Airborne microbial contamination of dental units

Occupational risk of dental personnel to microbial airborne contamination has been demonstrated through the increased prevalence of respiratory infections. The American Dental Association has suggested stringent protection for infectious agents present in dental aerosols. Materials and Occupational exposure of dentists to airborne microbial and mycological contamination in various locations of a dental school was monitored by sampling of air in close vicinity of their breathing zone. This sampler drew air at a flow rate of 10 liters/minute and for a 2-hour period and blew it at a high speed through a narrow slit over a solid nutrient agar plate. Immediately after sampling, the plates were placed in an incubator and incubated aerobically for 2 days at 37C. The total bacterial counts in the air of dental surgery rooms and in non-surgery rooms without direct involvements with dental operations were in the range of 120-280 cfu/m3 and 49-128 cfu/m3 respectively. Pathogenic Streptococcus haemolyticus and opportunistic Staphylococcus species were found in some locations of dental surgery rooms. There are no standards for acceptable levels of indoor air contamination with pathogenic microorganisms and since pathogenic Streptococcus haemolyticus and opportunistic Staphylococcus species were found in some areas of the dental school, the need for management of possible risk of infective hazards is recognized

new sampler and analysis method for BTEX in ambient air

Benzene, toluene, ethylbenzene and xylene [BTEX] compounds are components of motor vehicle fuel. BTEX are released from exhausts of vehicles and also evaporation from the fuel tank, carburetor and crank case of engines. BTEX are dangerous chemicals that participate in photochemical reactions and produce secondary air pollutants such as ozone, peroxyacethyl nitrate, free radicals and nitrogen oxides. BTEX in ambient air of metropolitan areas has been the subject of concern in many studies through elaborate "Environmental Protection Agency" [EPA] method. Level of BTEX in the ambient air of major Iranian cities, has not been measured in concentration range of part per billion [ppbv] due to the inadequate sensitivity of available gas chromatography systems. The aim of this study was to improve the sensitivity of gas chromatography by using a special sampler and thermal desorber [Micro-Packed Injector]. Our sampler consisted of a 5-centimeter stainless steel tube one millimeter in diameter packed with carbopacked B heat-conditioned samplers utilized for sampling atmospheric BTEX. It was subsequently injected to a custom-made thermal desorber [225C] which was assembled onto the injection port of a gas chromatography device for analysis. BTEX standard atmospheres were analyzed with a gas chromatograph flame ionization detector [GC-FID] with linear range detection of 27.5-275ppb, 23.1-223.6ppb, 20-320-ppb, and 20-320ppb respectively. The Micro-Packed Injector [MPI] installed on ordinary GC-FID improved linear range detection of BTEX from previous ppm detection to ppb range