2020B Question 08

Discuss the adverse environmental effects of anaesthetic agents in current use

Examiner Report

The question required:

  • A basic knowledge of the terms “greenhouse gas”, “ozone layer” and “global warming”
  • An explanation of how inhalational agents affect the wider environment
  • An explanation of how intravenous agents affect the wider environment

Things that were done particularly well:

  • Ranking of agents by degree of impact
  • Acknowledging the large amount of non-recyclable, solid waste produced
  • Mentioning the adverse effects of N2O upon theatre staff

Things that were done poorly:

  • Accurately differentiating between the basic terms
  • Understanding the effect of propofol on the wider environment

Model Answer


  • Definitions
  • List of agents


Term Detail
Greenhouse Gas

- Substance that absorbs and emits infrared radiation

- e.g. CO2, N2O, methane, ozone

Anthropogenic global warming

- Warming of average temperatures on earth caused by greenhouse emissions arising from human activity

- Many detrimental environmental effects

Ozone layer

- O3 Rich region in the stratosphere

- Absorbs UV-B


Listed in descending order of toxicity

Agent Detail

- Direct AGW: 6 hours at Fi 7% ≈ 1000kmg driving

- 0.02% metabolised; also resistant to environmental breakdown

- Greater impact mostly due to long half life

Nitrous Oxide

- Direct AGW: 6 hours at Fi 50% ≈ 500km driving

- Depletes ozone layer

- Chronic exposure can cause neuropathy, teratogenicity, miscarriage in health care workers due to inactivation of methionine synthetase


- Direct AGW: 6 hours at Fi 3.5% ≈ 50km driving

- ~5% metabolised


- Minimal impact on AGW, even after taking into account syringe driver, manufacture, procurement

- Improperly discarded propofol is toxic to marine life

- Syringes and tubing contribute to medical waste

- Almost 100% metabolised; metabolites excreted in urine

- Environmental effects of metabolites unknown


- Minimal impact

- Can be used as a sole agent

- Minimal effects of ABC

- Hence reduces need for other disposable equipment

Neuraxial/regional local anaesthetics

- i.e. Bupivacaine, ropivacaine, lignocaine

- Minimal direct impact

- Can be performed without sedation or general anaesthesia

- Hence reduces need for other disposable equipment

Last updated 2021-08-23

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