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11.2 Formaldehyde
Formaldehyde, HCHO, is a colourless chemical with a strong, pungent, irritating smell. OSHA has estimated that about 2.1 million workers are exposed to it. It is used mainly in making resins, as an intermediate in industrial chemicals such as ethylene glycol, as a bactericide or fungicide, in pressed wood manufacture, in funeral services, in pharmaceuticals, and in preserving oil well fluids. It is also a by-product of many processes, and it is in clinical samples preserved in formalin.
The hazard depends on its form and concentration. A solution of 37 to 50 percent, such as is used to preserve specimens, is far more dangerous to skin and eyes than a solution under 1 percent.
Exposure limits
| Limit | Value |
|---|---|
| Action level | 0.5 parts per million (ppm), as an eight hour time-weighted average (TWA) |
| Permissible exposure limit (PEL) | 0.75 ppm, as an eight hour TWA |
| Short term exposure limit (STEL) | 2 ppm, averaged over 15 minutes |
The TWA is the average for a normal eight hour day and 40 hour week to which nearly all workers can be exposed repeatedly without harm. The STEL must not be exceeded whatever the TWA.
Monitoring
- Initial monitoring identifies every employee who may be exposed at or above the action level or the STEL and measures their exposure. Repeat it whenever a change in production, equipment, process, personnel or controls may bring new exposure.
- Periodic monitoring is done for employees at or above the action level or the STEL. Repeat at least once a year under worst case conditions, and every six months for exposures at or above the STEL.
- Monitoring may stop if two consecutive samples, taken at least seven days apart, show exposure below the action level and the STEL, unless something changes.
Health effects
- Inhalation. At 25 to 50 ppm: tissue damage and serious respiratory injury, with sneezing, wheezing, chest tightness, headache and nausea. At 50 to 100 ppm: fluid in the lungs and severe lower airway effects. Above 100 ppm: death is possible.
- Chronic exposure. Headache, rhinitis, nausea, drowsiness, breathing problems, kidney injury and sensitisation. Neurological effects include sleep disorders, irritability, balance problems, memory loss and poor concentration. Long exposure is associated with cancer of the nose, sinuses and throat.
- Ingestion. Burning of the mouth, throat and stomach, vomiting, severe abdominal pain, headache, convulsions, unconsciousness and coma, and damage to organs. The average fatal dose is about 1 to 2 ounces of a 37 percent solution.
- Skin. Smarting, whitening, roughness, hardness and burns. In people who have been exposed before, a sensitising dermatitis with sudden blisters on the eyelids, face, neck and arms may follow. It is easily absorbed through the skin and is among the common causes of dermatitis.
- Eyes. At 0.05 to 3 ppm: redness, itching, pain, blurred vision and tearing. At 4 to 20 ppm: heavy tearing and eye damage. Solutions can cause permanent clouding of the cornea and loss of sight.
A study aid, not published or endorsed by IOSH or OSHA. Laws and limits differ between countries.