Doctors have a responsibility to speak out about the dire health impacts of climate change, an expert says, as bushfires burning across NSW create hazardous air pollution in Sydney.
Air quality was hazardous in northwestern Sydney on Tuesday morning and between very poor and hazardous in central and eastern Sydney.
Public health physician Dr Kate Charlesworth says the medical profession has an obligation to discuss the link between climate change and poor health.
"From a health perspective, refusing to talk about these bushfires is like refusing to talk about smoking and lung cancer," she told AAP.
"There's a proud history of health professionals standing up on issues of importance - think of asbestos and tobacco control - that is our role."
Dr Charlesworth says doctors are increasingly seeing the health impacts of climate change on patients and speaking up is "part of our duty of care".
The Doctors for the Environment Australia members said poor air quality caused by bushfire smoke puts vulnerable groups at risk, including people with pre-existing heart and lung disease as well as the elderly, babies and young children.
"The key thing is people need to keep their medication at hand - they need to stay indoors, avoid exercise, and see their doctor if they feel it's necessary," Dr Charlesworth said.
Hazardous air quality levels were reported across Sydney at the height of "catastrophic" bushfire conditions experienced last week.
Poor air quality driven by more frequent and more severe bushfires will put an increasing burden on the state's health services, Dr Charlesworth argues.
"The evidence is overwhelming that we have a climate emergency and we need an appropriate response."
NSW Health says those with conditions such as asthma, emphysema and angina are particularly sensitive to the effects of smoke.
Air quality was hazardous in the Northern Tablelands and the northwest slopes on Tuesday and poor in the Hunter region, the Central Coast and Illawarra.
The Bureau of Meteorology says bushfire smoke will ease in Sydney during the day but later worsen again on Tuesday night.