This is a transcript from PM. The program is broadcast around Australia at 5:10pm on Radio National and 6:10pm on ABC Local Radio.

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BRENDAN TREMBATH: Several piggeries in Western Australia are in quarantine because lead was discovered in a feed supplement brought in from China.

The Pig Breeders Association fears that dozens of piggeries in the state could be affected.

Western Australia's agriculture department says there's no threat to the public and that contaminated pigs can be sold for slaughter.

David Weber reports.

DAVID WEBER: The Pig Breeders Association says it doesn't know how the lead got into the supplement.

The association's WA branch president Judy Pearce.

JUDY PEARCE: One of the ways is maybe contamination from their warehousing or it could've not been mined in a very decisive manner because lead is a component of the nutrients that come out of the ground for various things and they are separated usually by heating in a furnace.

DAVID WEBER: How was the lead contamination discovered?

JUDY PEARCE: By random analysis from Linley Valley, which is where they kill the pig meat.

DAVID WEBER: So this might have happened before without anybody knowing?

JUDY PEARCE: As I understand it this was the first shipment of zinc oxide from China.

DAVID WEBER: Will it affect other piggeries besides these half a dozen as it currently stands in Western Australia?

JUDY PEARCE: Well they're saying that it may be up to 80.

You've got to understand some people have used it just as a feed additive and some have used it as a growth promotant. Now when it is used as a growth promotant it's given many more times than you would take it yourself or anyone else would and therefore it becomes a growth promotant because of its innate quality of cellular building in the muscle.

DAVID WEBER: And potentially the lead contamination would be worse in those situations?

JUDY PEARCE: Yes. And also what you've got to understand is that it is residual.

DAVID WEBER: The WA Department of Agriculture says the zinc oxide supplement has been recalled, and there's no threat to the public.

The department says all farmers that bought the supplement have been advised.

The livers and the kidneys of the pigs have been condemned, but not the flesh.

The director of Animal Biosecurity, Dr Ashley Mercy.

ASHLEY MERCY: We've actually tested the pigs from one of the exposed piggeries and they do have levels of lead in their livers but in the muscle of those pigs, all of the pigs that were tested and there's some 24 of them had no levels of lead in their muscles and we have got a statement from the Department of Health WA to say that the pig meat from these piggeries pose no health risk to humans.

DAVID WEBER: The meat is OK because the lead gets into the liver and not the muscles?

ASHLEY MERCY: That's correct. That's correct. The lead when it's consumed by an animal gets stored in the liver so they're a pretty good signal as to what's happening, or the bone.

DAVID WEBER: Doctor Mercy says all the feed manufacturers in Australia have been advised of the incident.

He says they may need to do their own testing to ensure there's no contamination.