What bushfire smoke is doing to our health
Sydney is once again shrouded in smoke raising questions about potential health risks. (Nine)
Hazy skies and smoky air has become the norm in recent days for millions of Australians living in cities and towns affected by the bushfire emergency.
Stinging eyes and a raw throat are not the only potential health effects of the pollution, which authorities warn could get worse during summer.
What is bushfire smoke and why is it dangerous?
Smoke from bushfires is made up of small particles, gases including carbon monoxide, carbon dioxide, nitrogen oxides, and water vapour.
The larger particles visible to the eye contribute to the visible haze when a fire is burning. They are generally too large to breathe deeply into the lungs but can irritate the nose and throat.
Fire smoke also contains finer microscopic particles and gases that are small enough to breathe deep into the lungs. It is these particles that can pose a threat to people's respiratory health.
Sydney's air has previously ranked within the highest air-quality category of zero to 50 on the air quality index (AQI), but the bushfire emergency has sent the city's reading plummeting in recent days.
Today's air quality rating in Sydney is 154, categorised as 'unhealthy', which AQI officials define as "everyone may begin to experience health effects; members of sensitive groups may experience more serious health effects".
Lung Foundation chief executive Mark Brooke said if people have been experiencing an itchy throat or eyes, a runny nose or are feeling more breathless than usual, these could be symptoms of smoke inhalation.
"When you inhale smoke, particulates get into the back of your throat and nasal tracks and cause irritation and even get right down into the lungs themselves and cause damage," he said.
Is breathing in bushfire smoke really as bad as smoking cigarettes?
National Asthma Council chief executive Siobhan Brophy said that while bushfire smoke can be damaging, comparisons to inhalation cigarette smoke is a step too far.
"When you smoke a cigarette you're not breathing in burnt leaf, which is basically what you're doing when you inhale bushfire smoke," she said.
"Cigarettes have all kinds of other chemicals that make them particularly bad for your health - but either way, neither is good for you."
Mr Brooke said the impacts of smoke inhalation would be different for different people depending on factors including age and respiratory health.
But inhaling any type of toxic is a risk.
Although smoke inhalation can pose health risks, some experts suggest smoking cigarettes is still worse. (Supplied)
"We would rely on the premise that breathing in anything other than clean air is bad for you and you should be doing everything to reduce your exposure," said Mr Brooke.
"The evidence suggests that any prolonged exposure to polluted or toxic air is if harmful over time but if your taking necessary preventions the vast majority of Australians with healthy lungs will get through this type of event," he said.
"'It's those that have compromised lungs that we are most concerned about, particularly the elderly," he said.
How long will the smoke last and what should you do until then?
Smoke from Australia's bushfires has reached New Zealand for the second time since they began, Weatherzone said.
"The fires have been ejecting masses of smoke and ash into the atmosphere for a number of months," the statement said.
"This week, persistent westerly winds have allowed a large mass of smoke to drift across the Tasman Sea, where it could be seen passing over New Zealand's North Island on Thursday."
Forecasts indicate smoke haze will remain over many parts of NSW including Sydney for the remainder of the week and over the weekend.
Meteorologist Helen Kirkup from the BOM says the answer to when the haze will lift is straightforward – the smoke won't stop until the fires do.
"The only way the smoke stops is with rain and a lot of it," she told Nine.com.
"Wherever there's fire, there's smoke and wind changes might provide some temporary relief to certain places but that also just fans smoke which can just make things worse," she said.
Until conditions improve, Mr Brooke is urging everyone to take extra precautions to protect their health.
"Aside from reducing your exposure to smoke, it's really important to contact your GP or health specialist and make sure your medication are up to date," said Mr Brooke.
"If you're feeling unwell or you're feeling breathless, you need to seek medical attention.
"Also, if you've got an elderly resident, neighbour or family member, check in on them frequently when our air quality is poor. This is so important in preventing tragedies."
Siobhan Brophy said it's important people stay active, particularly If they have conditions like asthma, but should avoid doing vigorous exercise outdoors.
"This is the time to take the kids to the library or try an indoor rock-climbing wall instead of running around in the park because this kind of air is not good for you," she said.