A joint statement signed by 22 organisations has labelled Sydney's poor air quality a "public health emergency" that requires urgent government action, as NSW braces for more smoke and a looming heatwave.

Released by the Climate and Health Alliance on Monday, with signatures from the Royal Australasian College of Physicians, Australasian College of Emergency Medicine, Public Health Association of Australia and 19 other organisations, the statement said "there is no safe level of air pollution".

Hazardous pollution levels are linked to "premature births, low birth weight babies, impaired lung development in children, asthma, heart disease, stroke, chronic obstructive pulmonary disease and lung cancer," the statement said.

It urges NSW Premier Gladys Berejiklian and Prime Minister Scott Morrison to show leadership and "implement measures to help alleviate the health and climate crisis" – including the development of a national strategy on climate and health.