The “fresh air” smell of a lot of air fresheners is really the smell of pollution according to a paper from scientists at the National Institute of Environmental Health Sciences. That’s because 1,4 dichlorobenzene (1,4 DCB), found in air fresheners, toilet bowl cleaners, mothballs and various “deodorizing” products, also causes modest decreases in lung function.
“Even a small reduction in lung function may indicate some harm to the lungs,” said NIEHS researcher Stephanie London, M.D., lead investigator on the study. “The best way to protect yourself, especially children who may have asthma or other respiratory illnesses, is to reduce the use of products and materials that contain these compounds.”
The researchers examined the relationship between blood concentrations of 11 common volatile organic compounds and lung function measures in a representative sample of 953 adults. VOCs are a diverse set of compounds emitted as gases from thousands of commonly used products, including tobacco smoke, pesticides, paints, and cleaning products. VOCs are also released through automotive exhaust. The researchers found that of the common VOCs analyzed, which included benzene, styrene, toluene, and acetone, only the compound 1,4 DCB was associated with reduced pulmonary function and this effect was seen even after careful adjustment for smoking, The researchers found that 96 percent of the population samples had detectable 1,4 DCB blood concentration levels. African Americans had the highest exposure levels and non-Hispanic whites the lowest. (via Science Blog)
This is another example of indoor air pollution from a consumer product. The reductions in the particular measure of pulmonary function, Forced Expiratory Volume in 1 second, compared those with the highest body burdens of 1, 4 DCB and those with the lowest. The differences were fairly small, about 4%. Concurrent risks that might have confounded the association were accounted for, including type of heating, use of wood fires, age of house, presence of furred pets, occupation, socioeconomic status, environmental tobacco smoke, smoking history, and diagnosis of asthma or emphysema.
FEV1 is an indicator of relative airway obstruction. One might ask if a 4% decrease, even if statistically significant is of public health significance. The answer is yes, for two reasons. The first is the one indicated by London. It is an indication there is damage to the lungs.
The other is more subtle. Pulmonary function tests give measurements of lung function that are vary in the population in a continuous distribution. Everyone has a substantial reserve in pulmonary capacity and we don’t see clinical symptoms until a substantial amount of pulmonary function has eroded. At some point we move from someone without symptoms to someone who begins to have clinical effects. If you imagine a big bell curve of FEV1 measures, at some point in the lower tail of that curve where some people begin to get short of breath. Many things will determine your position on the curve, not just whether you have air fresheners in your home. But if you take the whole curve and you move it to the left by a 4% decrement in FEV1, you start to push some over the line separating asymptomatic and symptomatic. Because the area in the tail of the distribution is fairly small compared to the area under the rest of the curve, a small leftward shift can cause a substantial increase in the percentage of people with clinically evident obstructive pulmonary disease.
If this worries you, that’s appropriate but don’t panic. Stop, collect yourself and take a deep breath. Oops!