18 News& Views Nature Vol. 300 4 November 1982 International Organization for Standard­ Fire deaths and toxic gases ization and the development of separate tests in Germany, France, Japan and from Barbara Chernov Levin Belgium. All these tests provide information on AMoNG the industrialized countries which of Utah7 and suggests the need for an the acute toxicity resulting from the record statistics on fires, the United States animal testing system - conventional inhalation of combustion products, but has the most fires per capita. The rate of chemical techniques would have failed to each test is performed in different labor­ fire death in the United States is almost detect such an unusual toxic product. atory decomposition conditions. The tests twice the international average and is sur­ Moreover, scientists at the National do not address the problem of the total passed only by Canada 1 • In 1979, approxi­ Bureau of Standards have found that car­ toxic hazard which a fire produces or the mately 7,800 people died and another bon monoxide concentrations measured at contribution of a material (or product in its 2 31,000 were reported injured • Direct the LC50 of twelve thermally decomposed actual end use) to that hazard under a 'real dollar loss was greater than $5 billion, but materials were 60-4,400 p.p.m., whereas fire' situation. Nonetheless, some building when indirect costs (meeting fire codes, the LC50 of pure carbon monoxide was code officials and state regulators are installing fire protection systems, support­ 5,000 p.p.m. The LC50 here measures the anxious to evaluate the combustion ing fire departments and insuring property) amount of material necessary to kill 50 per product toxicity of materials and are exam­ are included in this calculation, the annual cent of the rats exposed for 30 min. The ining these test methods with that end in cost of fires in the United States is esti­ death of the rats at less than the LC50 of mind. It is important, however, that the mated at more than $20 billion. pure carbon monoxide indicated that acute toxicity (the harmful effects Large fires receive the most public atten­ additional toxic gases or other factors (for measured by the response of laboratory tion and media coverage; for example, example, heat, lowered oxygen concen­ test animals to a single short exposure to three hotel fires between November 1980 trations) were contributing to the cause of combustion products generated by the and May 1981 were the cause of 119 fire death. Many of the exposed rats also died thermal degradation of materials in speci­ deaths and more than 1,000 injuries. Resi­ during a 14 day post-exposure observation fied conditions) be distinguished from the dential fires, however, continue to be the period, an occurrence which cannot be toxic hazard (the materials's properties and cause of most fire deaths and injuries. directly attributed to carbon monoxide the environmental conditions which Approximately 80 per cent of these fire poisoning. increase the probability that a toxic atmos­ deaths are not due to burns, but are attri­ Some of these thermally decomposed phere will occur and an injury will result). buted to inhalation of toxic smoke and hot materials also produced the potent Since any one fire is a dynamic, changing gases3 • This information has prompted the toxicants hydrogen cyanide and/or hydro­ condition and no two fires are alike, no one fire community, materials manufacturers gen chloride as well as carbon monoxide. test can duplicate all 'real fires'. Typical and building code officials to pose the Chemical analysis has detected many com­ fire degradation modes (smouldering, following questions: do some building bustion products in addition to the fre­ radiant heat, non-flaming and flaming) materials and furnishings produce com­ quently examined toxicants - carbon can be reproduced in the laboratory, how­ bustion products that are much more toxic monoxide, carbon dioxide, hydrogen ever, and materials can be tested in these than others, and how can the occupants of chloride, other halogens, oxides of nitro­ conditions. The resultant laboratory buildings be protected from unnecessary gen and sulphur, and ammonia. Scientists toxicity data and other needed inform­ risk in case of a fire? The answers to these at the Fire Research Station in England ation, such as the projected end use of the questions are not simple and involve the have identified 20 chemical species from product, the quantity of material present, evaluation of the total toxic hazard the thermal decomposition of polyacrylo­ its ignition and combustion properties, generated by a fire. nitrile and 30 combustion products from ventilation conditions, and the density and The potential for generating toxic gas polypropylene5 • Michal et al. have sensory-irritant properties of the smoke, from burning materials has long been identified 71 compounds from the com­ may then be related to the total toxic recognized; for example, in the 1929 bustion of polyethylene and 55 compounds hazard. Many of the investigators involved Cleveland Clinic fire, 123 people were from polypropylene9 • Wood generates at in this area of research are now turning killed by the decomposition products of least as many products10 • The relative their talents towards the more challenging nitrocellulose X-ray film 4 • Only recently, contribution of one or various com­ field of toxic hazard analysis. D however, has the fire research community binations of these combustion products to l. Highlights of Fire in the United States 2nd edn (Federal become acutely aware and concerned animal toxicity is so far unknown and Emergency Management Agency, US Fire Administration, 1981 ). about the problem of the toxicity of would require a major research effort to 2. Preview, Residential Fires in the United States (Federal combustion products and the possibility decipher. Emergency Management Agency, US Fire Administration, 1979). that toxic gases other than carbon mon­ The current awareness of the importance 3. Birky, M.M. eta/. Fire and Materials3, 211 (1979). oxide (still a primary toxicant in fires) may of combustion product toxicity is apparent 4. Gregory, K.L., Malinoski, V.F. & Sharp, C.R. Arch. have an important role. Autopsy data show environ. Hlth 18, 508 (1969). from two recent symposia (Annual Society 5. Woolley, W.D. J. Macromo/ec. Sc/-Chem. A17, 1 (1982). a sample of fire victims with less than lethal of Toxicology meeting, February 1982; 6. Clark County Fire Deporrment Report on the MGM Grand amounts of carbon monoxide in their American Chemical Society national meet­ Hotel in Las Vegas, Nevada. on November 21, 1980. 3 5 6 7. Petajan, J .H. eta/. Science 18'7, 742 (1975). blood • • • Other factors may have been ing, March 1982), and by the newly 8. Levin, B.C. et at. Further Development of a Test Method involved, however, as some of the victims convened combustion product toxicity for the Assessment of the Acute Inhalation Toxicity of had pre-existing heart disease and/ or alco­ Combustion Products (NBSIR 82-2532, 1982). commitees of the US National Fire Pro­ 9. Michal, J., Mitera, J. & Tardon, S. Fire and Materials holic intoxication. tection Association and of the US National I, 160 (1976). Laboratory research studies also suggest LO. Alger, R. in The Mechanisms of Pyrolysis, Oxidation and Institute of Building Sciences. Recently, Burning of Organic Materials (ed. Wall, L.A.) (NBS a role for toxicants other than carbon three different animal-based test methods spec. Pub. 357, Washington DC, 1972). monoxide. A highly toxic bicyclic designed to assess the acute inhalation Erratum phosphate compound produced during the toxicity of combustion products were pro­ In the News and Views article 'Promiscuous thermal decomposition of a laboratory­ posed to the Committee on Fire Standards DNA - chloroplast genes inside plant mito­ formulated rigid flame-retarded polyure­ of the American Society for Testing and chondria' by John Ellis (Nature 299, 678; thane foam was identified by the University Materials for their consideration. World­ 1982), the word 'within' in the sentence 'Most wide concern about the toxicity of com­ polypeptides found in the bioenergetic Barbara Chernov Levin is Head of the Fire organelles are encoded and synthesized within Toxicology Research Center for Fire Research, bustion products is indicated by increased activity in a Subcommittee on Toxic the organelles themselves' should be replaced National Bureau of Standards, Washington, by the word 'outside'. DC20234. Hazards of the Fire Test Committee of the

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