Why are they hazardous?

Arsenic is toxic and large doses may be fatal. Repeated small doses are also likely to be harmful. Arsenic cannot be efficiently removed from the body and may accumulate leading to serious illness. Long-term exposure is known to cause cancer.

A potential way to be exposed to arsenic in museum collections is by handling objects that are contaminated with historic arsenic pesticide and preservative treatments. Handling such objects without adequate precautions will increase the risk of exposure to small amounts of arsenic by ingestion, inhalation or direct contact with the skin.