Using standards to protect the community In order to protect the community from acute health effects due to CO, air quality will be monitored in communities likely to be impacted by smoke from fires with the greatest CO producing potential. Results of this monitoring will be assessed continually to ensure that early preparation for appropriate community messaging and action will take place well prior to the threshold being reached. CO monitoring will continue to ensure that community health is protected until the fires are sufficiently controlled. The concentration of CO in the air fluctuates continuously, with frequent spikes in concentration. As concentrations of CO in the air will vary from moment to moment, averaged values will be calculated. Research has shown that very brief exposure to highly elevated CO concentrations during moderate overall CO exposure does not necessarily result in harmful thresholds being exceeded10. The averaged values will be considered in relation to the thresholds specified in AEGL-2, with information about the likely duration of the fire, the fire suppression strategy, and predictions about future wind and weather conditions. If the duration of exposure to elevated levels of CO is a risk to community health, a number of options to protect the community are available. Options to protect the community Options to protect the community from prolonged exposure to high levels of CO include: Advice increased levels of CO and the need to minimise physical activity and stay aware of further alerts. Warning with instructions to take shelter indoors until conditions improve or further advice is received. Emergency Warning - to relocate or instruct to take shelter indoors. Evacuation (‘prepare to evacuate’ and ‘evacuate now’) – specific instructions on where to go, how to get there and what to take are provided in the warning. Information issued to the community, as described above, will be issued when it is predicted that the relevant AEGL-2 threshold will be exceeded, according to the expected duration of the impact on the community. Decision making is based on both observed and predictive information which includes Measured results adjusted to hourly averages from monitoring Bureau of Meteorology forecast data Fire behaviour both actual and forecast Predicted duration of prevailing conditions and elevated levels Size of community impacted Any warning will be issued in anticipation of a relevant AEGL-2 threshold being exceeded, adjusted for the known effectiveness of shelter-in-place strategies. In other words, one to two hours prior to the anticipated time that the threshold will be exceeded. 10Reisen F, Mayer M, Hansen D. Carbon monoxide – hazard on the fire ground (Bushfire CRC, 2008)
CO – Acute poisoning The appearance of symptoms in someone suffering from acute exposure is dependent on the following: The concentration of CO in air breathed The duration of exposure The degree of physical exertion Individual susceptibility Pre-inhalation COHb level 15 Susceptible individuals include the following16: Pregnant women – because of potential harm to the foetus from low levels of oxygen People with anaemia (low blood count or Hb concentration) - because of lowered oxygen carrying capacity of the blood People who have cardiovascular or heart conditions, especially angina People who have breathing disorders and lung disease Smokers because they may have high levels of CO in their blood before they are exposed to contaminated air Table 2: Summary of acute health effects of carbon monoxide17 COHb Concentration % Principal Signs and Symptoms < 2 No significant health effects 2.5 – 5 Decreased exercise duration due to increased chest pain (angina) in patients with cardiovascular disease. No significant health effects expected in rest of population 5 – 10 Subtle neurobehavioral symptoms 10 – 20 Headache (“frontal tightness”), possible shortness of breath in healthy population. May be lethal for someone with severe disease. 20 – 30 Throbbing headache, nausea, flushing 30 – 40 Severe headache, dizziness, nausea, rapid breathing >40 Collapse, coma, convulsion, death This is given as a guide only and there may be considerable variation depending individual characteristics. 15 Hazardous Substances Information System (HSIS); Exposure standard documentation: Carbon monoxide (Safe Work Australia 1996) 16 S Bull; HPA Compendium of Chemical Hazards: Carbon monoxide (UK Health Protection Agency 2011) 17 Adapted from S Bull; HPA Compendium of Chemical Hazards: Carbon monoxide (UK Health Protection Agency 2011); and the Agency for Toxic Substances and Disease Registry; Toxicological Profile for carbon monoxide (US Department of Health and Human Services, June 2012)