Flame retardant
[14] Intumescent additives are often employed; their role is to turn the polymer surface into a char, which separates the flame from the material and slows the heat transfer to the unburned fuel.
Non-halogenated inorganic and organic phosphate flame retardants typically act through this mechanism by generating a polymeric layer of charred phosphoric acid.
Cotton is typically made flame-resistant by chemical applications of polymeric, nonpolymeric, and polymeric/nonpolymeric hybrids that are composed of one or more of the elements such as nitrogen, sodium, phosphorus, silicon, boron, or chlorine.
Typically, their undergarments beneath the heavier fire-resistant gear are made of flame-retardant cotton or another breathable, organic fabric that has been treated to resist ignition.
[22] In 1975, California began implementing Technical Bulletin 117 (TB 117), which requires that materials such as polyurethane foam used to fill furniture be able to withstand a small open flame, equivalent to a candle, for at least 12 seconds.
In order to make the evaluation fully comprehensive, it was decided to compare also material and fire performance as well as attempt a life-cycle assessment of a reference product containing halogen free versus brominated flame retardants.
About a dozen halogen free flame retardants were studied representing a large variety of applications, from engineering plastics, printed circuit boards, encapsulants to textile and intumescent coatings.
A large group of the studied flame retardants were found to have a good environmental and health profile: ammonium polyphosphate (APP), aluminium diethyl phosphinate (Alpi), aluminium hydroxide (ATH), magnesium hydroxide (MDH), melamine polyphosphate (MPP), dihydrooxaphosphaphenanthrene (DOPO), zinc stannate (ZS) and zinc hydroxstannate (ZHS).
However, moulded plates which represent real world plastic products showed much lower leaching levels than extruded polymer granules.
The impact assessment studies reconfirmed that the improper waste and recycling treatment of electronic products with brominated flame retardants can produce dioxins which is not the case with halogen free alternatives.
Watersheds that include the Southern California Bight, Puget Sound, the central and eastern Gulf of Mexico off the coast of Tampa and St. Petersburg, in Florida, and the waters of Lake Michigan near Chicago and Gary, Indiana, also were found to have high PBDE concentrations.
[45] There is a potential association between the exposure to the Phosphorus Flame Retardants (PFR) in residential indoor dust and the development of allergies, asthma and dermatitis.
[46] Another study conducted by Chevrier et al. 2010[47] measured the concentration of 10 PBDE congeners, free thyroxine (T4), total T4, and thyroid-stimulating hormone (TSH) in 270 pregnant women around the 27th week of gestation.
A prospective, longitudinal cohort study initiated after 11 September 2001, including 329 mothers who delivered in one of three hospitals in lower Manhattan, New York, was conducted by Herbstman et al.
[48] Authors of this study analyzed 210 cord blood specimens for selected PBDE congeners and assessed neurodevelopmental effects in the children at 12–48 and 72 months of age.
Results showed that children who had higher cord blood concentrations of polybrominated diphenyl ethers (PBDEs) scored lower on tests of mental and motor development at 1–4 and 6 years of age.
A similar study was conducted by Roze et al. 2009[49] in The Netherlands on 62 mothers and children to estimate associations between 12 Organohalogen compounds (OHCs), including polychlorinated biphenyls (PCBs) and brominated diphenyl ether (PBDE) flame retardants, measured in maternal serum during the 35th week of pregnancy and motor performance (coordination, fine motor skills), cognition (intelligence, visual perception, visuomotor integration, inhibitory control, verbal memory, and attention), and behavior scores at 5–6 years of age.
Study also found that lower maternal education was independently and significantly associated with higher levels of most flame retardant congeners in the children.
A 2009 in vivo animal study conducted by the US Environmental Protection Agency (EPA) demonstrated that deiodination, active transport, sulfation, and glucuronidation may be involved in disruption of thyroid homeostasis after perinatal exposure to PBDEs during critical developmental time points in utero and shortly after birth.
[56] Some halogenated flame retardants, including the less-brominated PBDEs, can be direct neurotoxicants in in vitro cell culture studies: By altering calcium homeostasis and signalling in neurons, as well as neurotransmitter release and uptake at synapses, they interfere with normal neurotransmission.
[77] Mothers thyroid hormone (T4) level can be disrupted[78] and exposure in utero in rat studies has been demonstrated to alter motor control, delay sensory development and puberty.
Young children crawling and playing on the floor frequently bring their hands to their mouths, ingesting about twice as much house dust as adults per day in the United States.
A study was conducted by Carignan in 2013, C. et al. found that gymnasts are exposed to some flame-retardant products such as PentaBDE and TBB more than the general population in the United States.
The flame retardant industry has developed a voluntary initiative to reduce emissions to the environment (VECAP)[87] by promoting best practices during the manufacturing process.
Communities near electronics factories and disposal facilities, especially areas with little environmental oversight or control, develop high levels of flame retardants in air, soil, water, vegetation, and people.
[22] When wearing Personal Protection Equipment (PPE) and when a ventilation system is installed, exposure of workers to dust can be significantly reduced, as shown in the work conducted by the recycling plant Stena-Technoworld AB in Sweden.
[93] Brominated flame retardants may also change the physical properties of plastics, resulting in inferior performance in recycled products and in “downcycling” of the materials.
Further legislation in California has served to educate the public about flame retardants in their homes, in effect reducing consumer demand for products containing these chemicals.
According to a law (Senate Bill, 1019) signed by Governor Jerry Brown in 2014, all furniture manufactured after January 1, 2015 must contain a consumer warning label stating whether it does or does not contain flame retardant chemicals [94] As of September 2017, the topic reached federal regulatory attention in the Consumer Product Safety Commission, which voted to put together a Chronic Hazard Advisory Panel focused on describing certain risks of various consumer products, specifically baby and childcare products (including bedding and toys), upholstered home furniture, mattresses and mattresses and mattress pads, and plastic casings surrounding electronics.
[95] Pursuant with the Toxic Substances Control Act of 1976, the Environmental Protection Agency is also actively evaluating the safety of various flame retardants, including chlorinated phosphate esters, tetrabromobisphenol A, cyclic aliphatic bromides, and brominated phthalates.
