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Formaldehyde is a gas with a pungent odor that is used commonly in the processing of paper, fabrics, and wood products and for the production of urea foam insulation. Low-level formaldehyde exposure has been found in stores selling clothing treated with formaldehyde-containing crease-resistant resins, in mobile homes, and in tightly enclosed rooms built with large quantities of formaldehyde-containing products used in construction materials. Formaldehyde aqueous solution (formalin) is used in varying concentrations (usually 37%) as a disinfectant and tissue fixative. Stabilized formalin may also contain 6–15% methanol.

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  1. Mechanism of toxicity

    1. Formaldehyde causes precipitation of proteins and will cause coagulation necrosis of exposed tissue. The gas is highly water-soluble. When inhaled, it produces immediate local irritation of the upper respiratory tract and has been reported to cause spasm and edema of the larynx.

    2. Metabolism of formaldehyde produces formic acid, which may accumulate and produce metabolic acidosis if sufficient formaldehyde was ingested.

    3. Formaldehyde has been listed by the International Agency for Research on Cancer (IARC) as a known human carcinogen associated with nasal sinus and nasopharyngeal cancer. NIOSH also considers formaldehyde a carcinogen.

  2. Toxic dose

    1. Inhalation. The OSHA workplace permissible exposure limit (PEL) is 0.75 ppm (8-hour TWA). The NIOSH-recommended exposure limit (REL) is 0.016 ppm (8-hour TWA; the REL is 0.1 ppm for a 15-minute exposure). The air level considered immediately dangerous to life or health (IDLH) is 20 ppm.

    2. Ingestion of as little as 30 mL of 37% formaldehyde solution has been reported to have caused death in an adult.

  3. Clinical presentation

    1. Formaldehyde gas exposure produces irritation of the eyes, and inhalation can produce cough, wheezing, and noncardiogenic pulmonary edema.

    2. Ingestion of formaldehyde solutions may cause severe corrosive esophageal and gastric injury, depending on the concentration. Lethargy and coma have been reported. Metabolic (anion gap) acidosis may be caused by formic acid accumulation from metabolism of formaldehyde or methanol.

    3. Hemolysis has occurred when formalin was accidentally introduced into the blood through contaminated hemodialysis equipment.

  4. Diagnosis is based on a history of exposure and evidence of mucous membrane, respiratory, or GI tract irritation.

    1. Specific levels

      1. Plasma formaldehyde levels are available in plasma, but formate levels may better indicate the severity of intoxication.

      2. Methanol (See Methanol) and formate levels may be helpful in cases of intoxication by formalin solutions containing methanol.

    2. Other useful laboratory studies include arterial blood gases, electrolytes, glucose, BUN, creatinine, osmolality, and calculation of the osmole gap (See Serum osmolality and osmole gap).

  5. Treatment

    1. Emergency and supportive measures

      1. Maintain an open airway and assist ventilation if necessary (See Airway and Breathing).

      2. Inhalation. Treat bronchospasm (See Hypoxia) and pulmonary edema (See Hypoxia) if they occur. Administer supplemental oxygen and observe for at least 4–6 hours.

      3. Ingestion

        1. Treat coma (See Coma and stupor) and shock (See Hypotension) if they occur.

        2. Administer IV saline or other crystalloids to replace fluid losses caused by gastroenteritis. Avoid fluid overload in patients with inhalation exposure because of the risk for pulmonary edema.

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