BackgroundBuilding demolition can lead to emission of dust into the environment. Exposure to silica dust may be considered as an important hazard in these sites. The objectives of this research were to determine the amount of workers' exposure to crystalline silica dust and assess the relative risk of silicosis and the excess lifetime risk of mortality from lung cancer in demolition workers.MethodsFour sites in the Tehran megacity region were selected. Silica dust was collected using the National Institute for Occupational Safety and Health method 7601 and determined spectrophotometrically. The Mannetje et al and Rice et al models were chosen to examine the rate of silicosis-related mortality and the excess lifetime risk of mortality from lung cancer, respectively.ResultsThe amount of demolition workers' exposure was in the range of 0.085–0.185 mg/m3. The range of relative risk of silicosis related mortality was increased from 1 in the workers with the lowest exposure level to 22.64/1,000 in the employees with high exposure level. The range of the excess lifetime risk of mortality from lung cancer was in the range of 32–60/1,000 exposed workers.ConclusionGeometric and arithmetic mean of exposure was higher than threshold limit value for silica dust in all demolition sites. The risk of silicosis mortality for many demolition workers was higher than 1/1,000 (unacceptable level of risk). Estimating the lifetime lung cancer mortality showed a higher risk of mortality from lung cancer in building demolition workers.

Background: The prevalence of HIV is increasing in Iran, so obtaining an estimate of the survival of HIV-infected persons can be helpful to prevent and control this infection. Objectives: This research aimed to use the Bayesian joint model by which identifies factors associated with the survival and determine the relationship between the trend of CD4 + T cell counts and survival time in HIV-infected persons. Methods: In this retrospective cohort study, we collected HIV/AIDS surveillance data from Mashhad's Counseling Center of Behavioral Diseases in the province of Khorasan Razavi, Northeast of Iran, during 1994-2014. Data collection included variables CD4 + T cells count, survival time, and other related factors. We used the Bayesian joint model to estimate the survival time and identify the factors associated with survival time in HIV-infected persons. Results: The study included 260 individuals, of whom 212 (81.54%) were male. The survival sub-model of the joint model identified gender (95% credible interval (CI): 0.486, 3.197) and antiretroviral treatment (95% CI:-1.935,-0.641) as the variables associated with the patients' survival. The longitudinal sub-model, which determined the variables associated with the number of CD4 + T-cells included time (95% CI:-0.934,-0.554), age (95% CI:-0.152,-0.011), and antiretroviral treatment (95% CI:-6.193,-3.505). Conclusions: Using CD4 + T cells as a covariate in the Bayesian joint model, the survival time for HIV-infected persons was estimated more precisely than separate model and it can be inferred that at the beginning of antiretroviral treatment, especially in men and controls, the CD4 + T cell counts can increase the survival time of HIV-infected persons.