Is formaldehyde another type of formalin?
No, formalin is another type of formaldehyde. Formaldehyde is a very irritant gas just like many of the other aldehydes. Its water solution is known as formalin. As long as cadavers were widely used for teaching anatomy, medical students stank of formalin; formalin is a highly effective preservative and used to embalm corpses.
Formaldehyde reacts with many other substances, and therefore it is used in glues and other construction materials to harden (polymerize) other materials. It is also used as a preservative in many products, e.g. in cosmetics. It is oxidized rather rapidly in air to carbon dioxide in a reaction catalyzed by light. In the organism, it is oxidized to formic acid and further to carbon dioxide. Formaldehyde is even a normal product of metabolism in humans, and there is a relatively high natural formaldehyde concentration found in the body.
The outdoor sources of formaldehyde relate to traffic-related photochemical air pollution in conjunction with other aldehydes such as acrolein. The indoor sources evoking the highest exposures are urea-formaldehyde glues which are used in boards, parquet floors, plastic coverings and furniture softened by moisture and warmth. Improperly installed urea-formaldehyde foam insulation may also release formaldehyde.
Other indoor sources may be water-based paints, formaldehyde releasing textiles, cleaning agents, disinfectants, felt tip pens, gas stoves and fireplaces. Many chipboard materials used to release high formaldehyde concentrations to the indoor air immediately after construction. Smoking is also an important indoor source. Thus we are surrounded by many potential sources of this nasty chemical.
In terms of human exposure, formaldehyde absorbed via respiration is in third place, behind carbon monoxide coming mostly from outdoors, and the rather innocuous acetone which originates mainly from indoor sources. If there are no specific indoor sources, then the exposure levels are around 10 μg/m3. If there are indoor sources then this can easily increase to 40–100 μg/m3. This level can be detected by sensitive people by its odour, and higher concentrations even cause irritation of mucous membranes. In some instances, the levels in factories have been even 100–10,000 μg/m3.
Formaldehyde is a primary irritant causing irritation of the mucous membranes of eyes, nose and upper respiratory tract. The level causing irritation is low – about 100 μg/m3 in adults and 40 μg/m3 in children. Very high concentrations may cause nasal cancer and possibly leukaemia. This became evident from occupational studies, because some workers were exposed for decades to extremely high concentrations of formaldehyde.
Should something be done?
The risks of indoor formaldehyde have been studied quite actively since the 1980s, and today the release from construction materials is restricted, e.g. chipboard no longer releases large amounts. Nonetheless, concentrations exceeding odour or irritant threshold are not uncommon. For the general population, in addition to avoiding poor materials, the most important action is to ventilate new homes effectively during the first months after their construction or after a major repair. Ventilation is important also when handling glues and paints releasing formaldehyde.
Formaldehyde is an irritant gas and its concentrations should be kept as low as possible. The most important sources are indoor sources, and effective ventilation is a good way to avoid problems as is selection of quality materials.
One level up: The air that we breathe
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