Cleaning the house is as bad for women's lungs as smoking up to 20 cigarettes.

Cleaning the house is as bad for women's lungs as smoking a packet of cigarettes a day, a study has found.

But using cleaning products had no effect on men's lungs, research showed.

Researched assessed the lungs of 6,235 women and men at 22 centres – and then checked on them again over the course of twenty years.

They were asked whether they cleaned their own house, or whether they worked as professional cleaners.

They were also asked how often they used liquid cleaning products and sprays.

The research found that women who cleaned – either around the house as little as once a week or as professional cleaners - had an 'accelerated' decline in lung capacity.

The drop in lung function in both groups was comparable to smoking a pack of 20 cigarettes for between 10-20 years.

The authors warn that cleaning for women 'may constitute a risk to respiratory health'.

No effect was found on the lungs of men who did the cleaning – either professionally, or just as part of their domestic chores.

The authors – led by researchers at the University of Bergen – said that a variety of potential irritants to the lungs are found in domestic products – including bleach and ammonia.

Participants were asked if they used 'sprays, or other cleaning agents'. No significant difference was found between using cleaning sprays and cleaning liquids – a surprise to the researchers who expected sprays to have more impact on the lungs.

The authors write: 'Women cleaning at home or working as occupational cleaners had accelerated decline in lung function, suggesting that exposures related to cleaning activities may constitute a risk to long-term respiratory health.'

Explaining the medical effects on the lungs, the researchers said 'low-grade inflammation over many years could possibly lead to persistent damage to the airways, alternatively, persistent damage could result from continued exposure after onset of cleaning-related asthma.'

They added that it was well documented that 'airway irritants such as ammonia and bleach' (both found in household products such as bleach and toilet cleaner) cause 'fibrotic' changes to the lung tissue – scarring of the lungs.

The cleaning products may both irritate the lungs and cause persistent changes over time.

Dr Cecile Svanes of the University of Bergen, who carried out the study said: 'While the short-term effects of cleaning chemicals on asthma are becoming increasingly well documented, we lack knowledge of the long-term impact.

'We feared that such chemicals, by steadily causing a little damage to the airways day after day, year after year, might accelerate the rate of lung function decline that occurs with age.'

The researchers suggest that people should use bleach to clean less - as 'water and a microfibre cloth' are sufficient for most cleaning tasks.

Researchers at the University of Bergen in Norway based their results on data from 6,235 participants in the European Community Respiratory Health Survey. The participants, whose average age was 34 when they enrolled, were followed for more than 20 years.

In the study, 1,512 men never cleaned the house, compared to just 197 women. Of those who cleaned at home, there were 1,363 women and 2,808 women.

Professional cleaners comprised 57 men and 293 women.

The researchers found that 12.3 per cent of women who cleaned at home and 13.7 per cent of women who cleaned at home developed asthma, compared to 9.6 percent for women who did not clean.

Co-author Oistein Svanes, said the level of impact on cleaning products was seen as surprising at first.

But he added: 'However, when you think of inhaling small particles from cleaning agents that are meant for cleaning the floor and not your lungs, maybe it is not so surprising after all.'

The authors suggest that the reduction in lung capacity happens because cleaning chemicals irritate the mucous membranes lining the airways, which over time results in persistent changes in the airways.

The study also found that men who cleaned regularly were not affected by using cleaning products.

They suggesetd that this may be because men's lungs are less susceptible to the impact of cleaning chemicals. Previous research has found that male lungs are more resistant to damage from various irritants including tobacco smoke and wood dust.

He added: 'The take-home message of this study is that in the long run cleaning chemicals very likely cause rather substantial damage to your lungs. Dr Svanes, a respiratory consultant, added: 'These chemicals are usually unnecessary; microfibre cloths and water are more than enough for most purposes,' with the exception being cleaning the toilet when bleach may be necessary, he said.

He added that public health officials should strictly regulate cleaning products and encourage producers to develop cleaning agents that cannot be inhaled.

Dr Samantha Walker, Director of Policy and Research at Asthma UK says: 'Cleaning products can be toxic for people with asthma as they often contain chemical compounds that can inflame the airways, leaving people prone to an asthma attack.

'It is deeply concerning that this study shows cleaning products can cause long-term lung damage for people with asthma.

'At Asthma UK we'd advise people with the condition who do a lot of cleaning to speak to their GP or nurse about what they can realistically do to reduce the risk of having an asthma attack. 'This could include using solid or liquid cleaning products instead of sprays, avoiding scented products and ensuring the area where they clean is well-ventilated.'