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Poor air quality is one of the most important environmental problems in many large cities of the world, which can cause a wide range of acute and chronic health effects, including partial physiological disorders and cardiac death due to respiratory and cardiovascular diseases. According to the latest edition of the national standard for air quality, maximum contamination level is 15 μg/m(3) per year and 35 μg/m(3) per day. The aim of this study was to evaluate cardiovascular, respiratory, and total mortality attributed to PM2.5 in the city of Mashhad during 2013. To this end, the Air Q model was used to assess health impacts of PM2.5 and human exposure to it. In this model, the attributable proportion of health outcome, annual number of excess cases of mortality for all causes, and cardiovascular and respiratory diseases were estimated. The results showed that the number of excess cases of mortality for all causes and cardiovascular and respiratory diseases attributable to PM2.5 was 32, 263, and 332 μg/m(3), respectively. Moreover, the annual average of PM2.5 in Mashhad was obtained to be 37.85 μg/m(3). This study demonstrated that a high percentage of mortality resulting from this pollutant could be due to the high average concentration of PM2.5 in the city during 2013. In this case, using the particle control methods, such as optimal use of fuel, management of air quality in urban areas, technical inspection of vehicles, faster development of public transport, and use of industrial technology can be effective in reducing air pollution in cities and turning existing situations into preferred ones.

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Diazinon is an organophosphate compound that inhibits the activity of acetylcholinesterase. Standards of the World Health Organization and Environmental Protection Agency for diazinon concentration in water are 0.1 and 9 × 10−6 mg/L, respectively. The aim of this study was the optimization of diazinon biodegradation from aqueous solutions by Saccharomyces cerevisiae using the response surface methodology (RSM). Harvested cells of S. cerevisiae were locally purchased from the Iranian Research Organization for Science and Technology. To obtain the optimum condition for diazinon biodegradation using RSM, input parameters included the initial concentration of diazinon (0.01–10 mg/L), concentration of S. cerevisiae (0.5–5%), pH (4–10), and retention time (1–30 h). The research study had a central composite design where one of the methods was RSM. According to the results, the observed values of the removal efficiency of diazinon were variable in the range of 23–96. The highest removal rate was obtained as 96% under the initial diazinon concentration of 2.5 mg/L, S. cerevisiae concentration of 3.88%, pH of 5.5, and retention time of 22.75 h. The results displayed that the removal efficiency of diazinon had a direct relationship with the concentration of S. cerevisiae and retention time, and an inverse relationship with pH and the initial concentration of diazinon. We can conclude that S. cerevisiae has the ability to remove diazinon with the lowest cost and a high efficiency.