J. Int. Environmental Application & Science, Vol. 3 (1): 21-28 (2008) 21 Analysis of Mercury in Wastewater of some Dental Clinics in United Arab Emirates Sausan Al Kawas 1 , Imad A. Abu-Yousef 2 , Sofian Kanan 2 , Mohamed El-Kishawi 1 , Abubaker Siddique 3 , Naser Abdo 2 and Amjad Shraim 4,5,∗ 1 Department of Oral and Craniofacial Health Sciences, College of Dentistry, University of Sharjah, Sharjah-UAE, 2 Department of Biology and Chemistry, College of Arts and Sciences, American University of Sharjah, Sharjah-UAE, 3 Zayed Military Hospital, Abu Dhabi, UAE, 4 Chemistry Department, Faculty of Science, Taibah University, Almadina Almunawarah-KSA, 5 National Research Centre for Environmental Toxicology (EnTox), The University of Queensland, 39 Kessels Road, Coopersplains, Brisbane, Queensland 4108, Australia Received January 1, 2008; Accepted January 15, 2008 Abstract: The amount of mercury in the wastewater of three dental clinics from United Arab Emirates over a period of 3 to 17 days was quantified using cold vapour-atomic absorption spectrometry technique. The total Hg concentration in the wastewater of these clinics ranged from 25 to 146 μg d -1 . The Hg concentration in the wastewater samples collected from the outlets of the dental chairs after dental treatments varies depending on the type of dental treatment: the average Hg concentration in the samples of only amalgam restoration is 39 μg per sample (std. dev. 37, range 4-142); for samples with amalgam restoration plus other types of dental treatment is 24 μg per sample (std. dev. 24, range <MDL-77); and for sample with no amalgam restoration is 18 μg per sample (std. dev. 16, range <MDL-33). Keywords: Dental amalgam; mercury; dental wastewater; United Arab Emirates Introduction Amalgam is the most commonly used dental filling material for more than 200 years (Arenholt-Bindslev & Larsen, 1996; Counter & Buchanan, 2004; Horsted-Bindslev, 2004). One of its major components, mercury, is of a particular concern due to its potential adverse effects on humans and the environment (Arenholt Bindslev & Larsen, 1996; Counter & Buchanan, 2004; Horsted-Bindslev, 2004; Hylander & Goodsite, 2006). The estimated annual mercury consumption for dental applications is 3-4 % worldwide (approximately 300 metric tons of mercury) (WHO, 1976; Mukherjee et al., 2004; Vandeven & McGinnis, 2005). Even though the use of amalgam as a restorative material has declined recently, the removal of this material from patient’s teeth and the subsequent discharge of it into the environment will continue as long as existing restorations remain in place and amalgam is continued to be used as a dental filling material. According to recent investigations, dental clinics appear to be responsible about appreciable amount (10-70 %) of the daily mercury burden that has been released into the environment via sewage treatment plants (Drummond et al., 2003; Adegbembo & Watson, 2004). Mercury is known to bioaccumulate in fish and other living organisms and therefore can pose an environmental mercury burden on the entire food chain (Zhou & Wong, 2000; Berzas Nevado et al., 2003; Kennedy, 2003; Hylander & Goodsite, 2006). Among the groups that are directly exposed to mercury are the dentists and their patients, where significant increases in their plasma mercury concentration have been reported compared to those of control groups (Tezel et al., 2001; Harakeha et al., 2002; Jones et al., 2007; Zolfaghari et al., 2007). On the other hand, the public and the environment are indirectly exposed to this element via mercury ∗ Corresponding author: e-mail: ashraim@taibahu.edu.sa, PO Box 344, Fax: +966- 4-8454770