WHAT IS IN SMOKE?
Smoke is made up of a number of different sized particles, water vapour and gases. Larger particles are often visible to the eye and produce the visible haze of smoke. These particles are generally too large to be breathed into the lungs, but can irritate the eyes, nose and throat. Smaller particles cannot be seen and are small enough to be breathed deeply into the lungs. They can cause a range of adverse health effects.6
Smoke produced from the Hazelwood mine fire was similar to, but not exactly the same as smoke produced from a bushfire.
Carbon is the principal element found in coal. Coal includes a number of other elements and compounds, many of which are released when coal combusts. The brown coal found in the Latrobe Valley has a moisture content of approximately 60 per cent, and contains low levels of nitrogen and sulphur, discrete minerals, and minute levels of heavy metals.7 There are no reported health studies on the impacts of brown coal fires on a community in circumstances similar to the Hazelwood mine fire.8 However, the greatest risk to public health from the Hazelwood mine fire was from fine smoke particles.9 In this regard, the risk was similar to risks well known from bushfire smoke.
When evaluating air quality generally, there are three major pollutant categories to consider:
- particulate matter – PM10 and PM2.5
- gases – carbon monoxide, ozone, sulphur dioxide and nitrogen dioxide
- air toxins – volatile organic compounds and metals.10
The Hazelwood mine fire produced pollutants from these three major categories, including the following:
- carbon monoxide
- particulate matter
- sulphur dioxide
- nitrogen dioxide
- volatile organic compounds
- polycyclic aromatic hydrocarbons
- dioxins and furans
- metals (magnesium, manganese, mercury and zinc).11
The Victorian State Environmental Protection Policy (Ambient Air Quality) includes visibility reducing particles as a measure of air quality. The Policy sets the air quality goal and objective for visibility (minimum visual distance) at 20 kilometres for an average of one hour.12 On 16 February 2014, visibility in Morwell was down to between 300 and 500 metres.13
Carbon monoxide is an odourless, tasteless, colourless gas. It is produced as a result of incomplete combustion of coal. Carbon monoxide is an environmental hazard in coal mines and coal-fired power stations. It usually disperses very quickly in open environments with circulating air.14
Carbon monoxide is absorbed through the lungs. When breathed in, it reduces the ability of blood to carry oxygen around the body tissues and vital organs. Carbon monoxide combines with haemoglobin in the blood to form carboxyhaemoglobin. Carboxyhaemoglobin reduces the capacity of the blood to carry oxygen. The short-term effects of exposure to carbon monoxide are summarised in Figure 4.1.
Figure 4.1 Short-term effects of carbon monoxide15
|35 ppm (0.0035%)||Headaches and dizziness within 6 to 8 hours of constant exposure|
|100 ppm (0.01%)||Slight headache within 2 to 3 hours of exposure|
|200 ppm (0.02%)||Slight headache within 2 to 3 hours of exposure: loss of judgement|
|400 ppm (0.04%)||Frontal headache within 1 to 2 hours of exposure|
|800 ppm (0.08%)||Dizziness, nausea, and convulsions within 45 minutes of exposure: insensible within 2 hours|
|1,600 ppm (0.16%)||Headache, tachycardia, dizziness, and nausea within 20 minutes of exposure; death in less than 2 hours of exposure|
|3,200 ppm (0.32%)||Headache, dizziness and nausea within 5 to 10 minutes of exposure. Death within
30 minutes of exposure
|6,400 ppm (0.64%)||Headache and dizziness in 1 to 2 minutes of exposure. Convulsions, respiratory arrest, and death in less than 20 minutes|
|12,800 ppm (1.28%)||Unconsciousness after 2 to 3 breaths. Death in less than 3 minutes of exposure|
In addition to the short-term effects listed above, Professor Campbell advised the Board that increased exposure to carbon monoxide can lead to long-term cardiac and neurological abnormalities, and potentially to foetal injury as a result of hypoxia in the womb.16
Given its toxic nature at high levels, the potential short-term adverse health effects of carbon monoxide are usually the immediate health focus when increased levels are observed.
Particulate matter is also known as particle pollution or particles. Particulate matter is a complex mixture of very small particles and liquid droplets that can combine to make dust, soot and smoke.17 Particulate matter occurs both naturally (for example, it is found in dust storms and even sea spray) as well as through human-related activities, such as wood burning, vehicle emissions and industrial processes. Particulate matter primarily consists of carbon, but also includes transition elements and hydrocarbons.18 The most important chemical constituents of particulate matter are sulphate, nitrate, ammonium, other organic ions (sodium, potassium, calcium, magnesium and chloride), organic chemicals, metals, and soil or dust particles.19
Particulate matter is grouped into two broad categories:
- PM10 – these particles are equal to or smaller than 10 micrometres in diameter. They are inhalable coarse particles such as those found near roadways, farming operations, mining operations, and in dust storms.
- PM2.5 – these are very fine particles equal to or smaller than 2.5 micrometres in diameter. They are found in smoke and haze. The source of these particles is primarily emissions from coal mines or forest fires, or from other combustion processes, such as those that occur in petrol or diesel vehicles, and wood burning.20
Figure 4.2 shows just how small both PM10 and PM2.5 are compared to a human hair and grains of fine beach sand.
Figure 4.2 PM10 and PM2.5 size in comparison to a human hair and fine beach sand21
Professor Campbell told the Board that once inhaled particulate matter can affect the heart and lungs, and cause adverse health effects.22 He advised that coarse particles (PM10) can settle in the bronchi and lungs and cause health problems, but fine particles (PM2.5) have demonstrated the greatest impact on health. Due to their small size PM2.5 can travel deep into the lungs where they can trigger inflammation or deposit potentially cancerous substances.23
Potential adverse health effects from exposure to particulate matter include respiratory illnesses (such as asthma and bronchitis), heart disease, reduced lung function, increased respiratory symptoms, adverse birth outcomes, childhood respiratory diseases and premature death.24 The lung cancer risk associated with fine particulate matter is comparable to that faced by non-smokers living with smokers who are exposed to second hand smoke.25
The greater the exposure to particulate matter, the more likely a person will suffer an adverse health effect. There is no guaranteed safe level.26
The predominant short and long-term effects of exposure to PM2.5 are summarised in Figure 4.3.
Figure 4.3 Predominant short and long-term effects of exposure to fine particulate
Sulphur dioxide is one of a group of highly reactive gases known as sulphur oxides. Sulphur dioxide is invisible and has a sharp smell. It is produced through combustion processes, including coal combustion. When coal combusts, sulphur in the coal is turned into sulphur oxides, primarily sulphur dioxide. The environmental effects of sulphur dioxide include acidification of soil and surface water. Sulphur dioxide also contributes to air pollution by creating secondary particulate matter.28
The known potential human health effects of sulphur dioxide include:
- adverse effects on the respiratory system and lung function
- irritation of the eyes, throat and lungs
- inflammation of the respiratory tract causing coughing and mucous secretion
- aggravation of asthma and chronic bronchitis.29
Nitrogen dioxide is one of a group of highly reactive gases known as nitrogen oxides. Nitrogen dioxide has a sharp, acrid like odour. It is produced both naturally and by combustion processes involved in burning fossil fuels like coal, and through vehicle emissions. Nitrogen dioxide contributes to the formation of photochemical smog, which is the haze seen when sunlight falls on a mixture of chemicals in the air. Nitrogen dioxide can also adversely affect the health of water ecosystems.30
The known potential human health effects of nitrogen dioxide include:
- increased hospital admissions for respiratory disease
- decreased lung function
- cardiovascular disease
- increased respiratory problems (children and the elderly are particularly susceptible).
People with asthma are often sensitive to nitrogen dioxide.31
VOLATILE ORGANIC COMPOUNDS
VOCs are emitted as gases and are made up of a number of components, including a high amount of carbon. VOCs are commonly scattered throughout the atmosphere and are often the cause of odours in the air. They can be produced naturally (mostly from plants) as well as from human activity, including coal combustion. VOCs contribute to the formation of photochemical smog.32
Very little is known about the health effects of VOCs released from coal mine fires.33 The release of these elements represents an unquantifiable contribution to the additional health risks associated with the mine fire. One VOC that is a known human carcinogen is benzene, which is a chemical found in environmental tobacco smoke, stored fuels, and exhaust from cars.
Ozone is a gas that is formed by the chemical reaction of VOCs and nitrogen dioxide in sunlight. It creates photochemical smog. Ozone has a sharp odour similar to chlorine, and is easily detectable even in small concentrations. The environmental effects of ozone include damage to vegetation, such as stunted tree growth.34
The known potential human health effects of ozone include:
- throat irritation
- pain, burning, or discomfort in the chest when taking a deep breath
- chest tightness, wheezing, or shortness of breath
- increased asthma attacks and hospital admissions for respiratory illness.35
POLYCYCLIC AROMATIC HYDROCARBONS
PAHs are found in coal and other fossil deposits and can be generated, for example, when meat is cooked at very high temperatures. In addition to being found in raw coal, PAHs are a component of particulate matter produced from incomplete coal combustion (as was the case in the Hazelwood mine fire). Different types of combustion or burning produce different types of PAHs.36
The health effects of exposure to PAHs are unclear. However, some studies have linked prenatal exposure to PAHs with low birth weight.37
DIOXINS AND FURANS
Dioxins and furans are environmental pollutants found in a number of sources, including animal products. They are also produced by industrial processes (including coal-fired power stations), and fires that involve carbon (including coal fires). They are commonly found in air, soil, sediments and food. Dioxins and furans are introduced into the environment through the atmosphere as trace products of combustion. Dioxins and furans are harmful to wildlife and livestock.38
The known potential human health effects of dioxins and furans include:
- skin lesions (short-term exposure)
- immunotoxicity (long-term exposure)
- developmental and neurodevelopmental effects (long-term exposure)
- thyroid effects (long-term exposure).
The group most vulnerable to dioxins and furans is unborn babies.39
Heavy metals (such as magnesium, manganese, mercury and zinc) do not break down in the environment, and some accumulate in plants and animals if they cannot be excreted.40 Plants and animals can be poisoned by small amounts of heavy metals that accumulate over long periods of time or through ongoing exposure.41 The concentration of these elements in ambient (outdoor) air may contribute to particulate matter toxicity.42
INTERACTIONS OF AIR POLLUTANTS
Air pollutants can interact in the air as well as at the biological level (in humans, animals and plants). Interactions between air pollutants change the toxicity of the pollution mixture.43
Professor Campbell told the Board that very few epidemiological studies have examined the adverse health potential of ‘mixed’ pollutants. He also advised that in an uncontrolled setting, the mixture of pollutants makes it difficult to determine either the independent or synergistic effects of ambient air pollutants.44