A conference on air pollution has been told that 40 per cent of Perth children suffer from asthma by the time they reach six years of age.

Professor Peter Sly, from the Institute For Child Health Research, was a keynote speaker at the conference organised by the Conservation Council.

He revealed the figures.

Council spokeswoman Sue Graham-Taylor says there can be little doubt most of the blame lies with atmospheric pollution.

She says children are no safer inside the family home.

"The impacts of the products we use, the furniture we buy, the paints we use, the formaldehyde, the glues in our furniture, the impacts on our health can hang around for years," she said.

"I was quite alarmed at the fact that tobacco smoke is still a major factor and just our general lifestyles, in our homes."