Air Fresheners Create Indoor Smog
UPdate spring 2005

Plug in air fresheners containing fragrances such as pinene and d’limonene can combine with ozone in the air to create a potentially harmful smog inside houses. Ozone is a common component of both urban and rural air. Researchers from the US Environmental Protection Agency (EPA) studied what happened when the substances combined as they would in an indoor environment.  They found that the combination generated formaldehyde, a probable carcinogen, as well as related compounds which are associated with respiratory problems.

Mixing ozone with air freshening chemicals resulted in formaldehyde-related compounds at a concentration of about 50 micrograms per cubic meter of air. This is about the same concentration as a freshly painted room. Other substances in the home would raise particle levels to a higher level. The EPA’s standard for good air quality is a concentration of 50 or less.  People who use ozone generators in their homes as well as air fresheners would be exposed to significantly higher levels of contaminants.  

"If you are concerned about indoor air, you should not introduce any extra chemical sources to your home, and that includes volatile organic compounds and ozone," advises Frank Princiotta, director of the EPA's Air Pollution Prevention and Control division.

“We do not think that 'freshening' air is a good way to deal with air pollution," says Ken Giles, public information officer at the US Consumer Product Safety Commission, which regulates products such as air-fresheners. It is better to prevent the smells you are trying to disguise in the first place, rather than covering them up with more chemicals, he explains. 

Ken Donaldson, a toxicologist at Edinburgh University in the UK notes, “Basically, this is yet more particle exposure, which you do not want."  According to Donaldson, the particles created in the study are similar to those emitted by vehicle exhausts, which are known to cause respiratory problems.  An increase of ten micrograms of particles per cubic metre of air is estimated to lead to a 1% increase in deaths from conditions such as asthma.

The researchers did not comment as to whether other products which contain the same fragrance chemicals would create similar toxic mixtures. These chemicals are common in fabric softeners, laundry detergents, cleaners, and numbers of other products.  

Editor's Note:
To find less toxic ways to freshen air, consult