Lead Toxicity & Skin
Testing Whether Lead in White Lead Makeup Passes Through The Skin
Lead has to enter the body in order to be poisonous. There are four ways lead can potentially get into the human system:
It can be eaten.
It can be inhaled as fume or vapour.
It could theoretically be injected.
It can pass through the skin.
White lead makeup would be much more toxic if the lead is in a form where it can be absorbed through the skin.
At Toxic Allure we are making 18th century white lead makeup recipes and testing how much lead is absorbed through skin. We are not testing humans or animals. We measure how much lead passes through samples of ethically sourced pigskin.
'The House of Butterflies'
Scientists do know that if lead is in the form of some organic compounds it can pass readily through the skin. For decades lead was added to gasoline in the form tetraethyl lead. This organic lead compound is very dangerous.
In the 1920s, workers at tetraethyl lead plants in the United States died. Hundreds of workers suffered psychosis. Workers hallucinated insects crawling up their arms. The conditions in one factory were so awful was called 'The House of Butterflies' because many workers were waving off and dusting off imaginary bugs.
We know surprisingly little!
There have been very few scientific studies which have tested the absorption of lead compounds through the skin.
There were experiments in the 1930s and 1940s which showed tetraethyl lead was dangerous. There are two or three published studies which show that some organic lead compounds are absorbed much more than a few inorganic compounds.
However, in total, less than 10 lead compounds have had their skin absorption properties tested.
How We Test
This is the system we use to directly measure how much lead passes through the skin:
We place a piece of pigskin on top of a flask containing saline. The saline is water with salt added to match the level in human body fluids. We then place known amounts of makeup on top of the pigskin. We let the makeup sit on the skin for a few hours while we keep everything at body temperature. At the end of the experiment, we take the saline out of the flask and measure how much lead it contains.
From this we know how much lead passed through a small area of skin in a known amount of time. We can then calculate the amount of lead that would be absorbed if a woman painted her whole face and left the makeup on for a few hours.
The Franz Cell
The system that tests how much lead passes through the skin is called a Franz Cell.
Pigskin is clamped in place between a bottom flask and a small upper chamber. You can see this in the photo on the right. We pipette or spread the makeup on the skin in the upper chamber. We collect the saline from the bottom flask at the end of an experiment, and send it to a specialty lab in Toronto for lead testing.
Franz cells are commonly used to test the absorption of pharmaceuticals through the skin. They are also used to test cosmetics. We are using a methodology very similar to that described in a European Union cosmetic testing policy document.
Our skin is an amazing organ. It protects us from chemicals, germs and UV exposure. It also helps regulate our body temperature. We think of it as a simple layer, but it is actually a very complex structure. There are a lot of layers for a lead compound to get through before it reaches a part of the body where it can be picked up by body fluid.
The absorption of lead from a makeup is challenging to understand. Different kinds of chemicals can get through the different layers more or less easily. We need to understand what form the lead is in, to understand whether it can be absorbed.
In addition, 18th century makeup is a mixture of chemicals which include oils, fruit acids and minerals. Some of those compounds can change the absorption properties of skin. Their presence or absence in the mixture can alter how much of a specific lead compound can enter the body.