What makes some hand sanitizers dangerously toxic?

TeachableMedicalNews article 08282020

Teachable moment in classrooms:

1. chemical basis of life chapter – adenosine triphosphate (ATP)
2. cellular basis of life chapter –sites of detoxification inside the cell
3. cellular basis of life chapter – mitochondria as site of ATP production
4. digestive system chapter – absorption through stomach mucosa
5. metabolism chapter – electron transport chain as most efficient ATP producing process inside mitochondria
6. special senses chapter – gross anatomy of optic nerve

The news item:  A recent news item described over a hundred hand sanitizer brands are being removed from store shelves because they may be dangerously toxic:

FDA says to avoid these 130 hand sanitizer products that may not work, or are toxic

Regulators say some of the products contain dangerous levels of methanol, which can lead to blindness, hospitalization and even death.

The article mentions that the toxic ingredient is methanol, and that it may cause blindness.

So, Why Do I Care??  Poisoning by methanol, also called wood alcohol, sickens over 20,000 people each year in the US.  These people may become blind in 24 hours, and suffer long-lasting damage to their kidneys and brain. The best prevention is not to consume methanol either by drinking or through contact with skin, such as through hand sanitizers.  So, taking hand sanitizers off the shelf is part of the prevention.

Plain English, Please!!! First, let’s talk about what methanol is. Methanol is chemically similar to ethanol, the alcohol in adult beverages. Methanol gets into hand sanitizers when the ethanol ingredient is contaminated with methanol. When ethanol is made by distilleries, sometimes inadvertently methanol is distilled into the product, so then it becomes part of the hand sanitizer.

Second, let’s talk about how methanol causes damage so quickly. Normally our cells chemically change, detoxify, harmful chemicals into harmless ones.  In the case of methanol, however, the end result of detoxification is yet another toxic chemical called formic acid. This acid enters into mitochondria and disables a molecule that is part of the most efficient ATP production line, the electron transport chain. The result is that mitochondria slow their production of ATP, and the lack of ATP disables cells in the kidney and the brain causing organ malfunctions.

Third, let’s talk about why methanol causes blindness. The visual signals from the eye are carried to the brain by the optic nerve. The optic nerve is a bundle of a million axons, the long extensions of neurons. Because axons carry nerve signals, the optic nerve is a million-lane highway for nerve signals for our vision. Just as lane restrictions slow highway traffic, damage to the neurons in the optic nerve will slow the traffic of visual nerve signals to the brain. Neurons in the optic nerve has an especially high need for ATP, so when ATP production is low in methanol poisoning, many of the neurons die and their axons fall apart to start the lane restrictions. More lane restrictions happen when the debris of dead neurons attracts the cells of the immune system and the high activity of those white blood cells damage more neurons. Another round of lane restrictions happen when the swelling from the inflammation blocks blood flow to the optic nerve, and even more neurons die. When you add it all up, methanol poisoning slows the flow of visual information traffic to a trickle, and visual impairment and blindness is the result.