Discussions article by polymer chemicals researcher suggests effective phosphorus flame retardants may have low toxicity. Bob Howell, an expert in polymers and additives at Central Michigan University, suggests that studies of toxicity of phosphorus FRs often group very different molecules, often also including phosphorus-containing halogenated FRs, resulting in “muddled conclusions”. Professor Howell considers that more data is needed on complex organophosphorus FRs, whereas much existing data concerns simple alkyl and aryl phosphate esters. He suggests that the toxicity of “more effective” organophosphorus FRs (that is, with a lower level of oxygenation at phosphorus: phosphonates, phosphinates, phosphine oxides) “exhibit no or minimal toxicity …” and that compounds with low levels of phosphorus oxygenation show little toxicity (e.g. DOPO). He suggests that to support future FR design and use, the relationships between oxygenation levels of phosphorus and toxicity, and between structure (size of molecule, branching) and toxicity should be investigated, including investigating whether toxicity can be related to thermal degradation pathways which have been widely studied to inform fire behaviour.
“Toxicity of organophosphorus flame retardants”, J. Fire Sciences, vol. 41, issue 3, 2023 https://doi.org/10.1177/07349041231161493