Wool can become contaminated with arsenic in various ways, and several different sources may each contribute to any individual arsenic residue problem.
• dipping sheep in an arsenical dip ( now illegal),
• dipping sheep in a non-arsenical dip in a contaminated dipping facility
• penning sheep on soil with high levels of arsenic before shearing.
Other possible sources include running sheep on land contaminated by gold mine tailings or exploration sites, and allowing sheep access to sites on the farm where arsenical compounds have been dumped, for example, rubbish dumps or sites where dip/sump sludge has been dumped.
Farmers can prevent wool arsenic levels above the Industry Standard by soil testing and sensible management of their dip and yards.
Martin, Tony; Jacob, Robin; Davies, Marion; and Rutherford, Peter
"How arsenic residues get in wool,"
Journal of the Department of Agriculture, Western Australia, Series 4: Vol. 33
, Article 8.
Available at: http://researchlibrary.agric.wa.gov.au/journal_agriculture4/vol33/iss2/8