The pyrolysis products of plastics--problems in defining their toxicity

Particle size-dependent radical generation from wildland fire smoke

Firefighting, along with construction, mining and agriculture, ranks among the most dangerous occupations. In addition, the work environment of firefighters is unlike that of any other occupation, not only because of the obvious physical hazards but also due to the respiratory and systemic health hazards of smoke inhalation resulting from combustion. A significant amount of research has been devoted to studying municipal firefighters; however, these studies may not be useful in wildland firefighter exposures, because the two work environments are so different. Not only are wildland firefighters exposed to different combustion products, but their exposure profiles are different. The combustion products wildland firefighters are exposed to can vary greatly in characteristics due to the type and amount of material being burned, soil conditions, temperature and exposure time. Smoke inhalation is one of the greatest concerns for firefighter health and it has been shown that the smoke consists of a large number of particles. These smoke particles contain intermediates of hydrogen, carbon and oxygen free radicals, which may pose a potential health risk. Our investigation looked into the involvement of free radicals in smoke toxicity and the relationship between particle size and radical generation. Samples were collected in discrete aerodynamic particle sizes from a wildfire in Alaska, preserved and then shipped to our laboratory for analysis. Electron spin resonance was used to measure carbon-centered as well as hydroxyl radicals produced by a Fenton-like reaction with wildfire smoke. Further study of reactive oxygen species was conducted using analysis of cellular H(2)O(2) generation, lipid peroxidation of cellular membranes and DNA damage. Results demonstrate that coarse size-range particles contained more carbon radicals per unit mass than the ultrafine particles; however, the ultrafine particles generated more *OH radicals in the acellular Fenton-like reaction. The ultrafine particles also caused significant increases in H(2)O(2) production by monocytes and lipid peroxidation. All particle sizes showed the ability to cause DNA damage. These results indicate that the radical generation and the damage caused by them is not only a function of surface area but is also influenced by changing chemical and other characteristics due to particle size.

Acute combined effects of HCN and CO, with the use of combustion products from PAN (polyacrylonitrile)--gauze mistures

The combustion product from gauze-PAN (Polyacrylonitrile) micture was used as a material for the evaluation of the combined effects of CO and HCN. Rats and mice were exposed for 30 min. to the combustion products. In mice experiments, the time at which animals turned laterally and were killed, was measured. In experiments with rats, blood COHb and cyanide determinations were made, in addition to the observation of the behavior. Exposure room gas concentrations (O2, CO2, CO, HCN) were determined and temperature in the combustion room was measured during heating. Preliminary experiments with PAN, ranging from 2g to 10g, on mice showed that HCN is responsible for the toxicity of the combustion products from this fiber. In mixture experiments all animals died during exposure. In experiments with mice (8g of total weight of mixed sample), animals in groups with larger proportion of PAN turned over and died earlier and this was explained by higher HCN concentration. In rats experiments (10g), this held true for severe impairment, however, as to the death time, this was not the case. There was a long interval between severe impairment and death in groups with larger proportion of PAN. The larger amount of HCN was produced as temperature rises. A linear relation between COHb concentration and CT (concentration-time) product was shown. There was not a linear relation between blood COHb and cyanide levels. Judging from the blood analyses data, it seemed probable that there is neither an additive nor a synergistic action between CO and HCN with respect to lethal effects.