Collection efficiency of a personal sampler for microbiological aerosols.

A modified personal impinger (MPI) for sampling airborne microorganisms was tested for collection efficiency with the jet nozzle placed at various positions above and below the liquid surface. The sampler was operated with 10 mL of water and sampling rates between 1.08 and 3.4 L/min. The collection efficiencies for a polydisperse aerosol of diethylhexyl phthalate (DEHP) and monodisperse aerosols of polystyrene latex particles (ULP) were determined with an optical particle counter. The results show that a test aerosol generated from a suspension, such as ULP, gives test results that agree better with theoretical predictions than a polydisperse oil aerosol such as DEHP. The measured aerodynamic 50% cutoff diameters (D50) agreed with those predicted from impaction theory with the jet nozzle 4 mm from the flask bottom. For preservation of viability during sampling of microorganisms, it is common to use impingers with the jet nozzle above the liquid surface. These tests showed that if the MPI is operated with the jet nozzle above the liquid surface, D50 will be displaced toward larger particle sizes because the jet-to-plate distance/jet diameter ratio increases substantially when a soft impaction surface such as the liquid is used. The increased D50 could to some extent be compensated for by increasing the flow rate. An increased flow rate will, however, result in more losses because of aerosol regeneration.

Mutagenicity testing of condensates of smoke from titanium dioxide/hexachloroethane and zinc/hexachloroethane pyrotechnic mixtures.

Condensates of smoke from titanium dioxide/hexachloroethane and zinc/hexachloroethane pyrotechnic mixtures were investigated for their potential to produce genetic damage in the tester strains TA98, TA100, TA1535 and TA1537 of Salmonella typhimurium and in the mouse bone marrow micronucleus assay. Both smoke condensates contained several chlorinated hydrocarbons among which tetrachloroethylene, hexachloroethane, hexachlorobutadiene and hexachlorobenzene were identified by GC/MS. Condensate of smoke from titanium dioxide/hexachloroethane showed a dose-related positive response in the Salmonella assay with strains TA98 and TA100 in the absence of metabolic activation from rat liver S9 fraction. Both smoke condensates were negative in the micronucleus assay but produced a small but significant depression of erythropoietic activity. The results indicate that smoke condensate from titanium dioxide/hexachloroethane mixtures contains unidentified compound(s) that may be considered mutagenic in the Salmonella assay.

A comparative study of the acute inhalation toxicity of smoke from TiO2-hexachloroethane and Zn-hexachloroethane pyrotechnic mixtures.

Rats was exposed to white smoke generated from mixtures of titanium dioxide-hexachloroethane (TiO2-HC) and zinc-hexachloroethane (Zn-HC), respectively, in an inhalation chamber operated in the static mode. The dose was varied by varying the amount of smoke mixture and/or the exposure time. The acute inhalation toxicity of TiO2-HC smoke was much lower than the Zn-HC smoke. Thus, the animals survived exposure to TiO2-HC smoke, even at relatively high smoke concentrations. This smoke was irritating to the animals and minor, acute inflammatory changes were seen in lung tissue. In contrast, Zn-HC smoke was very toxic and caused lethal injuries to the experimental animals, even at relatively low concentrations. Pulmonary injuries were extensive and death was due to blood congestion with pulmonary oedema. Since the TiO2-HC and Zn-HC mixtures form TiCl4 and ZnCl2, respectively, a separate study was performed in which rats were exposed to TiCl4 gas or ZnCl2 aerosol. No animals died from exposure to TiCl4 at concentrations between 370 and 2900 mg/m3 for 10 min. The LC50 of ZnCl2 was found to be around 2000 mg/m3 during a 10-min exposure period. The difference between the two types of smoke is explained by the difference in toxicity between TiCl4 and ZnCl2.