What happens to your body with long-term exposure to acetonitrile and methanol?

**Author: Original from Internet**

Acetonitrile (CH₃CN) and methanol (CH₃OH)—their names may sound quite technical, but they’re used almost every day in the lab: for preparing mobile phases, rinsing syringes, and performing derivatization reactions. But what happens to the body if you’re exposed to them over a long period of time?

These two substances share a few common features: they are both liquids, they both have a distinct odour, and they can easily enter the body via the respiratory tract and skin. They can be absorbed into the body through the respiratory tract, the digestive tract and the skin. However, their mechanisms of toxicity are entirely different, and the target organs they affect are also distinct.

Acetonitrile, also known as methyl cyanide, contains a cyano group (-CN) in its molecule. Once inside the body, acetonitrile is metabolised to release cyanide, which interferes with cellular respiration. Specifically, after entering the body, acetonitrile is metabolised by the liver, first converting into hydroxyacetonitrile, and then breaking down into formaldehyde and hydrogen cyanide.

Furthermore, acetonitrile poisoning has a distinctive characteristic: its slow onset. Unlike the acute poisoning caused by hydrogen cyanide, which can lead to collapse within minutes, the latency period for acetonitrile poisoning is generally 4 to 12 hours. Exposure to 160 ppm for 4 hours results in mild facial flushing in half of the subjects.

Symptoms include weakness, nausea and vomiting, chest tightness and pain; in severe cases, blood pressure drops, convulsions and coma may occur, and it may also cause kidney damage such as proteinuria. In other words, if you accidentally inhale too much this morning, you may not feel unwell until this afternoon or even this evening – by the time you start to feel unwell, your body will have already been poisoned for several hours.

Methanol itself is not particularly toxic; what is truly dangerous is the metabolite it produces within the body.

Under the action of alcohol dehydrogenase in the liver, methanol is first converted into formaldehyde, and then into formic acid. Formic acid cannot be further metabolised by the body and gradually accumulates, causing severe damage to the optic nerve and potentially leading to blindness or even death. Formaldehyde is 33 times more toxic than methanol and rapidly destroys cellular structures; formic acid, meanwhile, inhibits the cellular respiratory chain, leading to tissue hypoxia, with the most significant damage occurring to the optic nerve and retina.

A single instance of heavy exposure constitutes acute poisoning, but what most laboratory technicians are more concerned about is the chronic damage caused by ‘handling a little every day and inhaling a little every day. The nervous system, liver and skin—both solvents are taking their toll on your health.

What is even more concerning is that health risks increase significantly in occupational settings where ventilation is poor or where there is direct contact with high concentrations of solvents. The synergistic effects of using acetonitrile and methanol together may exacerbate toxicity, so particular caution is required.

In practice, laboratory technicians are frequently exposed to both solvents simultaneously—for example, methanol and acetonitrile are present together in the mobile phase of liquid chromatography, and the two are used alternately when cleaning needles—resulting in cumulative harm to the body.

All operations involving methanol or acetonitrile must be carried out within a fume cupboard. Lower the glass sash of the fume cupboard as far as possible; do not put your head inside the fume cupboard. Where conditions permit, the waste liquid tube from the liquid chromatograph should be connected directly to a waste container and sealed as tightly as possible; the waste container should be placed inside the fume cupboard.

Common laboratory gloves include latex, nitrile, PVC and neoprene gloves. Nitrile gloves are the first choice for handling organic solvents: they provide excellent protection against a wide range of organic solvents, and their chemical resistance is generally superior to that of latex and PVC.

Under no circumstances should PVC gloves be used—PVC gloves offer no protection against organic substances such as solvents. Many solvents cause the plasticisers in the gloves to leach out, which not only causes contamination but also significantly reduces the gloves’ barrier function.

Gloves handling details: Check the gloves (especially the finger seams) for any tears; avoid touching shared items during the experiment; wash your hands immediately after removing the gloves; replace gloves immediately if they become contaminated with solvents.

In standard laboratory settings, a fume cupboard combined with nitrile gloves is generally sufficient to prevent most exposure. However, if ventilation is poor, or if you need to handle large quantities of solvents for a short period or deal with a spill, you should wear a gas mask or half-mask respirator designed to protect against organic vapours.

Wear safety goggles or use a fume cupboard sash when preparing solvents. If a solvent splashes into the eyes, immediately rinse with copious amounts of water from an eye wash station for at least 15 minutes, lifting the eyelids to ensure thorough rinsing, and seek medical attention immediately.

Wear long-sleeved cotton laboratory coats; do not enter the laboratory wearing sandals or shorts. If solvent comes into contact with clothing, remove the contaminated garments immediately and rinse them with water. Make it a habit to wash your hands and face after completing experiments; under no circumstances should methanol or acetonitrile be used to wash hands.