The air pollution following the dust blown across parts of England and Wales from the Sahara hit the county of North Yorkshire, including the Harrogate district, last week.
Experts warned early in the week that the dust would travel north as a result of south-easterly wind and continental flow, though it was expected to dissipate by the weekend.
High levels of pollution coincided with a high number of 999 calls to ambulance services throughout England including Yorkshire, where calls reporting breathing difficulties rose from 384 to 443, between Monday and Wednesday, of last week compared to the previous week.
A spokesman for Yorkshire Ambulance Service NHS Trust said: “During the period of Monday March 31 to Wednesday April 2, we received 443 emergency calls relating to breathing difficulties.
“This was an increase of around 15 per cent on the same time period of the week before.
“Although this increase in 999 calls coincided with recent air pollution warnings, we cannot say definitively whether it was this factor alone that caused the increase.
“Therefore, the figures cannot be directly attributed to the recently reported issues with air quality.”
The London Ambulance Service said it saw a 14 per cent increase in emergency calls for patients with breathing problems last Thursday, rising from an average of 200 normally to 227 calls.
Ambulance services in the West Midlands and East England also said they had seen a spike in the number of reported breathing problems.