Journal of American Science 2013;9(6s) http://www.jofamericanscience.org in these materials and make them act differently in operations[10]. Therefore Risk assessment is an 42 Occupational Risk Assessment of Engineered Nanomaterials by Control Banding Method in Chemistry Laboratories Rasoul Yarahmadi 1 , Reza Abbaszadeh Dizaji 2* , Ali Asgar Farshad 3 , Fatemeh Teimuri 4 ,Mohammad soleimani 5 1 Assistant Professor of Occupational Health, Faculty of Health, Tehran University of Medical Sciences, occupational health research center, Tehran, Iran 2* MPH,Faculty of Health, Tehran University of Medical Sciencies,Tehran,Iran,Tel:09141476720, 3 Professor of Occupational Health, Faculty of Health, Tehran University of Medical Sciences, occupational health research center, Tehran, Iran 4 Biotechnology Expert, Faculty of Chemical Engineering Modares University,Tehran, Iran 5 Mohammad soleimani, PhD Student in Environment, Urmia University of medical Sciences, Jahad Ave., Urmia, Iran *Corresponding author: popsreza@yahoo.com Abstract: The field of nanotechnology is one of the fastest growing areas of research and technology and numerous workers currently are potentially exposed to engineered nanomaterials (ENMs) in research and industrial sitting. furthermore. initial studies show that toxicity of ENMs is significantly interrelated with emerging physicochemical characteristics of these materials, and may be adverse affects on human health. Aims: Evaluation of physicochemical properties and toxicology and exposure of employees to determine the level of risk by control banding(CB) method. Methods: This research is a descriptive and cross-sectional study of exposure to ENMs in 20 staff members and students involved in five different activities of production and consumption of ENMs. The level of risk factors was determined by a checklist as qualitative assessment of risk based on CB method. Data analysis was performed using Excel software. Results: The study show that highest level of severity index and probability score of risk factors about the process of identifying functional groups of carbon nanotubes are 60 and 67.5, respectively, while the lowest scores for producing silver nanoparticles are 50, 41.25 out of 100. Conclusions : Application of CB method showed that to reduce risk level of exposed to, ENMs, control measures focus on reducing probability score. Thus, some mechanisms, such as engineering controls, replacing hazardous processes and materials with safer ones, and administrative controls may be offered to reduce amount of generated dust and number of workers exposed to ENMs. [Rasoul Yarahmadi, Reza Abbaszadeh Dizaji, Ali Asgar Farshad, Fatemeh Teimuri, Mohammad soleimani. Occupational Risk Assessment of Engineered Nanomaterials by Control Banding Method in Chemistry Laboratories. J Am Sci 2013;9(6s):42-47]. (ISSN: 1545-1003). http://www.jofamericanscience.org. 5 Key Words: engineered nanomaterials ; occupational Risk Assessment;Control Banding Introduction Nanotechnology is leading to the development in many field, of new materials and devices in many fields that demonstrate nanostructure-dependent properties. and development of new products containing engineered nanomaterials (ENMs), is an emerging multidisciplinary technology that involves the synthesies of molecules in the nanoscale size range. ENMs are materials with structural features having at least one dimension in a size range between one and a hundred nanometers. However, concern has been expressed that these same properties may present unique challenges to addressing potential health impact[1,2,3]. Studies show a significant relationship among toxicity of ENMs and their emerging physicochemical properties (i.e., size and shape, aggregation status, surface coating and solubility, etc). These nano-scale properties bring about new behaviors and lead to chemical and physical changes biological systems, which may inflict undesirable affects on human health[3,4]. Experimental studies in rodents and cell cultures have shown that the toxicity of nanoparticles(NPs) is greater than that of the same mass of larger paticles of similar chemical composition[5]. Studies show that Discrete NPs (35- 37 nm median diameter) that deposit in the nasal region may be able to enter the brain by translocation along the olfactory nerve, as was observed in rates [6]. The researchers reported in an in vitro study that single wall carbon nanotubes (SWCNT) cause dose- response and decrease cellular viability. They also induce oxidative stress in biomarkers and lead to significant increase of peroxide lipid in keratin epithelial cells. The authors revealed that exposure to gross SWCNT can increase pulmonary toxicity in workers exposed to oxidative stress [7,8,9]. At present, numerous workers currently are potentially exposed to ENMs in research and manufacturing