The release of mutagens from airborne particles in the presence of physiological fluids.

Airborne particulates collected indoors in residences and outdoors were extracted by soxhlet extraction and sonication with methanol. In a comparative study in which mutagenic activity was evaluated in the Salmonella typhimurium reversion assay both soxhlet extraction and sonication proved to be suitable extraction methods. First, the residue, obtained by sonication of loaded filters with methanol followed by evaporation to dryness (tar), was sonicated with newborn calf serum and lung lavage fluid from pigs. All serum extracts of the tar were mutagenic to Salmonella typhimurium TA98, and contained direct- and indirect-acting mutagens. However, the mutagenic activity recovered by serum was only about half of the total mutagenic activity of the tar. The other part of the mutagenic activity remained in the tar. Lung lavage fluid was only able to remove 5-10% of direct-acting mutagens from the tar of all samples. About 20% of indirect-acting mutagens from indoor air were recovered in lung lavage fluid, while the lung lavage fluid extract from outdoor air did not show indirect mutagenic activity. Second, mutagenic activity recovered by direct sonication of the filters with physiological fluids was comparable with the recovery obtained by sonication of the tar. However, after sonication of the filter with lung lavage fluid hardly any mutagenic activity remained on the filter, whereas after sonication of the tar a clear mutagenic activity was observed in the non-soluble residue.

Organ specific metabolic activation of five extracts of indoor and outdoor particulate matter.

In this study liver and lung homogenates of untreated and Aroclor 1254-pretreated rats (Wistar) and mice (Swiss) were compared for their P-450 content and their capacity to activate extracts of airborne particulate matter, sampled indoors and outdoors. Results show that in addition to liver, lung homogenates of rat (Wistar) and mouse (Swiss) are also able to activate extracts of airborne particulate matter in a comparative way. Uninduced liver and lung homogenates showed only minor differences in activation capacity in the metabolism of airborne particles. In contrast to liver homogenates, Aroclor 1254 pretreatment of test animals did not give strong induction of metabolic activation capacity of lung homogenates. P-450 content was observed in all liver and lung homogenates of mouse and rat and in human lung homogenates. The results obtained in this study suggest that the respiratory tract may be an important site for in vivo bioactivation of respirable particles.

Toxicity of airborne particulate matter to rat alveolar macrophages: A comparative study of five extracts collected indoors and outdoors.

The toxicity of indoor and outdoor air samples to rat alveolar macrophages was determined by studying the phagocytic activity of these cells in vitro. Clean air samples did not affect phagocytosis at concentrations up to 60 m(3)/plate, but polluted outdoor samples caused a dose-dependent inhibition of the phagocytosis at concentrations varying from 6 m(3) to 60 m(3)/plate. Indoor air samples, especially when polluted with wood smoke, affected phagocytosis at concentrations below 2 m(3)/plate.

Contribution of wood stoves and fire places to mutagenic activity of airborne particulate matter inside homes.

Wood combustion produces compounds that are mutagenic in the Salmonella/microsome assay. As combustion products can be emitted in the home and the use of wood as a residential energy source is growing, an impact on human health might be of concern. In this study experiments were carried out to determine the contribution of wood combustion in stoves and fire places to indoor mutagenic activity under normal living conditions. Airborne particles from living rooms which were heated by stoves, or by fire places, and from outdoors were collected simultaneously. In each room two samples were collected during two consecutive weeks: one week the room was heated by central heating, the other week by wood combustion. Sampling took place in a total of 24 homes. Methanol extracts of the samples were tested in the Salmonella/mammalian microsome assay. Results show that mutagenic activity of outdoor air exceeds indoor mutagenicity. At the same time a correlation is found between in- and out-door mutagenicity, both with and without S9. However, a large difference is found between the ratio -S9/+S9 of in- and out-door mutagenic activity. Systematic differences in the ratio -S9/+S9 between control and experimental conditions are not observed. The use of wood stoves caused an increase of indoor mutagenicity in 8 out of 12 homes. It could be concluded that the use of an open fire consistently leads to an increase of mutagenic activity. This increase was caused by wood combustion products.

Mutagenic activity of airborne particles inside and outside homes.

Indoor concentrations of total suspended particles often exceed outdoor concentrations. Although it is known that particulate matter may contain mutagenic compounds and that several sources in the home produce mutagens, virtually no data concerning the mutagenicity of indoor particulate matter are available. In this study, experiments were carried out to determine the contribution of indoor and outdoor sources to the mutagenicity of indoor particles. Using six samplers, particles in kitchens, living rooms, and outdoors were collected simultaneously. Methanol extracts of the material obtained were tested in the Salmonella/microsome assay. An increase in mutagenic activity was shown in the presence of a metabolizing system in all indoor and outdoor samples but one. The data presented suggest that mutagenic components of indoor particulate matter are different from those found in outdoor particles. Indoor samples show a higher mutagenic activity after metabolic activation, while direct mutagenic activity of indoor particles was lower than that of outdoor particles. Furthermore, only indoor samples showed cytotoxic effects. Our findings suggest that, with respect to the mutagenic activity of particulate matter, cigarette smoke is the most important contaminant of indoor air. Kitchen samples also show mutagenic activity, probably as a result of volatilization of cooking products. No contribution of outdoor sources to mutagenicity of indoor particles was observed.