Cytotoxicity of PM(2.5) and PM(2.5--10) ambient air pollutants assessed by the MTT and the Comet assays.

Ambient air particulate matters are classified into two distinct modes in size distribution, namely the coarse and fine particles. Correlation between high particulate concentration and adverse effects on human populations has long been recognized, however, the toxicology of these adverse effects has not been clarified. In the current report, the cytotoxic effects of the solvent-extractable organic compounds (SEOC) from fine particles smaller than 2.5 microm (PM(2.5)) and from coarse particles between 2.5-10 microm (PM(2.5-10)) were studied. Nine 24h consecutive monthly samples were tested to determine the correlation between cytotoxicity and total SEOC in two size fractions of particulate air pollution. Cytotoxicity of SEOC was measured by two micro-scale mammalian cells-based bioassays: the MTT cell proliferation assay, and the Comet assay for the detection of DNA damage. A well-defined mammalian cell line - Rat 6 rodent fibroblast was employed in the study. The SEOC extracts of air particulate matters were sub divided into two equal parts. One part was dissolved in DMSO, the other in KOH/hexane and then conjugated with bovine serum albumin to produce a lipid-soluble fraction for testing. The DMSO fraction would contain mainly the polycyclic aromatic hydrocarbons (PAH), alkanes and alkanols, while the lipid-soluble fraction would be enriched with fatty acids. The results from MTT assay showed that cytotoxicity of the PM(2.5) was much more severe than the PM(2.5-10), suggesting that toxic SEOC were confined to the fine particles. By and large, the DMSO solubles were much more toxic than the lipid solubles. The degree of cytotoxicity of the DMSO soluble samples is positively correlated to the amount of particulates present in the ambient air. For the PM(2.5), the winter samples were significantly more toxic than the summer samples in terms of cell killing, which seemed to be a direct reflection of the total loading of organic matter in the samples. Results from Comet assays showed that SEOC samples of PM(2.5) derived from winter months induced DNA damage at dosages resulting in no obvious cell killing in the MTT assay. Thus, long-term exposure to non-killing dosage of air pollutants may lead to the accumulation of DNA lesions, which may be one of the mechanisms responsible for the chronic adverse health effects of particulate air pollution.

[1]  R. Zoeller,et al.  Evaluating the effects of endocrine disruptors on endocrine function during development. , 1999, Environmental health perspectives.

[2]  N. Manojlovic,et al.  Cytotoxic effects of air pollutants on mammalian cells in vitro. , 1980, Toxicology.

[3]  T. Mosmann Rapid colorimetric assay for cellular growth and survival: application to proliferation and cytotoxicity assays. , 1983, Journal of immunological methods.

[4]  W. Wilson,et al.  Fine particles and coarse particles: concentration relationships relevant to epidemiologic studies. , 1997, Journal of the Air & Waste Management Association.

[5]  B. Brunekreef,et al.  Acute effects of a winter air pollution episode on pulmonary function and respiratory symptoms of children. , 1993, Archives of environmental health.

[6]  J. Schwartz,et al.  Is Daily Mortality Associated Specifically with Fine Particles? , 1996, Journal of the Air & Waste Management Association.

[7]  E. Wynder,et al.  20 – Chemical Analysis and Carcinogenic Bioassays of Organic Particulate Pollutants , 1968 .

[8]  M. Matsui,et al.  Fatty acid modification of C3H 10T 1/2 fibroblast cells: changes in benzo(a)pyrene metabolism and phorbol ester binding. , 1987, Cancer research.

[9]  D. Dockery,et al.  An association between air pollution and mortality in six U.S. cities. , 1993, The New England journal of medicine.

[10]  G. Hatch,et al.  Evidence that exposure of particulate air pollutants to human and rat alveolar macrophages leads to differential oxidative response. , 1997, Biochemical and biophysical research communications.

[11]  M. Green,et al.  The single cell gel electrophoresis assay (comet assay): a European review. , 1993, Mutation research.

[12]  C. Pope,et al.  Respiratory hospital admissions associated with PM10 pollution in Utah, Salt Lake, and Cache Valleys. , 1991, Archives of environmental health.

[13]  J D Hackney,et al.  Controlled exposures of volunteers to respirable carbon and sulfuric acid aerosols. , 1992, Journal of the Air & Waste Management Association.

[14]  M. Zheng,et al.  Characterization of the non-volatile organic compounds in the aerosols of Hong Kong— identification, abundance and origin , 1997 .

[15]  R. Huebner,et al.  Transformation of rat and hamster embryo cells by extracts of city smog. , 1971, Proceedings of the National Academy of Sciences of the United States of America.

[16]  Judith C. Chow,et al.  Temporal and spatial variations of PM2.5 and PM10 aerosol in the Southern California air quality study , 1994 .

[17]  E. Wynder,et al.  Effect of high-risk diets for colon carcinogenesis on intestinal mucosal and bacterial beta-glucuronidase activity in F344 rats. , 1977, Cancer research.

[18]  M. Mehlman,et al.  Health Effects of Gasoline Refueling Vapors and Measured Exposures At Service Stations , 1989, Toxicology and industrial health.

[19]  A. Merrill Lipid modulators of cell function. , 2009, Nutrition reviews.

[20]  Mortality and air pollution: associations persist with continued advances in research methodology. , 1999 .

[21]  C. Monn,et al.  Cytotoxicity and induction of proinflammatory cytokines from human monocytes exposed to fine (PM2.5) and coarse particles (PM10-2.5) in outdoor and indoor air. , 1999, Toxicology and applied pharmacology.

[22]  I. Weinstein,et al.  Oncogene-induced transformation of a rat embryo fibroblast cell line is enhanced by tumor promoters , 1986, Molecular and cellular biology.