Residential homes that have once been used as methamphetamine labs can still hold contaminated air years after changing hands, new research has found.

Simply breathing inside these houses can therefore expose someone to traces of meth. Even after moving house, these potentially toxic chemicals can stick to furniture, clothes, and soft toys, leaching back into the air.

The study is based on two different homes in Australia, each of which housed a meth lab before being sold to new tenants.

For nine years, a family with two young children lived in the first home, without even knowing it was contaminated, although the tenants did report feeling unwell whilst living there, especially the kids.

Meth residues were later found on surfaces throughout the home at a rate of 12.6 µg/100 cm2 on average, and concentrations of meth in the air hung at 4.7 µg/m3.

According to the authors, that's on par with active meth labs seized by United States officials, and yet no current risk guidelines take these air pollutants into account.

While it's not clear if breathing these toxins directly caused any of the adverse health effects the family experienced, the concentrations of the drug were well above surface residue guidelines.

"Australian guidelines currently allow for the assessment of methamphetamine in contaminated properties, or properties contaminated with other illicit drugs, but ignore inhalation exposure," says environmental health scientist Jackie Wright from Flinders University.

"These policies can significantly underestimate the risks in former meth houses when new owners aren't aware, and therefore indicate the guidelines don't currently address protective health measures."

The contamination of residential homes with meth, more colloquially known as 'ice' or 'speed', has only recently emerged as a public health issue, impacting thousands of houses in the US alone.

Today, most research has focused on the sticky toxic residues left on surfaces from meth manufacturing, but smoking or cooking meth can also produce potentially dangerous residue in the air.

While touching contaminated surfaces is thought to be the biggest threat for young children, the authors of this new research found breathing alone might have accounted for up to 20 percent of the children's meth exposure in house number one.

On the other hand, for adults living under the same roof, breathing contaminated air made up roughly 60 percent of their meth exposure, with the rest coming from skin absorption or even ingestion of residue from hands.

"While this data is from one property," the authors write, "the data indicates that not accounting for the inhalation of methamphetamine in properties that have not been remediated may significantly underestimate potential exposures."

The second home analysed in the study offers even more concerning data. Researchers were not able to test the house directly, as the tenants had since moved out, but their possessions, including clothes and soft toys, still held traces of meth.

When these items were placed within sealed bags, the authors found they leached traces of meth back into the air, creating opportunity for further spread.

Over the years, living in a house with high surface residue for meth has been linked to a host of adverse health effects, including headaches, respiratory problems, and skin irritation.

Unfortunately, data on meth exposure and its direct health effects remains uncertain, and apart from mice studies, case reports are some of the best evidence we've got.

In 2015, a study found one Australian family living in a former meth lab had been so deeply exposed, every single member suffered ill health while living there. The youngest child, aged 7, was impacted the worst, with asthma-like symptoms, trouble sleeping, and behavioural changes.

Samples taken of their hair revealed the two youngest children had meth levels in the range of chronic adult drug users or children living in active meth labs. Their home had an environmental methamphetamine surface contamination level only slightly above what was found in the current study.

Public policy on meth labs and housing is still catching up with the science, and the new research suggests we need to expand our rules. The whole home needs to be tested for meth, not just the room it was cooked in, the authors argue - and not just the surfaces, but also the ambient air and our own possessions.

The study was published in the Journal of Exposure Science & Environmental Epidemiology.