Text For Citation: 01 Item/Group: 001 Hazard: CHEMICAL

Section 5(a)(1) of the Occupational Safety and Health Act of 1970: The employer did not furnish employment and a place of employment which were free from recognized hazards that were causing or likely to cause death or serious physical harm to employees in that employees were exposed to THE HAZARD OF OVEREXPOSURE TO NITROUS OXIDE: (a)At the Wylie Dental Office, on or about 01/15/2010: the employer did not furnish a place of employment free from recognized hazards that were causing or likely to cause serious physical harm to employees in that employees performing or assisting in dental procedures where nitrous oxide was administered to patients as an anesthetic gas, were exposed to the waste nitrous oxide gas in levels measured at 91.0 PPM 8-hour TWA and 57.0 PPM 8-hour TWA, exceeding the recommended exposure level (REL) of 25 parts per million (PPM) as an 8-hour time weighted average (TWA). The REL was established by the National Institute of Occupational Safety and Health (NIOSH), U.S. Department of Health and Human Services to protect employees from the harmful health effects of nitrous oxide including reduced fertility, spontaneous abortions, and neurologic, renal, and liver disease. Air monitoring conducted on 01/15/2010 indicated employee exposure to airborne nitrous oxide as listed in the following table: A Dental Assistant adjacent to N2O scavenger, exposed for 163 minutes, with an 8 hour TWA of 91.0 PPM nitrous oxide. This level is approximately four times the REL of 25 PPM. This exposure was derived from one sample collected over the 163 minute sampling period, with a zero increment added for the 317 minutes not sampled. A Dental Assistant in the operatory across hall from N2O scavenger, exposed for 165 minutes, with an 8 hour TWA of 47.4 PPM nitrous oxide. This level is approximately two times the REL of 25 PPM. This exposure was derived from one sample collected over the 165 minute sampling period, with a zero increment for the 315 minutes not sampled. Feasible and effective abatement methods can include, but are not limited to the following: Engineering Controls: 1.Perform additional monitoring of nitrous oxide levels, including monitoring of air from the workers personal breathing zone. 2.Leak test all equipment, including cylinder connections, distribution and recovery (scavenger) lines, seals, etc. Exposure to nitrous oxide and repeated sterilization can degrade rubber and plastic components. 3.If not completed, install a nitrous waste gas scavenger system. 4.Supply scavenging mask in a variety of sizes so that the maskfits correctly over the patients face, forming a comfortable and secure fit. 5.Make sure that the scavenging system exhaust rates (flow rates) are approximately 45 liters per minute (L/min) to minimize nitrous oxide flow rate with a flowmeter that is:- Validated to measure air flow within 5 L/min of actual air flow, -Permanently connected to the scavenging system vacuum line, and -Positioned so that it is always visible to the operator. 6.Vent nitrous oxide from all scavenging pumps to the outside of the building away from any fresh air intakes, windows, or walkways. 7.Increase the air flow into the room(s) or increase the percentage of outside air to allow for more air mixing and further dilution of the anesthetic gas. Maintain a balanced air supply and exhaust system so that nitrous does not contaminate adjacent areas. 8.Consider the use of supplementary local ventilation (such as a vent hood) in conjunction with a scavenging system to reduce nitrous exposures in the operatory. The effectiveness of this type of ventilation may depend on its location with respect to the patient and the airflow rates. Do not work between the patient and the exhaust duct, where contaminated air would be drawn through the workers breathing zone. Work Practice Controls: 1.Do not turn on the nitrous delivery system until: -The vacuum system scavenging unit is operating at a flow rate of at least 45 L/min, and - The scavenging mask is securely over the patient's nose or face. 2.Assure the mask is fastened according to the manufacturers instructions to reduce leakage. 3.Flush the system of nitrous after the procedure by administering oxygen to the patient through the anesthetic equipment for at least 5 minutes before disconnecting the gas delivery system. 4.Encourage the patient to minimize talking and mouth-breathing during dental procedures. Respiratory Protection: If levels can not be maintained below 25 parts per million as an 8 hour time weighted average, and until such time as these modifications are put into place, the employees should be provided with: 1.Wearing air supplied respirators. If respirators are used, the employer must comply with the provisions of the OSHA Respiratory Protection Standard, 29CFR 1910.134. Abatement Disclaimers: 1.The employer is not limited to the abatement methods suggested by OSHA. 2.The abatement methods explained are general, and may not be effective in all cases. 3.The employer is responsible to selecting and carrying out an applicable abatement method. Abatement certification must be submitted for this item.