25 March 2014

Mould in your home raises your asthma risk

Middle-aged people who have mould in their homes have a higher risk of asthma, and men are especially vulnerable.

Mould exposure in the home raises the risk of asthma symptomsin middle age, according to a new study from Australia.

The more mould participants reported having seen in their homes, the greater their asthma symptoms, researchers found. Men were especially vulnerable with a four-fold increase in the odds of having non-allergic asthma after recent exposure to visible mould.

"The mould exposure that we were talking about is the typical mould that we all see in our homes from time to time, that is, mould that you see in the wet areas of the house, e.g., bathroom, kitchen and laundry," John Burgess told Reuters Health in an email. Burgess, a researcher with the Melbourne School of Population and Global Health at the University of Melbourne, co-led the study with colleague Desiree Meszaros.

Read: What are the symptoms of asthma?

25 million Americans have asthma

"We were not talking about 'whole-house' mould infestation that might occur under special circumstances such as following the house being flooded," Burgess said. While a number of previous studies have examined indoor air pollutants and asthma, the majority focused on children and adolescents, Burgess said, but little research has looked at the relationship between these exposures and asthma in middle-aged adults.

About 25 million Americans have asthma, according to the National Heart, Lung and Blood Institute, and 7 million of them are children. Asthma typically begins in childhood, and often occurs in kids with allergies. Burgess and his colleagues were interested in the effect of indoor air pollutants on adults' asthma symptoms and also in any differences between responses by those with allergic asthma and those with non-allergic asthma.

"We did this because in older adults, all asthma is not necessarily the same," Burgess said. "In this age group, non-allergic asthma is more common – we surmised that the risk of having 'non-allergic asthma' related to indoor air pollutants might be increased in this older population." The research team used data from an ongoing study that began in 1968 when the participants were seven years old.

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In 2004, a total of 5 729 participants filled questionnaires about a variety of health topics, including respiratory symptoms and their home environment. Participants were asked about asthma, asthma symptoms, amount of visible mould in the home, the number of smokers and types of heating and cooking appliances they had.

About 11.6% of the participants had asthma at the time of the 2004 questionnaire. About 17% had chest tightness at night and 23% reporting wheezing during the previous year. About 30% of the participants were smokers and about 15% of households included at least one regular smoker other than the study participant.

Wheezing and chest tightness

Almost half reported ever having had mould on any home surface, and about a third said they'd seen mould at home within the last 12 months, according to the results published in Respirology. Recent household mould exposure was associated with 26% greater odds of having asthma, 34% greater odds of wheezing and 30% greater odds of chest tightness.

The authors noted that the more rooms with mould, the worse the asthma symptoms. For men, mould exposure was linked to almost four times greater odds of having non-allergic asthma, but not for women. The researchers also found that second-hand tobacco smoke was associated with increased odds of asthma, wheezing and chest tightness in non-smokers.

Read: Mouldy home tied to kids' asthma, allergies

"We did not find any evidence that the type of stove used in the home for cooking had any effect on asthma," Burgess said. "But we found that having a reverse cycle air conditioner in the home was linked with a 16% reduction in the risk of asthma."

The US Environmental Protection offers tips for mould control. Burgess said that to find mould, homeowners should "have a look and have a sniff!" Most household mould is black, green or yellow and is visible, he said, adding that mould smells. "We all know the dank smell from mould, so if your nose says mould, you probably have a mould problem," he said.

Well ventilated and dry

Getting rid of mould involves two steps, Burgess said. "First is cleaning it off household surfaces – don't use a dry scrubbing brush – that just spreads the mould around," he said. "And second is ensuring that the room in question is well ventilated and dry. Mould won't grow in dry, well ventilated areas."

Burgess said that methods to actually kill mould spores are debated, with some mould removal experts advising that bleaches will kill mould, while other experts assert that bleaches merely discolour the mould and doesn't kill it. "For most domestic mould, keep it simple – clean it off and make sure that the place remains dry and well ventilated," he said.

Read more:
Mould may trigger severe asthma
New asthma research breaks the mould
Mouldy homes trigger asthma


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Professor Keertan Dheda has received of several prestigious awards including the 2014 Oppenheimer Award, and has published over 160 peer-reviewed papers and holds 3 patents related to new TB diagnostic or infection control technologies. He serves on the editorial board of the journals PLoS One, the International Journal of Tuberculosis and Lung Disease, American Journal of Respiratory and Critical Medicine, Lancet Respiratory Diseases and Nature Scientific Reports, amongst others.Read his full biography at the University of Cape Town Lung Institute

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