What many people may not know is that
our own bodies produce and use formaldehyde as a part of our normal metabolism (Final Report on Carcinogens Background Document for Formaldehyde [PDF], 2010). When we are exposed to methanol (e.g., via inhalation or ingestion of foods like citric fruits and juices, vegetables or fermented beverages), our bodies break it down into formaldehyde and other byproducts. Our bodies produce formaldehyde as a result of DNA demethylation (an important process for controlling gene expression, e.g., in developing embryos) and other biological processes. It is such a regular part of human metabolism, that our normal, naturally produced blood concentrations are generally about 2-3μg of formaldehyde per gram of blood (or about 2.12-3.18μg/mL)*. And it is actually a pretty important chemical; our bodies use formaldehyde to form DNA and amino acids (Toxicological Profile for Formaldehyde [PDF], ATSDR, 1999).
Role in Metabolism
Formaldehyde plays an essential role in our metabolism. As part of the metabolic process, formaldehyde, whether from an external source or produced by our bodies, is converted into formate (PDF) by the enzyme formaldehyde dehydrogenase. The resulting formate can then be eliminated in the urine, further broken down into CO2 and exhaled, or used by our cell machinery to synthesize nucleotides and nucleobases, such as purines and thymidine.
Purines include two of the four basic building blocks of DNA: adenine and guanine.
When formaldehyde is converted into formate, the body can then use it to synthesize these basic building blocks of life.
Likewise, thymidine, also called deoxythymidine, is integral to life. It is a nucleoside, which is a class of compounds that are components of nucleic acids; in other words, you need thymidine to make the nucleic acid thymine. They also perform a lot of other important functions. Nucleosides mediate hormone signaling and play a role in blood pressure and energy transfer, among other things (Jucker, 1993). Formaldehyde provides your body with the compounds necessary to synthesize thymidine. Just like with purines, if your body stopped using formaldehyde to make these basic compounds, well, all of your worries would disappear, since you'd be dead.
Even before the advent of industrial uses of formaldehyde, humans, as with every other animal on Earth, had been exposed to formaldehyde through the foods they ate, the environments in which they lived and their own metabolic processes. They developed the means to use the chemical for their own cellular function,
as well as the ability to get rid of excess amounts that would otherwise be toxic.
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