ of the world’s supply of fire retardants, and the only way to acquire bromine is through brine mining. As a consequence of brine mining, it can greatly influence the agriculture industry and public water supply. Therefore, impacting fresh groundwater resources due to over-pumping. Pollutions are also made because of emulsified or dissolved organic compounds (heavy and light hydrocarbons, phenols, ketones), chemical additives (surfactants, biocides, scale inhibitors, corrosion inhibitors), bacteria, metals (zinc, lead, manganese, iron, barium) and naturally occurring radioactive materials. (2) (3)
The Stockholm Convention and its exemption
To protect human health and the environment from the effects of persistent organic pollutants, an international environmental treaty, Stockholm Convention on Persistent Organic Pollutants was signed in 2001 and effective from May 2004.
Despite certain chemicals being banned, some countries take advantage of a loophole in the Stockholm Convention that allows the banned chemicals in recycling and requested an exemption for prolonged use. For example, PBDE flame retardant chemicals were banned a decade ago but Brazil, Japan, South Korea, and Turkey, still allow this class of chemicals to continue to contaminate consumer goods made from recycled plastics, with no plan to terminate (A). HBCD is another banned flame retardant example, with multiple studies finding potential effects on liver and thyroid function and the endocrine system (B). China still allow the production, use, import, and export of HBCD used for expanded polystyrene and extruded polystyrene in buildings (used mainly as flame retardant) (C).
Instead of prohibiting all such dangerous, persistent organic chemicals in furniture, etc, governments allow different hazardous pollutant(s) to be replaced by others. Inspired by this issue, we aim to overcome these problems by the development of an engineered recombinant e.coli strain which is utilized for a sequential production of flame retardant protein. Through synthetic biology, we hope to develop a novel flame retardant protein with lower production costs and less toxic chemicals in order to reduce the threats to human health and the environment. As a result, a sustainable and environmentally friendly flame retardant is developed and is promising to replace the current flame retardant in the hope of eventually protect humans from fire initiation.
Herein, we separated our project into two parts. The first part is the expression of our fire retardant protein. The protein is composed of human SR protein, alpha-casein protein, which is iGEM parts registered by the previous 2015 Mingdo iGEM team and the 2019 Duesseldorf's iGEM team, respectively.
The second part is the application of our fire retardant protein in different aspects. As long-period retention of our protein on different surfaces is a crucial factor of the protein‘s fire retardancy, the fusion of the flame retardant protein with strong adhesive protein, such as mussel adhesive protein or cellulose-binding domain would be favorable to increase the fire retardant protein’s retention ability on different surfaces, thus improve its fire retardancy.
1. Lucio G. Costa, Gennaro Giordano, Sara Tagliaferri, Andrea Caglieri, Antonio Mutti. Polybrominated diphenyl ether (PBDE) flame retardants: environmental contamination, human body burden and potential adverse health effects. ACTA BIOMED 79: 172-183; 2008
2. Yanosky, T. M., & Kappel, W. M.. Effects of solution mining of salt on wetland hydrology as inferred from tree rings. Water Resources Research, 33(3), 457–470; 1997
3. Sun, M., Lowry, G. V., & Gregory, K. B. Selective oxidation of bromide in wastewater brines from hydraulic fracturing. Water Research, 47(11), 3723–3731; 2013.04.041
4. Ma, D., Wang, Z., Guo, M., Zhang, M., & Liu, J. Feasible conversion of solid waste bauxite tailings into highly crystalline 4A zeolite with valuable application. Waste Management, 34(11), 2365–2372; 2014.07.012