Firefighter health 10 μg m-3 of PM10 (particulates with size of 10
µm) and smaller particles. This occurs when the air is still over large cities. Globally, particulates from fire are estimated to kill around 3m per year, mostly from primitive heating and cooking fires, particularly in India and China. Different particle size ranges deposit in
different zones within the respiratory tract. The smallest particles (<0.5 μm) penetrate into the lung interstitium (between the alveolar surface and the blood capillaries), where they have been shown to be particularly dangerous, causing interstitial and luminal oedema. They can also cross the air blood barrier
and enter the bloodstream, triggering dangerous immune responses from the white blood cells – including polymer fume fever – and increased platelet stickiness leading to heart attacks; or in the longer term cause oedema (flooding of the lung) and ultimately death. Many toxicants including molecular PAHs adsorb onto carbonaceous particles and therefore travel deep into the lung, rather than being trapped further up. In addition to VOCs, PAHs and particulates
emitted in most unwanted fires, other toxicants are dependent on the presence of hetero- elements, such as nitrogen or halogens in the fuel.
Isocyanates Potent respiratory sensitisers, isocyanates trigger asthma and sometimes death after a single exposure. They have been commonly identified in fire effluents from burning nitrogen
FOCUS
containing fuel, and are widely used in the manufacture of polyurethanes; as foams in soft furniture and building insulation; as solids for resilient elastomers; and as liquids and sprays for paints. Due to their versatility and wide range of applications, isocyanate containing products can be found in significant quantities throughout the built environment. The two main products in the isocyanate market, with an approximate market share of 90%, are both di-isocyanates: toluene-di-isocyanate (TDI) and diphenylmethane-di-isocyanate (MDI). Inhalation or dermal contact with isocyanates results in respiratory sensitisation; in some cases a single exposure can lead to lifelong asthma.
Halogenated dioxins Polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) are toxic, chemically and thermally stable, and have a tendency for being strongly adsorbed on the surface of particulate matter. PCDD/ Fs formation is favoured at lower temperatures, typical of those of unwanted fires. Numerous studies on animals have also confirmed that some dioxins are carcinogenic and/or mutagenic. Dioxins are highly toxic even at low concentrations (the safe level in food is less than 1 ng per day). Fire effluents and residues are typically oily and sooty. Quantification of dioxins at such low concentrations requires careful clean up prior to analysis, which is expensive and time consuming. For this reason, there is little data on the distribution and quantities of dioxins generated in unwanted fires. General awareness of
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