Abstract—People stay most of the time indoor in humid climatic countries. Since synthetic materials especially plastics occupies our living rooms, indoor-accumulated dust is a health concern. Indoor surface dust samples were collected from living room of households in the city of Muscat, Oman. Samples were analyzed to identify 6 different species of phthalates using gas chromatography/mass spectrometry (GC/MS). Total phthalates concentration ranged from 0.01 to 1864.58 μg/g. Di-n-octyl phthalate (DNOP) was the predominant species contributing to more than 80% of the identified phthalates followed by di-n-butyl phthalate (DnBP) and bis(2-ethylhexyl) phthalate (DEHP). The presence of high concentration of DNOP in surface dust samples probably may reflect the carpet usage in Omani houses. The species of phthalates reported in this study are not comparable to those from studies conducted in other countries. Index Terms—Exposure, muscat, phthalates, surface dust. I. INTRODUCTION Indoor dust harbors chemicals that have been linked to an increased health risk. Chemicals such phthalates are slowly released from household products, flooring, electrical goods, beauty and cleaning products. Phthalates levels in house dust are reported to be generally more concentrated in the outdoor samples. Phthalates or phthalate esters are a group of chemical compounds used in the production of plastics (as a plasticizers), detergents, adhesives, wood finishes, plumbing pipes, lubricants, medical tubing, medical devices, building materials, and vinyl flooring. Phthalates are hormone-disrupting chemicals that interfere with the production of the male sex hormone, testosterone, which is necessary for proper development and function of the male reproductive organs. The National Academy of Sciences (NAS) [1] concluded that prenatal exposure to seven phthalates caused adverse effects on male reproductive development in animals, causing “phthalate syndrome” which is similar to human “testicular dysgenesis syndrome”. As per National Human Activity Pattern Survey [2], People spend more than 87% of their time in indoor environments, creating a link between indoor environmental quality and their health. In the present study, phthalates levels of indoor surface dust were evaluated in Omani houses. In Oman, the Manuscript received April 20, 2018; revised July 20, 2018. Fatma Al Touqi is with Wattaya Health Centre, Ministry of Health, Muscat, Oman. Hameed Sulaiman and Hassan Al-Reasi are with Biology Department, Sultan Qaboos University, Muscat, Oman. S. P. Sathish Babu is with Central Analytical and Applied Research Unit, Sultan Qaboos University, Muscat, Oman (e-mail: sathishpandi@gmail.com). climate is generally hot and arid, due to which people stay longer time indoors and hence it is important to assess the indoor environment for better health. II. MATERIALS AND METHODS A. Study Area Muscat Governorate is the largest and capital city of Sultanate of Oman. People prefer to spend most of the time indoor since climate is very hot, arid with long summer and the temperature reaches as high as 49ºC. Surface dust samples from Omani dwellings were collected from three main towns of Muscat Governorate namely A’Seeb, Bousher and Muttrah. B. Method of Collection Dust samples were collected from thirty different houses in Muscat within a period of two months (September and October 2014). Vacuum samples from multi-surface objects (35 cm above the floor level) which includes shelves, cupboards, frames, windowsills, electronic sets and interior material such as wallpaper and the ceiling were collected. The home owners were requested not to vacuum the sampling areas for a period of 1 week before the scheduled sampling. C. Questionnaire A questionnaire was distributed and collected from each sampled house. The main aim is to find out whether there is any relationship between phthalates concentrations in multi surface dusts to the percentage of plastic materials used in the living space. D. Reagents and Standards Phthalates standard mixture was purchased from Supelco (40077-U). It includes dimethyl phthalate (DMP), diethyl phthalate (DEP), di-n-butyl phthalate (DnBP), benzyl butyl phthalate (BBP), bis(2-ethylhexyl) phthalate (DEHP), and di-n-octyl phthalate (DNOP). The concentration for each phthalate was 1000 μg/ml in iso-octane. Different concentrations of the standard were prepared in methanol. High-performance liquid chromatography (HPLC) grade hexane and acetone (Sigma) was employed as extraction solvent with hexane: acetone ratio of 1:1. E. Sample Preparation The vacuum dust samples were collected and stored in an amber colored glass bottles. The collected dust samples were air-dried for 24 hrs under a fume hood. Particles other than fine dust like hair, insects, food scrapes, scrape paper and large particles were manually removed by wearing a powder Concentrations of Selected Phthalate Esters in Surface Dust in Omani Houses Fatma Al Touqi, Hameed Sulaiman, S. P. Sathish Babu, and Hassan Al-Reasi International Journal of Environmental Science and Development, Vol. 9, No. 11, November 2018 345 doi: 10.18178/ijesd.2018.9.11.1127