Formaldehyde · Canairy

What it is

Formaldehyde (chemical formula HCHO, also written CH2O) is a colorless gas with a sharp pungent odor most people can smell at around 0.5 to 1 part per million (ppm). It is a volatile organic compound (VOC) and one of the most common indoor air contaminants. The body itself produces small amounts as a normal metabolic byproduct, but inhaling formaldehyde from outside sources adds to that load and irritates tissue at much lower concentrations than most VOCs.

Where it comes from

Indoor sources dominate formaldehyde exposure:

Pressed-wood products (particleboard, MDF, hardwood plywood) made with urea-formaldehyde resins, used in cabinets, furniture, shelves, and subflooring
Laminate and engineered wood flooring
New carpets, drapes, and upholstery
Permanent-press fabrics and older urea-formaldehyde foam insulation
Combustion: gas stoves, unvented gas or kerosene heaters, tobacco smoke, candles, incense, wood smoke
Some cleaning products, cosmetics, and personal care products

Outdoor formaldehyde forms when sunlight reacts with other VOCs and is emitted by vehicle exhaust and industrial sources. Off-gassing from new materials peaks in the first weeks, then declines over a year or more. Heat and humidity accelerate release; a hot new mobile home can have especially high levels.

Health effects

Acute exposure causes eye, nose, and throat irritation, coughing, wheezing, and headaches starting around 0.1 ppm in sensitive people and 0.5 to 1 ppm in most people. People with asthma may have attacks triggered at low concentrations.

IARC classifies formaldehyde as Group 1, carcinogenic to humans, based on evidence for nasopharyngeal cancer and myeloid leukemia (especially in occupations with long-term exposure such as embalmers, anatomy lab workers, and industrial users). EPA's Integrated Risk Information System reached the same conclusion in 2022. Long-term exposure is also linked to chronic respiratory symptoms and reduced lung function in children.

How it's measured and typical levels

Formaldehyde is measured in parts per million (ppm) or parts per billion (ppb), or in micrograms per cubic meter. Typical levels:

Outdoor air: 1 to 5 ppb (1.2 to 6 micrograms per cubic meter)
Older established homes: 10 to 30 ppb
New manufactured homes or homes with new pressed-wood furniture: 50 to 300 ppb, occasionally higher
Heavily affected post-Katrina FEMA trailers (2006): some over 500 ppb

Exposure limits and guidelines:

OSHA PEL: 0.75 ppm (750 ppb) 8-hour time-weighted average; short-term limit 2 ppm (15-minute)
NIOSH REL: 0.016 ppm (16 ppb) TWA, ceiling 0.1 ppm
WHO indoor air guideline: 0.08 ppm (80 ppb) for 30 minutes (chosen to prevent sensory irritation and cancer risk)
EPA reference concentration: about 7 micrograms per cubic meter (roughly 5.6 ppb) for chronic inhalation
California CARB Phase 2 emission standards limit formaldehyde from composite wood products sold in the state, adopted federally by EPA TSCA Title VI

What you can do

Choose furniture, cabinets, and flooring labeled CARB Phase 2 compliant, TSCA Title VI compliant, NAF (no added formaldehyde), or ULEF. Solid wood, metal, and glass do not off-gas formaldehyde.

Ventilate when bringing new pressed-wood items home. Open windows, run bath and kitchen exhaust fans, and use mechanical ventilation if your home is tight. Air new items in a garage or unused room for several weeks before moving them into bedrooms.

Do not smoke indoors. Vent gas stoves with an exhaust fan during cooking. Avoid unvented combustion heaters. Plain HEPA filters do not capture formaldehyde because it is a gas; specialized filters with activated carbon, potassium permanganate, or similar media remove it chemically.

Sources

This article is for educational purposes only. Canairy does not provide medical advice, diagnosis, or treatment. Talk to a qualified health professional about your specific situation.