NSW dust storm: spike in reports of breathing difficulties as 'hazardous' front descends on Sydney

City's skyline changes colour as line of dust more than 500km long sweeps east

A thick line of dust that has smothered much of New South Wales and Sydney has caused air quality to reach a "hazardous" level with another wave of dust set to come, leading to a spike in calls for help from people with breathing difficulties.

Strong winds from a low pressure system have whipped up masses of dirt across the drought-stricken state, which headed towards the coast on Thursday.