The Hazelwood coal mine fire that has been burning in Victoria’s Latrobe Valley since February 9 is raising major public health issues for those living in and near the town of Morwell.
In the post below, Fay Johnston and Guy Marks from the Centre for Air quality and health Research and Evaluation* consider the health risks for the people of Morwell and the public health response options, including a targeted evacuation of more vulnerable residents.
Fay Johnston and Guy Marks write:
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We might have survived the summer heatwaves and bushfires around the country but in the Latrobe Valley the environmental health hazards are far from over.
The main problem is the burning Hazelwood open-cut coal mine, which was originally ignited by a grass fire. The mine is located immediately adjacent to the town of Morwell and it is emitting plumes of smoke with high concentrations of particulate matter and, at times, carbon monoxide. A series of health advisories have been issued including a ‘watch and act’ warning from the Country Fire Authority (CFA) on the afternoon of 15 February advising residents to ‘shelter indoors’ because of elevated carbon monoxide readings.
Not surprisingly, the local community has had many questions and concerns. What do we know about pollution from coal fires? Are the inhabitants of Morwell at increased risk of health problems, now or later? Does closing the doors and windows really provide protection for them? As with most public health issues the answers to these questions are both simple and complicated.
What is known about the likely health impacts of exposure to the plume from the coal mine fire?
The simple answer is that even brief severe smoke events are harmful to some people. But who will be affected, in what way, and how severely? Health impacts from pollution are never evenly distributed in a community. Healthy people can usually tolerate episodes of poor air quality quite well. People who are more vulnerable, for example, because of pre-existing heart or lung disease, may experience severe health problems at pollution concentrations that would not worry most people.
The smoke plume from the Hazelwood fire is a complex mixture with a range of ingredients including toxic gases, particles, organic and inorganic chemicals, potentially including heavy metals like mercury. The Victorian Environment Protection Authority have implemented an extensive and systematic monitoring program and so far the specific pollutants of clear concern are not sulphur compounds or heavy metals (often associated with coal burning, and often the focus of community concern), but the elevated concentrations of particulate matter and carbon monoxide.
While there do not appear to be any direct studies of the health impacts of smoke from coal mine fires, there is a wealth of information about particulate air pollution, carbon monoxide, and severe smoke events from bushfires, forest and peat fires.
In large populations, such as Sydney or Melbourne, exposure to high levels of particulates from bushfire smoke for periods ranging from days to weeks have been associated with statistically significant increases in rates of death and out-of-hospital cardiac arrest as well as admission to hospital and flare-ups (“exacerbations”) of chronic respiratory diseases (including asthma and COPD).
In smaller populations, the increased death rate may not be detectable by usual statistical methods. However, changes in more sensitive indicators, such as reports of cough or breathlessness, reported exacerbations of respiratory diseases would certainly be expected if pollutant concentrations were high enough. In parts of Morwell the exposure to elevated concentrations of particulate matter has been unusually severe and protracted. Hence, adverse health effects would be expected in some, more vulnerable, members of the population.
Carbon monoxide (CO) exposure poses a range of challenges as it has a direct impact on the oxygen carrying capacity of the blood. Exposure to toxic levels of CO causes brain and heart problems. The risk of adverse effects of CO exposure relates to both the concentration and the duration of exposure. Elevated concentrations of CO in the outdoor environment that are present for a long enough period to cause harm are extremely unusual as the gas tends to dissipate rapidly. So far the measured concentrations in Morwell have remained far below those known to be uniformly dangerous to all people. However, concentrations that exceed World Health Organisation (WHO) guidelines have been reported and these pose some risk to vulnerable individuals, particularly those with pre-existing heart disease.
One of the major problems in predicting the risk of adverse health effects from particulate and CO exposure in Morwell is the uncertainty about the duration of exposure. Coal mine fires are notoriously difficult to put out and many have been burning around the world for decades. Exposure that may have little impact over period of hours or days, may have more serious, and unpredictable, effects if extended over a period of weeks or even months.
What is the best way to protect the community?
One option is to advise people to “shelter indoors”, that is to stay indoors with the doors and windows closed. However, even with all doors and windows closed, many older Australian homes are poorly sealed and the extent of protection from a non-reactive gas such as carbon monoxide is likely to be very limited. Particulate matter will also equilibrate with outside concentrations over a few hours, albeit a bit more slowly than gases. So for ongoing exposures sheltering indoors is not likely to be especially useful.
Cloth or paper masks will not provide protection against anything other than large contaminants in the air like dust and ash. Specialised P2 masks are designed to filter particles and work well when there is an air tight seal between the face and the mask. There are some practical issues associated with their use. It is difficult to achieve the required seal, especially for children, and it can make breathing harder work. To be effective the masks need to be worn continually. In circumstances where the pollution episode is protracted, this includes indoors and through the night if the indoor air is not otherwise being filtered. Importantly, P2 masks do not protect against gases like carbon monoxide.
In a recent review of public health interventions for severe fire smoke exposures, the only two options with evidence for effectiveness in reducing exposure were moving people to a clean air environment or using indoor air filters.
However, it should be noted that, although good quality air filters will reduce exposure to particulates, they will have no impact on exposure to gases, such as CO. Hence, as long as prolonged exposure to elevated concentrations of CO remains part of the hazard in this event, the only effective protective option is moving vulnerable people to a clean air environment.
The uncertainty about the duration of the fire, and the consequent exposure of people in Morwell to extremely high concentrations of particulates and elevated CO, also complicates the decision about how best to protect the community. Relocating hundreds of people, possibly for months, is a major decision leading to enormous costs and disruption to the lives of those who leave their homes. On the other hand, as noted above, the longer the exposure lasts, the greater are risks of adverse health impacts. Targeted evacuation of those who live in highly exposed areas and those who are more vulnerable because of pregnancy, age, or pre-existing illnesses including anaemia, heart and lung disease must be considered as a possible response.
What can we learn from this event?
Undoubtedly emergency services and mine management experts are learning many important lessons about prevention and mitigation of future similar events. There is almost certainly important knowledge to be gained about the health impacts too. Given the rarity of coal mine fires, particularly those involving brown coal, and the dearth of current evidence specific to this hazard, it is important that health outcomes in the exposed population are monitored to inform the public health response to future similar events, in Victoria and elsewhere.
*The Centre for Air quality and health Research and evaluation (CAR) (www.car-cre.org.au) is NHMRC funded Centre for Research Excellence. It is a collaboration among senior researchers in the fields of epidemiology, toxicology, air physics and chemistry, biostatistics and clinical respiratory medicine based at universities in NSW, Tasmania, Queensland, and Victoria.