By Isabella Myers, BSc, DIC, MSc, MRSB.

In 2011 the All Party Parliamentary Carbon Monoxide Group (APPCOG) identified a key role for coroners to support the increased detection of carbon monoxide (CO) poisoning in England and Wales. Their report recommended that “The Government should ensure that all coroners’ post-mortems routinely test for carboxyhaemoglobin (COHb) levels”.


By law, where CO is suspected as a cause of death, cases are referred to the coroner, but routine testing for CO exposure is not required. In April 2019 NHS Improvement announced a national program to introduce a new medical examiner role at all hospital trusts to provide independent scrutiny of all deaths.

The new system is currently being rolled-out across England and Wales. Medical examiners are senior medical doctors who are contracted to undertake medical examiner duties, outside of their usual clinical duties. They are trained in the legal and clinical elements of death certification processes.


The purpose of the medical examiner system is to:

  • provide greater safeguards for the public by ensuring proper scrutiny of all non-coronial deaths
  • ensure the appropriate direction of deaths to the coroner
  • provide a better service for the bereaved and an opportunity for them to raise any concerns to a doctor not involved in the care of the deceased
  • improve the quality of death certification
  • improve the quality of mortality data.

The new role will clearly work closely alongside coroners. However, there is an opportunity with this new role to help improve the recording, knowledge and understanding of the impact CO exposure is having on public health: in those with existing chronic conditions, and for those in whom the causal sequence leading to death includes CO exposure.

The CO Issue

The 2011 APPCOG inquiry revealed that there was a significant lack of awareness amongst healthcare professionals regarding exposure to CO at levels that were not immediately fatal. In 2017 the APPCOG medical sub-group (COMED) reinforced this message in its report ‘Carbon Monoxide Poisoning: Saving Lives, Advancing Treatment. A Call for Action Across the Healthcare Sector’.

More recently, concern has been raised that developments in the scientific understanding of CO as an important factor in the cascade of events that result in death has not been fully acknowledged. When scientific understanding is combined with the known difficulties of diagnosis that result in underreporting, and when industry data clearly highlights the risk of exposure in homes, CO must be considered as being a possible underlying cause of, or contributor to death when there is a death in the community. This will allow mortality data to more accurately reflect the impact that CO exposure is having on deaths.


High-level vs low-level

The effects of acute high-level exposure to CO have been recognised for many years. It is widely acknowledged that such exposures do cause death and serious injury to health.

It was originally thought that CO did not cause significant harm to health as the symptoms associated with exposures to lower, non-fatal levels of CO were reversible. The effects of such exposures were considered insignificant on the questionable basis that similar symptoms were produced by many other non-fatal conditions. Tests that prove exposure to CO, can also prove that CO has been removed from the body. This perpetuates the assumption of a lack of harm. This of course is not the case. However, it is important to note that CO remains stable in the blood of the deceased and can therefore be measured accurately at autopsy.

CO poisoning, if suspected and diagnosed in the living, has also been considered as easy to treat, either by the patient breathing fresh air not contaminated with CO, or through the provision of oxygen by a healthcare professional. CO is removed from the body when air not containing CO is breathed in. In some countries other than England, hyperbaric oxygen is used to increase the rate at which CO is removed from the body.

The scientific literature clearly shows that chronic exposure to sub-lethal levels of CO can have effects on health, to the extent where those with underlying disease can find their condition deteriorate at an unexpected rate.

In some cases, the triggering of an acute deterioration of a health condition may cause sudden death. That this might occur in patients with impaired blood supply to the heart and brain seems self-evident.

Scale of the problem

The true scale of the problem is hard to calculate as there are several reasons why an appliance used in the home, workplace, holiday let, caravan, or boat might be the cause of CO poisoning. Industry figures indicate that, due to illegal gas work alone, there are over a million homes in the UK that have appliances that are either unsafe or immediately dangerous. Data on other causes of appliance malfunction such as lack of maintenance, including maintenance of chimneys, and inappropriate use of appliances are hard to gather. This is complicated further when the malfunctioning appliance is leaking CO into a neighbouring property.

Other factors that also contribute to the likelihood of exposure are the amount of time that is spent in the home containing a malfunctioning appliance. Also, when home improvements are undertaken to prevent heat loss but ventilation requirements of the home are not taken into consideration, allowing levels of CO to build up to levels that affect health.

Gas cooker

Legislation and Loopholes

Deaths triggered, aggravated, or contributed to by exposure to what might be considered non-fatal levels of CO exposure, present an issue. They reveal a mismatch with current regulatory and legislative frameworks that encompass safe gas work, the prevention of CO poisoning, and the duties of H M coroners.

The absence of a joined-up approach between accepted and developing scientific knowledge, diagnosis by a healthcare professionals, coronial investigation, and the regulatory and legislative requirements of industry and government departments, creates a loophole that perpetuates illegal gas work. It also makes understanding the extent to which CO exposure is a public health problem difficult. It raises questions regarding ill health associated with CO poisoning and understanding the effects that CO poisoning has on deaths in the community. This is where the role of medical examiner scrutiny of deaths in the community becomes so very important.

The new ME system has potential to save lives

The introduction of the medical examiner system and the changes to the notification of deaths to H M coroners in October 2019, have the potential to facilitate closer consideration of CO as a contributor to, or underlying cause of death. By utilising government and industry regulatory requirements and legislative powers to assist healthcare professionals in their diagnosis of exposure to CO, further fatalities, and the continuation of exposure in the community can be prevented.

Medical examiners and coroners can gather information that will enable relevant government departments and industry to prevent illegal gas work.

If policies are to be effective and legislative requirements upheld, the requirement for a joined up, multi-sectoral approach to provide a framework for tackling the public health burden and avoidable mortality associated with accidental exposure to indoor sources of CO is of greater importance than has, perhaps, been thought.

The introduction of the medical examiner system provides an important opportunity to improve public health in the domestic environment, that previously could not be realised.

The new process - closing the loop

One of the tasks of medical examiners is the scrutiny of death certificates. This allows the detection of error and inappropriate recording on the part of healthcare professionals and should improve the quality of official death statistics. The implementation of such scrutiny is also aimed at ruling out malpractice by healthcare professionals.

Death certificate

The extension of the medical examiner role from the hospital setting to deaths occurring in the community (i.e outside of hospital care), in cases where exposure to CO is suspected, will still be referred to the coroner. However, it is imperative that the consideration of CO exposure at the medical examiner stage includes the consideration of chronic exposure to lower, not immediately fatal levels of CO, alongside the circumstances of death and the individual’s medical history.

An investigation into a death where such levels of CO are considered and suspected, should lead to the identification of for example, poor gas work, malpractice by engineers or unskilled workers undertaking work on domestic fuel powered appliances, and rogue landlords.

This is something that the industry has been working towards for decades. Previously, industry has never had the capability to uncover practices that caused occupants to be exposed to lower levels of exposure to CO; levels that harmed health but that were not fatal. The healthcare, health and safety sector, and government were understandably focused on levels of CO exposure that were fatal. The opportunity has arisen, at last, to close the loop.

By improving knowledge on this known and very silent killer and by being able to provide evidence through better CO data collection is important. Data from death certificates are used to inform practices and policies at a local, regional, national, and global level. Likewise, the analysis of such data informs funding for healthcare development and research. Even where CO is listed as a contributor to death, and the death is not recorded as a CO death in its own right, this information is still of vital importance.

How many lives could be saved, and how much suffering could be prevented through improved recording is currently not known. But it should not be ignored that the information gained from the data that could help in the reduction and ultimately the prevention of accidental death (a death that need not have occurred), from a non-communicable disease should be high on the agenda of any sector with an interest in protecting public health.

Isabella Myers will be presenting the findings of the study looking at the role of the new medical examiner on Thursday 17th Feb at 3pm - to sign up click here.

The Medical Examiner - closing the loop on CO data