Development and application of the Ames test using a direct-exposure module: The assessment of mutagenicity of incense and sidestream cigarette smoke.

We had previously developed an improved Ames module to directly determine the mutagenicity of gaseous formaldehyde (HCHO) and toluene without liquid extraction. This study further evaluated the suitability and sensitivity of this module on whole and real polluted air samples. For this, two common brands of stick incense (A and B) and cigarettes (A and B) were harvested, and various types of incense smoke (IS) and sidestream cigarette smoke (SCS) samples were generated by lighting 3, 6, 12, 24, 30, or 36 incense sticks, and by lighting 1, 2, or 3 cigarettes, respectively, in an acrylic box. CO2 , CO, total volatile organic compound (TVOC), PM1.0, and HCHO concentrations in the air samples were determined, and all air samples did not partially fit the requirements of the air quality standards. The smoke samples were then directly exposed to TA100 for 10, 20, 30, or 60 min in our exposure module. Exposure to IS (brand A) for 30 to 60 min and exposure to IS (brand B) for 60 min led to statistically (p < 0.05) weak (below the twofold rule) but dose-dependent mutagenic activities either with or without metabolic activation. Furthermore, a short-term exposure (10-60 min) to SCS (brands A and B) displayed statistically significant (p < 0.05) direct-acting, indirect-acting, time- and dose-dependent mutagenic activities. Furthermore, our data also support that the liver S9 enzyme could enhance the mutagenic activities in most IS and SCS samples. This study confirmed that the modified Ames module can be applied to directly detect the mutagenic activities of real polluted air samples.

Assessment of the mutagenicity of two common indoor air pollutants, formaldehyde and toluene.

Traditionally, direct-reading instruments have been used to directly determine the concentrations of indoor air pollutants that may exceed the regulation limits. However, these instruments cannot directly assess the potential health hazards of these pollutants to humans. In this study, we developed and improved a bacterial reverse mutation assay (Ames test) by using a direct gas exposure module to directly determine the mutagenicity of indoor air quality using five tester bacterial strains (TA98, TA100, TA102, TA1535, and TA1537). Thereafter, the module was used to evaluate the effects of exposure time, different concentrations of HCHO or toluene, and mutagenic activities. We found that TA100 was the most sensitive strain and was reverted by relatively lower concentrations of 0.035 ppm HCHO. Furthermore, 50 ppm of toluene exposures caused a significant increase in the number of revertant colonies of TA100 without S9 activation at the 1.5-8-h exposure time intervals. Our findings provide new evidence that gaseous HCHO exposure could display weak but direct, time-dependent, and dose-dependent mutagenic activities. The weak, direct-acting, indirect-acting, and time-dependent mutagen of 50 ppm toluene was also confirmed. Moreover, our improved Ames module and the exposure conditions provided in this study can be further applied to evaluate the mutagenicity of indoor air quality.

Assessment of Cellular Mutagenicity of Americano Coffees from Popular Coffee Chains.

Coffee is a popular beverage worldwide, but coffee beans can be contaminated with carcinogens. The Ames Salmonella mutagenicity test is often used for analysis of carcinogens for mutagenicity. However, previous studies have provided controversial data about the direct mutagenicity of coffee beans based on Ames test results. This study was conducted to determine the mutagenicity of popular Americano coffee based on results from the Ames test. Coffee samples without additives that were served by five international coffee chain restaurants were subjected to the analysis using Salmonella Typhimurium tester strains TA98, TA100, and TA1535. The levels of bacterial revertants in samples from coffee chains were lower than the twofold criterion of the control sets, and no significant dose-response effect was observed with or without rat liver enzyme activation. These data indicate that Americano coffees from the selected coffee chains possessed no direct mutagenic activity with or without enzyme activation. These findings suggest a low mutagenic risk from Americano coffees served by the selected coffee chains and support the use of other methods to confirm the nonmutagenicity of coffee products. These results are consistent with most recent epidemiological reports.

Investigating Leggett-Garg inequality for a two level system under decoherence in a non-Markovian dephasing environment.

Leggett-Garg inequalities (LGI) test the correlations of a single system measured at different times. Violation of LGI implies either the absence of a realistic description of the system or the impossibility of measuring the system without disturbing it. We investigate the violation of the Leggett-Garg inequality for a two level system under decoherence in a non-Markovian dephasing environment. We discuss the non-Markovian dynamics of the violation of LGI at zero temperature and also at finite temperature for different structured environments. An enhanced quantum coherence is shown through the violation of Leggett-Garg inequality in the strong non-Markovian regime of the environment.