Acetaldehyde which is a metabolite of ethanol and  is also carcinogenic to humans.

It is a colorless liquid or gas, boiling near room temperature. 

It is an aldehydes, occurring widely in nature and being produced on a large scale in industry. 

Acetaldehyde occurs naturally in coffee, bread, and ripe fruit, and is produced by plants. 

Acetaldehyde is also produced by the partial oxidation of ethanol by the liver enzyme alcohol dehydrogenase and is a contributing cause of hangover after alcohol consumption. 

Acetaldehyde is a byproduct of ethanol breakdown in the liver, metabolized by Alcohol dehydrogenase (ADH), Cytochrome P-450 and bacterial catalases.

The liver then normally eliminates 99% of the acetaldehyde. 

Those with ADH1B*1 have higher rates of conversion of ethanol into Acetaldehyde while, people with ALDH2*2 have a slower conversion rate of acetaldehyde to acetate causing faster build up of acetaldehyde concentrations.    

Acetaldehyde is a colorless, flammable substance with a pungent odor that is a common environmental pollutant and a toxic substance to humans. 

It is also produced naturally in the human body as a by-product of alcohol metabolism. 

Acetaldehyde exposure pathways include air, water, land, or groundwater, as well as drink and smoke.

Consumption of disulfiram inhibits acetaldehyde dehydrogenase, the enzyme responsible for the metabolism of acetaldehyde, thereby causing it to build up in the body.

The International Agency for Research on Cancer (IARC) has listed acetaldehyde as a Group 1 carcinogen.

Acetaldehyde is one of the most frequently found air toxins with cancer risk greater than one in a million.

Acetaldehyde is a precursor to vinylphosphonic acid, which is used to make adhesives and ion conductive membranes.

In the liver, the enzyme alcohol dehydrogenase oxidizes ethanol into acetaldehyde, which is then further oxidized into harmless acetic acid by acetaldehyde dehydrogenase. 

In the brain, the enzyme catalase is primarily responsible for oxidizing ethanol to acetaldehyde, and alcohol dehydrogenase plays a minor role.

Acetaldehyde was mainly used as a precursor to acetic acid, but is produced more efficiently from methanol.

The global market for acetaldehyde is declining. 

Acetaldehyde is an irritant of the skin, eyes, mucous membranes, throat, and respiratory tract. 

Symptoms of exposure to this compound include nausea, vomiting, and headache. 

The perception threshold for acetaldehyde in air is in the range between 0.07 and 0.25 ppm.

At such concentrations, the fruity odor of acetaldehyde is apparent. 

Conjunctival irritations have been observed after exposure.

Acetaldehyde is carcinogenic in humans.

There is evidence for the carcinogenicity of acetaldehyde, the major metabolite of ethanol.

Acetaldehyde is damaging to DNA and causes abnormal muscle development as it binds to proteins.

Acetaldehyde induces DNA interstrand crosslinks, a form of DNA damage. 

These DNA crosslinks can be repaired by either of two replication-coupled DNA repair pathways.

People with a genetic deficiency for the enzyme responsible for the conversion of acetaldehyde into acetic acid may have a greater risk of Alzheimer’s disease. 

A study of heavy drinkers found that those exposed to more acetaldehyde than normal through a genetic variant of the gene encoding for alcohol dehydrogenase are at greater risk of developing cancers of the upper gastrointestinal tract and liver.

The drug disulfiram inhibits acetaldehyde dehydrogenase, an enzyme that oxidizes the compound into acetic acid. 

With the enzyme inhibited, acetaldehyde accumulates, and If one consumes ethanol while taking disulfiram, the hangover effect of ethanol is felt more rapidly and intensely. 

Disulfiram is sometimes used as a deterrent for alcoholics wishing to stay sober.

Acetaldehyde is a potential contaminant in workplace, indoors, and ambient environments. 

The mean indoor concentration of acetaldehydes measured is approximately seven times higher than the outside acetaldehyde concentration. 

Volatile organic compounds such as benzene, formaldehyde, acetaldehyde, toluene, and xylenes have to be considered priority pollutants with respect to their health effects. 

In renovated or completely new buildings, the volatile organic compounds concentration levels are often several orders of magnitude higher than in existing structures.

The main sources of acetaldehydes in homes include building materials, laminate, PVC flooring, varnished wood flooring, and varnished cork/pine flooring found in the varnish, in plastics, oil-based and water-based paints, in composite wood ceilings, particle-board, plywood, treated pine wood, and laminated chipboard furniture.

The use of acetaldehyde is widespread in different industries, and it may be released into waste water or the air during production, use, transportation and storage. 

Acetaldehyde sources include fuel combustion emissions from internal combustion engines and power plants that burn fossil fuels, wood, or trash, oil and gas extraction, refineries, cement kilns, lumber and wood mills and paper mills.

Acetaldehyde is also present in automobile and diesel exhaust.

As a result, acetaldehyde is one of the most frequently found air toxics with cancer risk greater than one in a million.

Natural tobacco polysaccharides make acetaldehyde a significant constituent of tobacco smoke.

Acetaldehyde is also the most abundant carcinogen in tobacco smoke; it is dissolved into the saliva while smoking.

Acetaldehyde has been found in cannabis smoke.

Many microbes produce acetaldehyde from ethanol, but they have a lower capacity to eliminate the acetaldehyde, which can lead to the accumulation of acetaldehyde in saliva, stomach acid, and intestinal contents. 

Fermented food and many alcoholic beverages can also contain significant amounts of acetaldehyde. 

Acetaldehyde, derived from mucosal or microbial oxidation of ethanol, tobacco smoke, and diet may be an accumulative carcinogen in the upper digestive tract.

According to European Commission’s Scientific Committee on Consumer Safety’s (SCCS) “Opinion on Acetaldehyde” (2012) 

The European Commission’s Scientific Committee on Consumer Safety’s cosmetic products special risk limit is 5 mg/L and acetaldehyde should not be used in mouth-washing products.

Acetaldehyde is considered a toxic substance at high concentrations.

It can cause damage to tissues and organs, leading to adverse health effects. 

Prolonged exposure to elevated levels of acetaldehyde can result in cellular damage and oxidative stress.

Acetaldehyde is responsible for many of the immediate effects experienced after alcohol consumption. 

It contributes to symptoms such as facial flushing, increased heart rate, nausea, and headache. 

It is also a key factor in the development of alcohol-related disorders, including alcohol use disorder and alcohol-related liver diseases.

Acetaldehyde has been classified as a Group 1 carcinogen by the International Agency for Research on Cancer (IARC). 

Prolonged exposure to acetaldehyde, particularly in the context of alcohol consumption, has been linked to an increased risk of developing certain types of cancer, such as cancers of the oral cavity, pharynx, esophagus, and liver.

Some individuals may experience adverse reactions to acetaldehyde, particularly those with genetic variations in enzymes involved in its metabolism. 

These reactions can include facial flushing, rapid heart rate, headache.

Adverse symptoms commonly known as “alcohol flush reaction” or “Asian flush”, can occur .

Acetaldehyde is also present in the environment as a pollutant. 

It is emitted by industries, vehicles, and various combustion processes. 

Chronic exposure to high levels of acetaldehyde in the air has been associated with respiratory problems, eye irritation, and other negative health effects.

Acetaldehyde is typically quickly metabolized and converted to less harmful substances in the body. 

Heavy alcohol consumption, liver dysfunction, or excessive exposure to acetaldehyde can result in a buildup of this compound and increases associated health risks.

 Acetaldehyde has an exceedingly low taste/odor threshold of around 20–40 ppb and can cause an off-taste in bottled water.

The level at which one could detect acetaldehyde is still considerably lower than any toxicity.

Candida albicans in patients with potentially carcinogenic oral diseases has been shown to produce acetaldehyde in quantities sufficient to cause toxicity.

The health hazards associated with acetaldehyde exposure include:

1. Carcinogenicity: Acetaldehyde is  classified by the International Agency for Research on Cancer (IARC) as a Group 1 carcinogen.

It causes cancer in humans: cancer of the upper respiratory tract, esophagus, and liver.

As a respiratory irritant:] it can can irritate the eyes, nose, throat, and lungs causing respiratory symptoms like cough and respiratory distress.

Prolonged exposure to acetaldehyde can result in neurological symptoms like headache, lightheadedness, dizziness, and confusion.

Acetaldehyde can cause liver damage and alcohol-induced liver diseases like cirrhosis.

Acetaldehyde can cause reproductive toxicity like testicular damage and decreased sperm count and motility in males.

Acetaldehyde can be cause skin irritation, allergic contact dermatitis and photoallergic reactions.


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