Specifications

frequency of nitrous oxide exposure occurred was associated with reduced fecundability (time

required to get pregnant). They found no association between nitrous oxide exposure and

spontaneous abortion. The main critique of this study was the lack of measured nitrous oxide

exposure.

At this point in the research, no dose and effect relationship has been established concerning the

health effects of nitrous oxide exposure in the work environment.

2.2.4 Control Measures

Control measures recommended to decrease exposure in labour and delivery include: tighter

fitting masks, increasing air flow to the room and educating workers about the scavenging

system and how to fit masks properly. NIOSH recommended in an Alert dated 1994 that if

nitrous oxide levels are above the 25 ppm 8 hr exposure limit then air flow into the room should

be increased or the amount of outside air brought into the room should be increased. It stated

that if these methods do not decrease exposure to below the exposure limit then local ventilation

in conjunction with a scavenging system should be used (NIOSH, 1994). Crouch et al, 2000

recommended that the scavenging system used in labour and delivery should have a minimum

flow of 1.6 cfm. The study stated that the scavenging system and general dilution ventilation

have a large effect on nitrous oxide exposures. One very important point made in the study was

that it is impossible to control the patient who is mouth breathing, talking, crying, etc. and these

are the main ways that nitrous oxide is released into the environment.

Bernow et al., in 1984, looked at using containment as a method of decreasing the nurses

exposure to nitrous oxide in labour and delivery. This involved placing the mother’s head in a

plexiglass enclosure for the duration of the labour and delivery. This enclosure acted as

containment and as an exhaust. With this system in place, levels below the NIOSH

recommended exposure limit of 25 ppm were achieved (8 hr TWA 24 ppm), however, this

system was barbaric and it is not likely to be widely accepted.