Nitrous oxide exposure and staff fertility

Added: November 2018

Hospital or dental staff that work in areas where nitrous oxide is administered to help relieve patient pain could be at risk of developing fertility problems, according to several studies.

Nitrous oxide is a colourless and odourless gas commonly known as laughing gas. It is a powerful analgesic in sub-anaesthetic concentrations and is most commonly used as a 50:50 mix with oxygen, typically known as Entonox.

Although it is inhaled through a demand valve by the patient, when they exhale, some of the nitrous oxide is released back into the room, putting staff at risk of prolonged exposure where rooms are poorly ventilated.

As a result, the staff most at risk are those that administer Entonox regularly as part of their job, particularly midwives, dentists/dental nurses and hospital staff working in Accident & Emergency, Critical Care, Endoscopy and Paediatrics.

Effects of N2O on female fertility

Several studies carried out into the effects of Nitrous Oxide exposure on female medical staff have shown an increased incidence of abortion and congenital deformities(1).

For example, in one study the abortion rate was found to have increased 1.2-fold amongst 737 pregnant anaesthetists who worked during their first two trimesters (Knill-Jones et al. 1972)

In another study, of 407 pregnancies and 341 births by dental assistants who were exposed for 1-8 h/week to N2O, the abortion rate was shown to have increased 1.75-fold and congenital deformities 1.58-fold (Cohen et al. 1980).

Although, it can be virtually impossible to directly attribute a specific incidence of abortion or congenital deformity to nitrous oxide exposure, it is clear that Nitrous Oxide can have reproductive toxic effects in some circumstances.

This has been further underlined by additional studies on pregnant rats. In one such study, exposure of concentrations of 500000 to 750000 ml/m3 resulted in an increased resorption rate, delayed growth and various skeletal and visceral anomalies.

In fact, even when exposed to much lower concentrations of 500ml/m3 in another study, only 6 out of 12 exposed rats produced young, compared to 12 out of 12 in the control group.

Nitrous Oxide exposure and male fertility

There have also been studies carried out that have shown an increased incidence of abortions or deformities in children where the father, rather than the mother, was exposed to anaesthetics(2). However, other studies have shown that nitrous oxide exposure in well-ventilated operating theatres had no detrimental effect on sperm health (3).

That said, Nitrous Oxide is known to diminish Vitamin B12 levels and a deficiency of this vitamin is associated with reduced sperm count (4) and fertility (5), so there are certainly concerns around men being exposed to N2O.

Protecting staff from N2O exposure

The best way to ensure that your staff are not exposed to hazardous levels of Nitrous Oxide is to carry out workplace exposure monitoring.

This will help you comply with the Control of Substances Hazardous to Health regulations which require you to monitor and record staff exposure to Nitrous Oxide against Workplace Exposure Limits set out by the Health & Safety Commission.

Workplace exposure monitoring can be carried out easily by attaching a personal sampling tube attached to staff clothing near the breathing zone for the duration of a shift. This tube is then analysed and a report produced from the findings.

If hazardous levels of exposure are detected, you can then address the problem and bring exposure levels down to permissible levels.

Of course, in addition to personal sampling, it is also a good idea to carry out good housekeeping on an ongoing basis. This can include keeping Entonox equipment well-maintained to help prevent the risk of leaks and ensuring that any ventilation or scavenging systems are working properly.

For information on Cairn Technology’s personal sampling service for Nitrous Oxide just call 0845 226 0185 and ask for our workplace monitoring team or email them at info@cairntechnology.com

(1)              MAK collection for Occupational Health & Safety, Wiley Online Library: http://onlinelibrary.wiley.com/doi/10.1002/3527600418.mb1002497e0009/pdf

(2)              ASA 1974, Askrog and Harvald 1970, Cohen et al. 1975, 1980, Knill-Jones et al. 1975)

(3)              Wyrobek et al. 1981

(4)              Tomaszewski et al. 1963, Watson 1962

(5)              Blair et al. 1968, Sharp and Witts 1962, Smith 196

Donna Bedford`