Environ. Sci. Technol. 1996, 30, 3512-3516
Mutagenic Activity of Total and Particle-Sized Fractions of Urban Particulate Matter PIERGIACOMO PAGANO,* TONINO DE ZAIACOMO, ELENA SCARCELLA, STEFANIA BRUNI, AND MASSIMO CALAMOSCA ENEA, Environmental Department, Via Don Fiammelli 2, I-40129 Bologna, Italy
Total or inhalable (PM10) particulate matter is monitored as a quality air criteria. Airborne particles deposit onto the differently sensitive biological tissues of the respiratory tract depending on their size. So it is very important to know the mutagenic activity (index of potential carcinogenicity) of the substances carried onto the diverse sized fractions of urban particulate matter, especially those under 1 µm in diameter. The mutagenicity of total and sized fractions of urban particulate matter of Bologna (Italy), representative of a medium size town surrounded by small and medium industries, was investigated using the plate incorporation test on Salmonella typhimurium. There is no correlation between total and/or coarse particle matter concentration in air and mutagenic activity, the correlation increases as the particle size decreases; moreover, the finer the particulate matter, the greater the mutagenicity is. That is of great concern for health risk estimation. Total or inhalable (PM10) particulate matter is not representative of air quality, at least with regard to the mutagenicity.
Introduction In the urban atmosphere, many pollutants originate from chemical reactions among gases, vapors, and particles, producing a variety of substances (1). Airborne particles act as adsorbers, catalysts, and carriers for such compounds into the human respiratory system (2-5). After particle deposition, chemicals should be bioavailable (6). Extracts from airborne particulate matter collected in urban areas proved carcinogenic, under certain experimental conditions (7-10), and mutagenic (11-14). Recent epidemiological studies confirm the airborne particles as an important health risk factor (15), including tumors (16). In the last few years, both epidemiological (17) and experimental data (18-20) have supported the increased consciousness about health problems caused by fine and ultrafine particles (21). * To whom correspondence should addressed; telephone: ++39 51 6098304; fax: ++39 51 6098131; e-mail address: pagano@ risc990.bologna.enea.it.
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The various regions of the respiratory system collect the inhaled particles depending on physical characteristics, e.g., their size (22, 23). For particles below ≈50 nm in diameter, the physical size seems to be a crucial factor of toxicity (24). Moreover, to fine and ultrafine environmental particles, their huge surface in comparison to their mass allows a great amount of toxic substances associated with them to be carried into the deep lung districts. Several authors (25-29) detected the mutagenic activity of atmospheric particulate matter fractionated in size: the conclusion is that mutagenic compounds are almost exclusively located on particles less than 2.0-3.3 µm (14) in diameter. Sampling was usually performed by highvolume cascade impactors; these devices collect, in a short time, a sufficient amount of material to be assayed for mutagenic activity but do not separate particles below 1 µm in diameter. Fractionation of airborne urban particulate matter down to submicronic level would be desirable for a better estimation of the health risk. The aim of this study was to investigate the mutagenic activity of urban particulate matter sampled in Bologna (Italy). Keeping in mind that, for aerosol particles, the human respiratory system is similar to a “particle-size separator” (30) and it is consequently very important to know the deposition site of inhaled particles, the study was particularly aimed at evaluating the mutagenic activity of fine airborne particles fractions.
Materials and Methods Air particulate material was collected in the period September 1994-March 1995 near a very busy road in Bologna (Italy), a 500 000-inhabitant town in the Padana Plain. The samples were collected in a first floor room, taking air from the external environment (31). Total air particulate matter samples were collected on 47 mm diameter glass fiber filters, by a pump running at a flow rate of 20 L/min, for 16 different periods. Andersen impactors Models MKI and MKII, running at 28.3 L/min flow rate, were used to fractionate particulate matter during seven sampling periods lasting 1 week each. Glass fiber disks or aluminium foil disks, 81 mm diameter, were used as supports for collecting particulate matter. The following size fractions were obtained: (diameter) >3.3 µm; 1.1-3.3 µm; 0.7-1.1 µm; 0.4-0.7 µm; 90 µg/m3) air particulate matter concentrations in relation to the other periods (3.3 and 1.1-3.3 µm particles). The correlation is better for finer particles (R ) 0.71, R ) 0.89 and R ) 0.87, respectively, for 0.7-1.1, 0.4-0.7, and
