61. Women who worked in munitions factories in England during World War I were nicknamed "canaries". Why was this?
From Quiz Potpourri Number Five
Answer:
Their skin became yellow from the TNT powder
During World War One, many of the women working in munitions factories in England making bombs, other explosive devices, and even aeroplanes, were, like most factory workers, from the lower classes. This was hardly surprising as those families needed all hands on deck to feed their broods. Working with the dangerous fumes and chemicals involved in TNT though was dangerous at the best of time, with these women, also known as "canary girls", returning home most days with the skin on their faces and hands tinged yellow. Illnesses these products could cause, according to the British Medical Journal of 1 April, 1916, were "headaches, eczema, loss of appetite, cyanosis, shortness of breath, vomiting, anaemia, palpitation, bile stained urine, constipation, rapid weak pulse, pains in the limbs and jaundice and mercury poisoning". Children born to many of these women were also often tinged yellow, and, as a result, became known as "canary babies".
(Thanks to WaggaWagga2010 for the information regarding this question)