Experts say a huge orange dust storm rolling through Australia's east coast is lining up to become one of the largest on record.

The storm is a major health hazard for people with lung problems and is stripping valuable topsoil from farms.

It has swept up enough dust every hour to fill thousands of semi-trailers and has blanketed Sydney in a grainy haze, disrupting air traffic and port operations.

Dr John Leys, the southern program coordinator of scientific program Dust Watch, says it is the worst measured storm in seven years of monitoring and the largest to reach Sydney since the 1960s.

However, he says radio callers are correct in pointing out that dust storms used to be more common.

"There used to be a lot more dust storms more frequent in the past and they were like this, but they often didn't come this far into Sydney," he said.

"In fact, the number of dust storms was getting less and less through time.

"Certain parts of the landscape will suffer nutrient loss and soil loss - some of those won't recover but the vast majority will. It is not a complete disaster."

Dr Leys says a number of dust storms have been raging in South Australia for several weeks and have now pushed out towards the east coast.

But he says land management is constantly improving, which is helping to reduce the impact of dust storms.

Concern for agriculture

Judith Hams, who lives on a farm about 100 kilometres from Broken Hill, says the dust storms have had a huge impact.

"We were really dry, we've only had about 70 millimetres for the year and we were starting to feed stock," she said.

"We also sold a lot of our stock because of the drought and most of the little bits of grass that were trying to grow and herbage that was trying to survive will be destroyed with the wind from last night. It was just a cutting wind that took everything with it."

Stephen Cattle, a senior lecturer of soil science at Sydney University, says that is a real concern for agriculture.

"The top soil is often some of the better soil because lower down the soil becomes a bit more salty, a bit more sodium rich and not so hospitable for plant growth," he said.

"So by losing the top soil in particular, where most of our organic matter resides, most of our organic carbon resides, it represents quite a loss to the potential productivity of that soil."

Dr Cattle says overgrazing can cause disruption of the topsoil, but if farmers do not over-cultivate the land, the storm will be better able to resist wind erosion.

"I think we pretty much all understand that Australia is generally an arid continent and so from time to time, when the rain doesn't fall and the wind howls, then these dust storms are going to occur," he said.

"So to an extent we can control the severity of these storms, but at the end of the day nature will always win."