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The dangers of “forever chemicals” to firefighters

Wednesday 5 May 2021

The IB covers halogenoalkanes at both SL and HL in Topic 10 Halogenoalkanes & benzene but restricts the coverage to chloro-, bromo-and iodoalkanes. This is because the C−F bond (492 kJ mol−1) is so much stronger than the C−Cl, C−Br and C−I  bonds (324, 285 and 228 kJ mol−1 respectively) making fluoroalkanes very unreactive. Students are generally aware of this as it is one of the main reasons why poly(tetrafluoroethene), also known as PTFE or Teflon, is so inert and used in ‘non-stick’ cookware. The fact that fluoroalkanes are very inert makes them excellent fire extinguishers although their use is banned in many situations as those that also contain C−Cl or C−Br bonds (e.g. bromochorodifluoromethane, CBrClF2, known as Halon 1211) cause depletion of the ozone layer (see Incorporating IM, TOK, Utilization etc. Topics 10 & 20).

Polyfluoroalky and perfluoroalkyl substances are collectively known as PFAS. Perfluoroalkyls only contain fluorine as the halogen bonded to carbon atoms whereas polyfluoroalkyls may also contain other halogens as well as many fluorine atoms. PFAS are used in many everyday items such as carpets and electronics and accumulate both in the environment and in humans as they are so unreactive. They are associated with several major health conditions such as cardiovascular disease and there are increasing links to certain types of cancer both of which are major causes of in-service death of firefighters. More than 95% of the population of the US contain PFAS in their body to some extent but a recent study by scientists from Rutgers University has shown that volunteer firefighters contain over 80% more on average than the general population of two PFAS in particular - perfluorododecanoic acid and perfluorodecanoic acid.

PFAS are present in fire suppression foam and in the protective clothing that firefighters wear. Generally the longer firefighters have been in the fire service the higher their level of PFAS due to their greater exposure. It seems clear that as well as protecting firefighters from all the physical dangers associated with fire fighting more thought needs to be given to reducing their exposure to PFAS.


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