Jeff Burgess, qualified physician, and specialist in occupational health of firefighters at the University of Arizona, presented the different stages of firefighting operations, highlighting those such as overhaul (ensuring the fire was completely extinguished) where breathing apparatus was not normally worn.
He compared the effects of different personal protective masks (air purifying respirator (APR) cartridges were much less effective than chemical, biological and radiological and nuclear (CBRN) masks). He noted that studies looking for toxic and carcinogenic substances using epigenetic and micro-RNA markers, provide clear evidence of links between exposure and the various occupational diseases of firefighters: a peak in carcinogenic PAH metabolites was found in urine two hours after firefighter exposure.