Forty-eight hours after inhaling passive smoke you could come up positive.

"It is not clear, though, what the potential risk of combined passive smoke and radon is to non-smokers and children."

Back in my day we exposed children to passive smoke all the time...

"Among those exposed to passive smoke," the researchers wrote, "children are especially vulnerable."

People in the UK are being increasingly protected from passive smoke, but it is solely due to voluntary action by companies.

Tobacco industry spokesmen say that passive smoke may be a nuisance but is not harmful.

Some patients report that even exposure to passive smoke can be enough to trigger or worsen attacks.

Exposure to environmental tobacco smoke, also known as passive smoke, is a significant additional cause of death, disease and disability in the European Union.

The researchers found that the greater the exposure to passive smoke, the greater were the biochemical changes.

Researchers say that young children may develop symptoms after exposure to passive smoke for only a few months.