Use of Mercury in Dental Silver Amalgam: An Occupational and Environmental Assessment.

The objective of this study was to assess the occupational exposure to mercury in dentistry and associated environmental emission in wastewater of Lahore, Pakistan. A total of ninety-eight blood samples were collected comprising 37 dentists, 31 dental assistants, and 30 controls. Results demonstrate that the dentistry personnel contained significantly higher mean concentration of mercury in their blood samples (dentists: 29.835 µg/L and dental assistants: 22.798 µg/L) compared to that of the controls (3.2769 µg/L). The mean concentration of mercury was found maximum in the blood samples of older age group (62.8 µg/L) in dentists and (44.3 µg/L) in dental assistants. The comparison of mercury concentration among dentists, dental assistants, and controls (pairing based on their ages) revealed that the concentration increased with the age and experience among the dentists and dental assistants. Moreover, the mercury concentration in all the studied dental wastewater samples, collected from twenty-two dental clinics, was found to be exceeding the recommended discharge limit of 0.01 mg/L. Therefore, we recommend that immediate steps must be taken to ensure appropriate preventive measures to avoid mercury vapors in order to prevent potential health hazards to dentistry personnel. Strong regulatory and administrative measures are needed to deal with mercury pollution on emergency basis.

Assessment of dental waste management in a Nigerian tertiary hospital.

This study assessed the practice of disposing of waste from the eight dental clinics of Obafemi Awolowo University Teaching Complex, Ile-Ife, Nigeria. All the cleaners (14) in the hospitals were surveyed through questionnaire. Information obtained from the cleaners included socio-economic characteristics (biodata), personal protection, facilities available for them to work with and job satisfaction. Two soil samples were obtained from the open dump site (0.15 and 0.30 m depth) and two water samples were also collected (at 0.00 and 50.00 m) within the vicinity of the dump site. Both the soil and water samples were taken to the central science laboratory for chemical analyses. Ten (71.4%) of the 14 cleaners were not satisfied with their job. The laboratory findings suggested a very high content of lead, chromium, mercury, cadmium and manganese in both soil and water samples in comparison with the Nigerian Federal Environmental Protection Agency standards. The study concludes that the use of tooth-coloured restorative materials and digital X-ray facility to serve as alternatives to the generation of these wastes is recommended and that farming activities should not be allowed in the area until an audit of the soil and water have been performed.

Cost-effectiveness of removing amalgam from dental wastewater.

Mercury in the form of amalgam is commonly introduced into dental wastewater as a result of amalgam placements and removals. Dental wastewater is primarily discharged to municipal sewers that convey industrial and residential wastewater to publicly owned treatment works (POTWs) for treatment prior to discharge to surface waters. In some localities, the sewage sludge generated by POTWs from the treatment of wastewater is incinerated, resulting in the emission of mercury to the atmosphere. Some of the mercury emitted from the incinerators is deposited locally or regionally and will enter surface waters. An assessment was conducted of the use of mercury in amalgam in California and the discharge of that mercury from dental facilities to surface waters via the effluent from POTWs and air emissions from sewage sludge incinerators (SSIs). The annual use of mercury in amalgam placements conducted in California was estimated to be approximately 2.5 tons. The annual discharge of mercury in the form of amalgam from dental facilities to POTWs as a result of amalgam placements and removals was estimated as approximately one ton. The discharge of mercury to surface waters in California via POTW effluents and SSI emissions was estimated to total approximately 163 pounds. A cost-effectiveness analysis determined that the annual cost to the California dental industry to reduce mercury discharges to surface waters through the use of amalgam separators would range from 130,000 dollars to 280,000 dollars per pound.