Blue People

The appearance of people exposed to concentrated sodium nitrite, which oxidises haemoglobin to methaemoglobin, resulting in a dusky blue-grey skin colour; patients with congenital methaemoglobinemia are at risk for haemoglobin oxidation by nitrites; other risk groups include dynamite workers, amyl nitrite ‘poppers’, cardiac patients treated with nitroglycerin, and newborns—erythrocyte cytochrome B5 reductase is low