Formaldehyde: Uses, Carcinogen Classification and SDS Requirements

Formaldehyde (CH2O, CAS 50-00-0) is a pungent, colourless gas at room temperature, and in trade it is nearly always handled as an aqueous solution called formalin, containing roughly 37 percent formaldehyde stabilised with 10 to 15 percent methanol. It is an essential industrial building block and also one of the most closely regulated chemicals, because it is a recognised human carcinogen and a skin sensitiser.

Why formaldehyde is used

• Resins: urea-formaldehyde, phenol-formaldehyde and melamine-formaldehyde resins are the binders in plywood, particleboard, MDF, laminates and insulation.
• Chemical intermediates: for making polyacetal plastics, 1,4-butanediol, pentaerythritol and many other products.
• Preservatives and disinfectants: as a biocide in some industrial fluids, and for tissue preservation in pathology and teaching laboratories.
• Textile finishing, to give crease resistance, though restricted in many markets.
• Fertilisers and agrochemicals, including slow-release nitrogen products.
• Embalming and veterinary uses in regulated settings.

Classification

The harmonised classification for formaldehyde includes carcinogenicity category 1B (H350: may cause cancer), germ cell mutagenicity category 2 (H341), acute toxicity category 3 by the oral, dermal and inhalation routes (H301, H311, H331), skin corrosion category 1B (H314) and skin sensitisation category 1 (H317). The signal word is Danger and the pictograms are corrosion (GHS05), skull and crossbones (GHS06) and health hazard (GHS08). The harmonised entry applies concentration limits, so a 37 percent formalin solution carries the full set, while a weaker solution drops some of them, and the sensitiser classification applies even at quite low percentages. Specific limits and notes in Annex VI govern every dilution.

That sensitivity to concentration is why you must classify each product separately. It is also an example of why a mixture of low-percentage formaldehyde in a cleaning or textile product can still need a hazard statement and an EUH208-type allergen note. Our mixture classification guide explains how cut-off values work.

Exposure and health

Short-term exposure irritates the eyes, nose, throat and skin; repeated exposure can cause allergic dermatitis and asthma. Long-term inhalation exposure is linked to nasopharyngeal cancer and leukaemia in occupational studies. Many countries set very low occupational exposure limits, often at or below 0.3 parts per million as a short-term limit, and require monitoring and medical surveillance for exposed workers. Your Section 8 must reflect the limit applicable in the market where you sell, and Section 11 should record the carcinogenicity classification and its basis.

Handling and storage

Use closed systems, local exhaust ventilation and suitable respiratory protection where airborne levels might exceed limits, nitrile or butyl gloves, chemical goggles and protective clothing. Store formalin in closed containers at moderate temperature, because it can polymerise to a white solid (paraformaldehyde) when stored cold, and can slowly oxidise to formic acid. Keep away from strong oxidisers, acids, bases, phenols and ammonia, with which it reacts. Methanol in the stabiliser also makes the solution flammable, so flash point should appear in Section 9.

Documents and transport

Formaldehyde solutions are transported as Class 8 corrosives with a subsidiary flammable or toxic hazard depending on methanol content and concentration. Check the current UN number and packing group. For wood products and textiles, buyers also request formaldehyde emission test results, which is a separate certificate from the SDS. You can see the harmonised data we hold on the formaldehyde page. Learn how to read toxicity numbers in our LD50 guide.