Proposed residential indoor air quality guidelines for formaldehyde

Abstract

In the 1980s, Health Canada and the Federal-Provincial Advisory Committee on Occupational and Environmental Health (CEOH) developed a series of indoor air quality guidelines that were published in 1987 in a report entitled Exposure Guidelines for Residential Indoor Air Quality (CEOH 1989). For formaldehyde, target and action levels were set at 60 μg/m³ (50 ppb) and 120 μg/m³ (100 ppb), respectively. However, since then, a significant amount of research has been carried out and published on the health effects of some of these substances, warranting a reassessment of the scientific basis of the guidelines and potentially a revision of the guidelines themselves. The purpose of this document is to revisit the guidelines developed for formaldehyde in view of epidemiological and toxicological studies published since 1987.

Based on human clinical studies and on animal experiments, the primary effects of acute exposure to formaldehyde are the irritation of the mucosa of the upper respiratory tract and the eyes. The no observable adverse effects level (NOAEL) and lowest observable adverse effects level (LOAEL) for this outcome are 615 and 1,230 μg/m³ , respectively.

Epidemiological studies on the effects of chronic formaldehyde exposure consistently found respiratory and allergic effects at levels below 123 μg/m³ . In one study, formaldehyde levels in homes were associated with increased risk of atopy, after ruling out confounding from other indoor air pollutants. In another study, formaldehyde levels were significantly associated with hospitalization for asthma in children aged six months to three years, again after ruling out confounding from other indoor air pollutants. No effects were found in children exposed to 10 to 29 μg/m³ and 30 to 49 μg/m³ formaldehyde, a non-significant increase of risk was observed at 50 to 59 μg/m³ and a significantly increased risk was observed at 60≥μg/m³ . An association between low-level exposure to formaldehyde and the development of allergic sensitization and/or asthma is biologically plausible as it is consistent with observations in animals.

There is evidence from toxicological and epidemiological studies that inhaled formaldehyde is carcinogenic. However, formaldehyde-induced carcinogenicity appears to be a consequence of proliferative regeneration following cytotoxicity, and the risk of cancer associated with formaldehyde levels sufficiently low to prevent irritation and inflammatory responses appears therefore to be negligible.

The following guidelines are therefore proposed for formaldehyde:

• a guideline for short-term (1-hour averaged) exposure at 123 μg/m³ (100 ppb); and
• a guideline for long-term (8-hours averaged) at 50 μg/m³ (40 ppb).