When cyanide is ingested, it binds to iron inside cells, interfering with the absorption of certain enzymes and compromising a cell’s ability to produce energy. Cyanide affects the tissues most needed for aerobic respiration, the heart and lungs. In high doses cyanide can bring on seizures, coma, and then cardiac arrest, killing quickly. At lower doses cyanide leads to weakness, giddiness, confusion, and light-headedness. Exposure to even low levels of cyanide over long periods of time can lead to permanent paralysis. Fortunately for the tea drinkers of Britain, Prussian blue is a complex molecule, so it is almost impossible to release the cyanide ion from it and the poison passes harmlessly through the body.
Elsewhere in the factory, however, over the charcoal fires where the tea was roasted, Fortune discovered a man cooking a bright yellow powder into a paste. The smell was terrible, like that of rotten eggs. The yellow substance was gypsum, or calcium sulfate dehydrate, a common component of plaster. Gypsum produces hydrogen sulfide gas as it breaks down. While the gas is produced naturally by the body in low doses, in high doses it acts as a broad-spectrum poison, affecting many of the body’s systems simultaneously, particularly the nervous system. At lower concentrations gypsum acts as an irritant; it reddens the eyes, inflames the throat, and causes nausea, shortness of breath, and fluid in the lungs. Consumed over the long term it might produce fatigue, memory loss, headaches, irritability, and dizziness. It can even induce miscarriage in women, and failure to thrive in infants and children.
Fortune estimated that more than half a pound of plaster and Prussian blue was included in every hundred pounds of tea being prepared. The average Londoner was believed to consume as much as one pound of tea per year, which meant that Chinese tea was effectively poisoning British consumers. The additives were not included maliciously, however, for the Chinese simply believed that foreigners wanted their green tea to look green.
“No wonder the Chinese consider the natives of the West to be a race of barbarians,” Fortune remarked. But why, he asked, were they making green tea so extremely green, since it looked so much better without the addition of poison and since the Chinese themselves would never dream of drinking it colored?
“Foreigners seemed to prefer having a mixture of Prussian blue and gypsum with their tea, to make it look uniform and pretty, and as these ingredients were cheap enough, the Chinese [have] no objection to [supplying] them as such teas always fetch . . . a higher price!”
Fortune surreptitiously collected some of the poisonous dyes from the factory, bundling them up in his wax-dipped cloth sacks and stowing them away in the generous folds of his mandarin costume. As a scientist he wanted samples to analyze, but most of all he wanted to send additional ones back to England.
These substances would be prominently displayed in London’s Great Exhibition of 1851. In the glittering Crystal Palace, Britain displayed to the world all its industrial, scientific, and economic might, including the green tea dyes. This public exhibition marked the moment when tea, the national drink of Britain, came out of the shadows of myth and mystery and into the light of Western science and understanding. Fortune unmasked unwitting Chinese criminality and provided an irrefutable argument for British-manufactured tea.
This is an excerpt from For All the Tea in China: How England Stole the World’s Favorite Drink and Changed History by Sarah Rose.