Nanotechnology is a scientific and engineering technology conducted at the nano-scale, such as in the fields of compound fabric manufacturing, food processing, agricultural processing, and engineering, as well as in medical and medicinal applications. In recent decade, nanomaterial applications for antimicrobial works have of prime interest of by many researchers. Available reports show that some of the metal oxide nanoparticles (NPs) including Al2O3, TiO2, ZnO, CuO, Co3O4, In2O3, MgO, SiO2, ZrO2, Cr2O3, Ni2O3, Mn2O3, CoO, and Nickel oxide have toxicity toward several microorganisms and they could successfully kill numerous bacteria. Based on our literature review there are some effective factors that can influence the ability of nanomaterials in reducing or killing the cells, and there are mechanisms for nanomaterial against bacteria, which are briefly listed as follows: surface charge of the metal nanomaterial, shape, type and material, concentration of nanomaterial, dispersion and contact of nanomaterial to the bacterial cell, presence of active oxygen, liberation of antimicrobial ions, medium components and pH, physicochemical properties, specific surface-area-to-volume ratios, size, role of growth rate, role of biofilm formation, cell wall of bacteria, and effect of UV illumination. It can be considered that in the use of nanomaterials as antimicrobial agents, consideration of many factors remain principal. Antibacterial resistance to common chemical antibacterial agents can be due to long production-consumption cycle, thereby reducing their efficiency, and use of poor quality or fake medicines in undeveloped and developing countries. NPs as antimicrobial agents have become an emerging approach against this challenge, which can establish an effective nanostructure to deliver the antimicrobial agents for targeting the bacterial community efficiently. In addition, they are so potent that microbial pathogens cannot develop resistance to wards them. On the other hand, most of the metal oxide NPs have no toxicity toward humans at effective concentrations used to kill bacterial cells, which thus becomes an advantage for using them in a full scale. However, over the present decade, several studies have suggested that NPs are excellent antibacterial agents, at least at the research level.

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Background: Some human diseases such as tuberculosis, Legionnaires' disease and different forms of bacterial pneumonia, coccidioidomycosis, influenza, measles, and gastrointestinal illnesses are the result of exposure to bioaerosols. In addition, they are associated with some noninfectious airway diseases, such as allergies and asthma. Objectives: In the education hospitals of Hamedan University of medical sciences, there were no previous qualitative and quantitative studies of bioaerosols in the air of wards, so in this study the quality and quantity of bioaerosols in hospital ward's air was investigated to establish a reference for future studies or measures. Materials and Methods:In this cross sectional research, 30 wards in five educational hospitals of Hamadan city were studied. More than 180 air samples were collected from the hospitals. The samples were transferred to blood agar and Sabouraud medium and cultivated immediately. Type and number of colonies were determined in the laboratory. Bioaerosol concentrations were calculated in terms of cfu/ m 3 . After bioaerosols isolation, the isolates were identified by morphology of colony, Gram staining and by standard biochemical tests as required for bacterial or fungal bioaerosols. The SPSS software was used for data management. ANOVA and t-test statistical analyses were also used. Results:As the results demonstrated, highest and lowest averages of bioaerosol density were obtained from Shahid Beheshti and Fatemieh Hospitals (36.18 cfu/m 3 Vs. 24.03 cfu/m 3 ), respectively. Highest and lowest concentrations of bioaerosols were found in Women1 and operating room wards of Fatemiyeh Hospital, respectively (54.4cfu/m 3 VS. 13.3cfu/m 3 ). It appears that there had been no significant correlation between concentration of bioaerosols in the hospitals and available guideline values (P = 0.3). The highest fungal populations were Penicelium spp. (32.06%), Cladosporium spp. (20.5%), Aspergillus fumigatus (14.61%) and A. niger (7.43%), respectively. The highest bacterial population was coagulase-negative staphylococci (32.49%), Bacillus spp. (14.74%), Micrococcus spp. (13.68%) and Staphylococcus aureus (11.34%), respectively. Conclusions: Quantitative bioaerosols concentration in the air of some hospitals was more than the available guideline i.e. 30 cfu/m 3 . Bioaerosol density of all surveyed hospitals can relate to patients presence in wards and their visitors, incorrect ventilation, and probably inefficient disinfection. Most surveyed hospitals have no air treatment systems thus to reduce bioaerosol concentration, standard ventilation systems should designed and utilized.

The heavy metal (Pb, Cd, Cr, and Ni) content of a fish species consumed by the Sistan population and its associated health risk factors were investigated. The mean concentrations of Pb, Cd, and Cr were slightly higher than the standard levels. The Ni content of fish was below the maximum guideline proposed by the US Food and Drug Administration (USFDA). The average estimated weekly intake was significantly below the provisional tolerable intake based on the FAO and WHO standards for all studied metals. The target hazard quotients (THQ) of all metals were below 1, showing an absence of health hazard for the population of Sistan. The combined target hazard quotient for the considered metals was 26.94 × 10. The cancer risk factor for Pb (1.57 × 10) was below the acceptable lifetime carcinogenic risk (10). The results of this study reveal an almost safe level of Pb, Cd, Cr, and Ni contents in the fish consumed by the Sistan population. Graphical abstract ᅟ.

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