Interior and exterior measurements of surface loading rates for settled surface dust in domestic houses and the content of three metals -lead (Pb), cadmium (Cd) and nickel (Ni) -were conducted weekly during the autumn of 2007 in an urban area of Giza, Egypt. Surface mass concentrations of the metals were also calculated. Results revealed that the interior and exterior surface loading rates averaged 1.58 and 8.18 g m À2 per week, respectively. The interior surface mass concentrations of Pb, Cd, and Ni averaged respectively 311.18, 33.09 and 53.51 mg g À1 , and their interior surface loading rates averaged 533.17, 54.78 and 87.84 mg m À2 per week, respectively. The interior surface loading rates of dust were higher at the side streets than at main streets although the interior surface mass concentrations and loading rates of the metals were higher at the main streets than at side streets. Levels were higher in older homes and smoking homes than in new homes and non-smoking homes. Surface Pb per area in all homes exceeded the US EPA and US HUD guidelines (40 mg ft À2 ) of interior floor Pb dust wipe. Significant positive correlation coefficients were found between interior surface loading rates of metals and dust; among surface loading rates of metals; and among metals' surface mass concentration.

The aim of the present study was to investigate the seasonal distributions and weekdays/weekends differences in ambient aerosols and their elemental contents in the atmosphere of the 15 May City, Egypt. Aerosol samples were collected from March 2009 to February 2010. The concentrations of 14 elements including Na, Mg, Ca, K, Al, Fe, Mn, Co, Cu, Zn, Ni, Cd, Pb and Cr were measured by Atomic Absorption Spectrophotometry (AAS). The mean aerosols concentrations were 290 µg/m 3 (spring), 250 µg/m 3 (summer), 330 µg/m 3 (autumn) and 400 µg/m 3 (winter). The measured elements showed a strong seasonal variation; with the highest concentrations in winter and the lowest in summer. Na, Mg, Ca, K, Al and Fe were the dominant elements, followed by Mn, Cu, Zn, Ni and Pb. The minimum concentrations were noted for Co, Cd and Cr. The dominant elements in aerosol represented 94%, 94.51%, 94.61% and 94.28% from the total measured elements and 5.08%, 5.74%, 6.11% and 5.44% from aerosol mass during winter, spring, summer and autumn, respectively. The aerosols concentrations on weekends were reduced by 31.25% in the winter and 15.2% in the summer. The concentrations of the measured elements were higher on weekdays than weekends. The weekday/weekend concentration ratios were 1.69 and 1.38 for total measured elements during winter and summer, respectively. The mean Ni and Cd levels were higher than the proposed WHO, USEPA and the European Community standards. Significant positive correlations were found between the concentrations of aerosols, Mg, Ca, K, Al, Fe, Mn, Co, Zn and Cr. The enrichment factors (EFs) and the non-crustal fractions of all elements indicated that Na, Mg, Ca, K, Fe and Mn originate mainly from soil sources, whereas Co, Cu, Zn, Ni, Cd, Pb and Cr are mostly emitted in the atmosphere of 15 May City from anthropogenic sources.

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Greater Cairo (Egypt) is a megalopolis where the studies of the air pollution events are of extremely high relevance, for the geographical-climatological aspects, the anthropogenic emissions and the health impact. While preliminary studies on the particulate matter (PM) chemical composition in Greater Cairo have been performed, no data are yet available on the PM’s toxicity. In this work, the in vitro toxicity of the fine PM (PM2.5) sampled in an urban area of Greater Cairo during 2017–2018 was studied. The PM2.5 samples collected during spring, summer, autumn and winter were preliminary characterized to determine the concentrations of ionic species, elements and organic PM (Polycyclic Aromatic Hydrocarbons, PAHs). After particle extraction from filters, the cytotoxic and pro-inflammatory effects were evaluated in human lung A549 cells. The results showed that particles collected during the colder seasons mainly induced the xenobiotic metabolizing system and the consequent antioxidant and pro-inflammatory cytokine release responses. Biological events positively correlated to PAHs and metals representative of a combustion-derived pollution. PM2.5 from the warmer seasons displayed a direct effect on cell cycle progression, suggesting possible genotoxic effects. In conclusion, a correlation between the biological effects and PM2.5 physico-chemical properties in the area of study might be useful for planning future strategies aiming to improve air quality and lower health hazards.