CHILDREN WERE POISONED BY THEIR SHOES
Aniline dyes absorbed by skin impaired blood’s ability to deliver oxygen to tissues
“Mummy, everything is spinning,” complained the little French girl, soon echoed by her brothers and sisters. The worried parents, further alarmed by the children’s lips having taken on a blue hue, consulted physicians who immediately turned their attention to what the affected youngsters had in common. As it turned out, they were all wearing shoes that had been recently dyed. The intriguing case was duly reported in the July 17, 1900 issue of the “Bulletin de l’Académie de médicine,” with the title “A case of poisoning by yellow shoes blackened with aniline.”
Although they didn’t know it at the time, the doctors were describing “methemoglobinemia,” a condition in which the blood’s ability to deliver oxygen to tissues is impaired. Normally, after being absorbed into the bloodstream from the lungs, oxygen is transported around the system by hemoglobin, a complex molecule that contains an iron ion capable of binding oxygen. Under certain conditions this “ferrous” ion can lose an electron, converting to a “ferric” state that is incapable of binding oxygen. This altered form of hemoglobin is known as methemoglobin.
Nitrates as found in cured meats, leafy green vegetables and in water contaminated with fertilizer constitute classic examples of substances that can steal an electron from ferrous iron. Aniline dyes are also capable of such thievery. These chemicals were first synthesized in the middle of the 19th century and quickly achieved great popularity due to the wide range of colours they were capable of delivering. But they delivered something else as well. Met hemoglobin em ia!
If aniline dyes are absorbed through the skin, they are eventually metabolized in the liver yielding phenyl hydroxyl a mine as one of the products. This can oxidize ferrous iron to ferric, with the result being cyanosis, the bluish discoloration of the skin and mucous membranes, typical of met hemoglobin em ia.
This is just what happened to the unfortunate children who were poisoned by their shoes! It seems after the application of the dye, the shoes had not been
Drs. Landouzy and Brouardel … went on to prove the danger of absorbed aniline dyes by applying wet dye to the skin of a rabbit.
allowed to dry properly, and aided by moisture, the dye ended up being absorbed through the skin. Drs. Landouzy and Brouardel, who had written the original case report about the poisonous shoes, went on to prove the danger of absorbed aniline dyes by applying wet dye to the skin of a rabbit. The animal died within a couple of hours, with its mucous membranes tinged blue.
Refurbishing shoes and boots that had been repeatedly sullied by walking on unpaved, muddy streets pockmarked with horse excrement was a challenge. For men, this often meant using aniline dyes to “blacken” the stained footwear. That practice led to a number of poisonings more serious than that of the French children, all of whom recovered. The difference was exposure to nitrobenzene, a solvent used in the blacking process.
Back in 1832 German chemist Eilhard Mitscherlich had first synthesized nitrobenzene by reacting benzene with nitric acid. He noted that it had a pleasant almond-like smell that led to its eventual use in perfumery as “Oil of Mirbane.” Because of its ability to dissolve organic compounds, nitrobenzene became a popular cheap solvent for dyes, as well as a staple in the drycleaning industry.
Unfortunately, it is even more adept than aniline at converting hemoglobin to methemoglobin. Besides being involved in the toxic shoe capers, nitrobenzene caused a number of fatalities among workers who were occupationally exposed.
Today, consumers are unlikely to encounter nitrobenzene, but the chemical is widely used in industry as the starting material for the production of aniline. Aside from dye production, aniline is in great demand thanks to its role in the synthesis of polyurethanes, a class of polymers with application in products ranging from foam pillows and adhesives to skateboard wheels and Spandex fibres.
Before the introduction of the aniline dyes, shoes were commonly “blackened” with a paste of beeswax or beef tallow coloured with “lampblack,” the soot from oil lamps.
This was actually a safer product than the aniline dyes and resembled the shoe polishes used today. Current products are formulated with carbon black or synthetic dyes in a base of waxes such as lanolin from sheep’s wool or carnauba from the leaves of a type of palm tree and are thickened with gum arabic from the acacia tree.
The components are blended to a smooth consistency with naphtha, a volatile mixture of hydrocarbons from petroleum. Polish should be applied with gloves in a well-ventilated area.
It is unlikely that nitrobenzene is used as a solvent in shoe polish these days, but that cannot be known for sure since a list of ingredients for such products is not required. At one time, nitrobenzene was indeed used due to its excellent solvent properties and its ability to impart a pleasant smell.
I do like to provide a public service, but I will refrain from going around sniffing various shoe polishes to see if I detect the smell of almonds.