Formaldehyde

Formaldehyde or methanal is a chemical compound, more specifically an aldehyde (the simplest of them), highly volatile and highly flammable, with the formula H2C=O. It is obtained by catalytic oxidation of the methyl alcohol. Under normal conditions of pressure and temperature it is a colorless gas, with a penetrating odor, very soluble in water and in esters. ~40% aqueous solutions are known as formalin, which is a colorless liquid with a pungent and suffocating odor; these solutions may contain methyl alcohol as a stabilizer. It can be compressed to the liquid state; its boiling point is -19 °C.

It has many names (see main table); Its traditional name comes from formica, the Latin word for "ant"; its name according to the IUPAC systematic nomenclature is methanal.

History

Although formaldehyde was first described in 1859 by the Russian chemist Aleksandr Butlerov (1828–86), where he called it "Dioxymethylene" (methylene dioxide) due to an error in his formula (C₄H₄O₄). It was not until 1869 that August Wilhelm von Hofmann correctly identified it.

Reactions

Formaldehyde is dissolved in water (400 ml gas /L of water at 20 °C). The solution slowly breaks down to form paraformaldehyde, the polymer of formaldehyde. The cyclic trimer can also be formed. The oxidation of formaldehyde produces formic acid and, in a second stage, water and carbon dioxide.

Summary

The industrial synthesis of methanal is based on the semipartial oxidation of methanol (H₃COH) over solid catalysts (metal oxides; usually a mixture of iron oxide, molybdenum and vanadium) or the conversion of methanol to elemental hydrogen and formaldehyde in the presence of elemental silver.

Small amounts of formaldehyde are also released in the incomplete combustion of various organic materials as well as some inorganic materials such as plastics and polymers. Thus, significant concentrations are found, for example, in tobacco smoke.

Applications

Formaldehyde is one of the most important basic organic compounds in the chemical industry. The Spanish group ERCROS has a production capacity of 788,000 t per year and BASF 500,000 t per year.< sup>[citation required] It is used in the production of various products, from medicines to melamine, bakelite, etc.

In the past, a 35% formaldehyde solution in water was used as a disinfectant. It is currently used for the preservation of biological samples and fresh carcasses, generally in a 5% dilution in water.

In histotechnology, it is used neutralized or buffered at pH 7.0 at 10%, thus avoiding the precipitation and formation of formol crystals in the tissues. Buffered formalin is the standard fixative used for immunohistochemistry or in situ hybridization techniques. It is also used in fixative mixtures in conjunction with other agents (alcohol, picric acid, acetic acid, among others), depending on the subsequent study to be performed in the biopsy. It should be noted that formaldehyde to be used in medicine must be stabilized with methanol, and kept at temperatures that do not exceed 300 degrees, since the autoignition process begins at that temperature. In addition, formaldehyde for the preservation of fatty tissues, such as the brain, is not worked at 10% but at 40%.

It is mostly used in funeral services to preserve corpses in order to place them in coffins where their remains will be watched over.

Another use is the manufacture of wrinkle-free or dewrinkled textiles. In these, the free methane content could reach up to 2% of the total weight of the textile, as it is in most cases. Currently the content has been lowered and if it exceeds 0.15% this must be declared on the label with the recommendation to wash the garment before using it, due to its great toxicity when combined with free negatively ionized atoms in the environment under normal pressure conditions. and temperature.

It is still used as a preservative in the formulation of some cosmetics and personal hygiene products such as shampoos, bath creams and iodic salts for feminine intimate hygiene. It is also being used in permanent straightening, but its use in these products has already been banned in some countries due to the high risk to the health of those who regularly work with them.

It is important to note that the International Agency for Research on Cancer in its latest reports has classified it in group 1, Confirmed Carcinogen for Humans (nasopharyngeal cancer).

Food adulteration

Both the 2005 food scare in Indonesia and the 2007 food scare in Vietnam have erupted in scandals over adding formaldehyde to food to extend its shelf life. In 2011, after a four-year absence, Indonesian authorities found food containing formaldehyde being sold in markets in various regions of the country. As of August 2011, at least two Carrefour supermarkets, the Central Jakarta Central Subdepartment of Livestock and Fisheries from Jakarta found the popular cendol containing 10 parts per million formaldehyde. In 2014, the owner of two noodle factories in Bogor, Indonesia was arrested for using formaldehyde in noodles. 50 kg of formaldehyde was seized. Food known to be contaminated included noodles, salted fish, and tofu. The chicken and beer were also rumored to be contaminated. In some places, such as China, manufacturers continue to illegally use formaldehyde as a preservative in food, exposing people to formaldehyde ingestion. In humans, formaldehyde ingestion has been shown to cause vomiting, pain abdominal pain, dizziness and, in extreme cases, can cause death. Formaldehyde analysis is performed on blood and/or urine by gas chromatography-mass spectrometry. Other methods include infrared detection, gas detector tubes, etc., of which High Performance Liquid Chromatography is the most sensitive method. In the early 20th century, American dairies frequently added it to bottles. of milk as a method of pasteurization due to a lack of knowledge and concern regarding the toxicity of formaldehyde.

In 2011, in Nakhon Ratchasima, Thailand, truckloads of rotten chickens were treated with formaldehyde for sale involving "a huge network," including 11 slaughterhouses run by a criminal gang. In 2012, 1 billion rupiah (nearly $100,000) of fish imported from Pakistan to Batam, Indonesia was found to contain formaldehyde.

In Bangladesh, there have been reports of formaldehyde contamination of food, as shops and supermarkets sell fruits, fish and vegetables that have been treated with formaldehyde to keep them fresh. However, in 2015, a Formaldehyde Control Bill in the Bangladeshi Parliament with a provision of life imprisonment as the maximum penalty, as well as a maximum fine of BTA 2,000,000, but not less than BTA 500,000 for importing, producing or hoarding unlicensed formaldehyde.

Formaldehyde was one of the chemicals used in industrialized food production in the 19th century that was investigated by the Dr. Harvey W. Wiley with his famous "Venom Squad" as part of the United States Department of Agriculture. This led to the Pure Food and Drug Act of 1906, a milestone in the early history of food regulation in the United States.

Toxicity

Exposure to formaldehyde

Formaldehyde in the environment originates from both natural sources and human activities, but is primarily produced by the combustion of materials.

Generally, more formaldehyde is found indoors than outdoors, since many household products emit formaldehyde into the environment, such as: latex paint, nail polish, plywood...

Formaldehyde poisoning can occur through various routes: inhalation (mainly), skin, eyes, and ingestion.

Formaldehyde is rapidly absorbed through the nose, upper respiratory tract, and when swallowed; instead, only small amounts are absorbed through the skin.

Once inside the body, formaldehyde is rapidly broken down to formate (which is excreted in urine) or carbon dioxide (which is excreted through the breath).

Occupational exposure limits

VLA-EC (Environmental Limit Value for Short Term Exposure): 0.6 ppm; 0.74mg/m³. VLA-ED (Environmental Limit Value for Daily Exposure): 0.3 ppm; 0.37mg/m³. These values must not be exceeded at any time.

Symptoms

• In case of inhalation: there is a sensation of burning, coughing, headache, nausea and/or jade. It severely irritates the respiratory tract, which may cause pulmonary edema (the symptoms of pulmonary edema do not manifest, often, until after a few hours and are aggravated by physical effort).

• In case of skin contact: it causes irritation.
• In case of eye contact: it is tear, it can produce blurred vision, pain and/or redness.
• In case of ingestion: drinking high amounts can cause acute pain, vomiting, coma and possibly death. The doctor should be consulted in all cases.

The effects of prolonged or repeated exposure to formaldehyde may increase the risk of cancer in humans.

Prevention of possible poisoning

• Through inhalation: ventilation, localized extraction or respiratory protection.
• Through skin contact: use insulating gloves.
• Through eye contact: adjusted safety glasses or eye protection combined with respiratory protection.
• Through ingestion: not eating, drinking, or smoking during work.

Measures to take in case of poisoning

• In case of inhalation: it is recommended to breathe clean air and keep rest, in addition to adopting a semi-incorporation position. If indicated, it would be advisable to apply artificial breathing. Medical assistance should be provided.
• In case of contact with the skin: the contaminated clothes will be removed. Then you need to clear the skin with abundant water or shower. It is indicated to provide medical assistance.
• In case of eye contact: it is convenient to rinse with abundant water for several minutes (removing contact lenses if it can be done easily). Medical assistance is then provided.