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2.  Occupational Exposure to Nitrous Oxide in Dental Operatories 
Anesthesia Progress  1986;33(2):91-97.
Occupational exposures to nitrous oxide (N20) were measured in numerous dental operatories. In all cases, the National Institute of Occupational Safety and Health (NIOSH) recommended time-weighted average (for one operation) of 25 ppm was exceeded by wide margins (NIOSH considers 50 ppm to be attainable in dental operatories). However, a new risk assessment is necessary to determine appropriate exposure limits. Many of the operatories were not equipped with scavenging systems and none of them used a scavenging device in combination with a local exhaust ventilation system. Scavenging devices and local exhaust ventilation should be used to control nitrous oxide exposures. Leaks in N20 delivery systems, which were found to be commonplace, should also be controlled. Research and development efforts are needed to improve upon the already existing scavenging devices, and provision for local exhaust ventilation needs to be included in the design of dental operatories.
PMCID: PMC2175458  PMID: 3459383
3.  Fluoroacetic Acid Is a Potent and Specific Inhibitor of Reproduction in the Nematode Caenorhabditis elegans 
Journal of Nematology  1993;25(4):573-577.
Fluoroacetic acid is known to lead to inhibition of aconitase and block both the Krebs and glyoxylate cycles. In this study, we discovered it to be a potent and specific inhibitor of reproduction in a bioassay using the nematode Caenorhabditis elegans. Fluoroacetic acid added to the growth medium reduced reproduction in the second generation by 50% at concentrations 3,000 times lower than the concentrations that reduced 24-hour survival by 50%. Four concentrations (2, 4, 8, and 17 mM) of fluoroacetic acid were tested thoroughly. At the two lower concentrations, the survival rates were unaffected, and first-generation reproduction was greatly reduced but not completely eliminated. Survival was reduced at the higher concentrations. Malonate, which inhibits the Krebs cycle, and itaconate, which inhibits the glyoxylate cycle, were tested individually and in combination. The combination did not specifically inhibit reproduction, suggesting another mode of action for fluoroacetic acid. Fluoroacetic acid shows promise as a tool in studies requiring age synchrony.
PMCID: PMC2619424  PMID: 19279811
aconitase; aging; Caenorhabditis elegans; fluoroacetic acid; fluorocitrate; lethality; nematode; reproduction
4.  Control of Nitrous Oxide Exposure in Dental Operatories Using Local Exhaust Ventilation 
Anesthesia Progress  1986;33(5):235-242.
An experimental portable local exhaust ventilation system was installed in three dental operatories where nitrous oxide was used routinely. Standard methods of exhaust ventilation design used in industry to control exposures to toxic airborne substances were applied to the dental operatory setting. The concentration of nitrous oxide in the dentists' breathing zones was measured before and after installation to determine the efficiency of the system in reducing occupational exposures. Results indicate that placement of the exhaust opening and exhaust air flow rate are important in determining the degree of control achieved. After the system had been installed in one operatory, peak exposures declined from over 600 parts per million (ppm) to less than 70 ppm: the time-weighted average exposure was below the NIOSH recommended level of 25 ppm. A permanently installed local exhaust ventilation system modeled after the portable one used in this pilot study may be feasible for most operatories and should not interfere with dental procedures. The results suggest that nitrous oxide exposures can be greatly reduced if dental operatories are equipped with local exhaust ventilation.
PMCID: PMC2177485  PMID: 3465259

Results 1-4 (4)