Search

This paper reports the characterization of residues collected from air pollution controlling devices (APCDs) at seven large-scale municipal solid wastes (MSW) incineration plants. The amount of lime being sprayed in plants is a function of free CaO content in scrubber residues; a higher free CaO content in scrubber residue causes more leaching of lead. The proper amount of lime in the semi-dry scrubbing system was found to be 5 kg/ton of MSW waste. Under these conditions, both the free CaO content and lead leaching became extremely low in scrubber residue.

Epidemiological evidence suggests that chewing betel quid and smoking have synergistic potential in the development of oral squamous-cell carcinoma in Taiwan. Chewing betel quid produces alkalization of saliva. This study investigated the response of human oral cancer OEC-M1 cells to nicotine in different pH environments (6.5 and 8) by examining its effects on DNA damage as evidenced by single-cell gel electrophoresis. Nicotine (1 and 10 muM) significantly induced DNA strand breakage when cultured at pH 8 for 6 h but did not induce DNA damage at pH 6.5. Nicotine-induced DNA damage was also time dependent. When cells were pretreated with catalase or N-acetylcysteine, a significant reduction in nicotine-induced DNA damage was observed. Flow cytometric analyses showed that the production of 8-oxoguanine was significantly increased following nicotine (10 muM) treatment. Posttreatment of nicotine-damaged DNA by endonuclease III and formamidopyrimidine-DNA glycosylase, recognizing oxidized DNA bases, increased the extent of DNA damage. These results suggest that nicotine-induced DNA strand breakage is pH dependent, and oxidative stress might be involved in nicotine-induced DNA damage. Finally, cigarette smoke condensate (equivalent to 8 muM nicotine) induced significant DNA strand breaks in OEC-M1 cells at pH 8 and correlated with the generation of oxidative DNA damage. Thus, alkaline saliva generated by chewing betel quid plays an important role in cigarette-related nicotine-induced DNA damage, and reactive oxygen species may be involved in generating this DNA damage.

A preliminary survey of an arsenic contaminated site from an abandoned copper smelting facility and feasibility study of using solidification/stabilization (S/S) process to treat the contaminant waste were undertaken. It was found that the waste, located in the three-flue gas discharge tunnels, contained 2-40% arsenic. The pH of the contaminated waste is extremely low (ranging from 1.8 to 3.6). The X-ray diffraction evidence indicates that the arsenic particles present in the flue gas mainly exist as As(III), or As(2)O(3). The total amount of arsenic contaminated waste is estimated to be 700 ton in the studied area. About 50% of the particle sizes are less than 2 mm. Arsenic is easily extracted from wastes with a variety of leaching solutions. In order to meet the arsenic leaching standard of the toxicity characteristic leaching procedure (TCLP), an extremely high cement dosage is required in the S/S process (cement/waste weight ratio>6). The waste with lower particle size having higher specific surface area exhibits somewhat positive effect on the S/S performance. The use of fly ash from municipal waste incinerators, in conjunction with the reduced amount of cement, is able to meet the TCLP arsenic and lead standards. The use of lime alone could meet the TCLP arsenic standard, but lead leaching concentrations exceeded leaching Pb standard. The results of semi-dynamic leaching tests of some solidified samples indicate higher accumulated arsenic leaching concentrations after only a few leachant renewals.