Your crops are safe from asbestos
Shirley Bullet, of Otorohanga, asked:
Is it safe to plant an edible crop such as potatoes under the eaves of the house which recently had its asbestosbased roof replaced?
Derrick Moot, professor in plant science at Lincoln University, responded:
Asbestos, referring to a group of naturally occurring silicate minerals, was used to build a lot of roofs or wall claddings in New Zealand. It is a safe product when it is in sheets on your roof. When the roof is removed, however, there is a small chance that those sheets get broken and then tiny asbestos fibres, not visible to the human eye, can be dislodged and float in the air. If these needlelike fibres are breathed in they may damage lung tissue. It is dangerous solely when it is inhaled. To avoid breathing in the fibres the professionals removing the roof wear protective clothing and special breathing masks. They take care not to break the sheets so there are no fibres. Once finished they also check that there are no asbestos fibres in the air or on flat surfaces like window ledges. This means you can safely breath the air in and around your house after your roof has been replaced.
Any plants grown after the roof is replaced are also not exposed to asbestos. Unlike common chemical contaminants, asbestos fibres do not migrate (except if the ground itself moves), hence do not leak into the groundwater. The only asbestosrelated hazard of contaminated soil is that it releases airborne fibres. Luckily, even small amount of soil moisture content suppresses this risk significantly.
Plants do not take up asbestos from the water or soil so it does not accumulate in the food chain. The eaves provide shelter and a warmer place than the garden for plants, like potatoes and tomatoes, to grow, especially in cooler winter months.
Send questions to: AskAScientist, PO Box 517, Dunedin 9016 Or email: question.aas@gmail.com