Asthma is a chronic inflammatory disease of the airways. It is estimated by the Centers for Disease Control and Prevention (CDC) to affect about 8.5 percent of the total U.S. population and 9.2 percent of children under the age of 15 (as of 2012). Incidence of childhood asthma more than doubled in the United States between 1980 and the mid-1990s, according to CDC, but has leveled off since then. Much of the increase was seen in African-Americans, particularly children.
No one knows for sure what causes asthma. Although allergies play a role in many people with asthma, it is not true in all cases. As with allergies, there is a strong genetic component for asthma.
A large majority of people with asthma have allergies to airborne substances such as tree, grass, weed pollens, mold, animal dander, dust mites, and cockroach particles. Such allergens can act as triggers for asthmatic attacks. The U.S. Environmental Protection Agency advises that the most common indoor asthma triggers include secondhand tobacco smoke, dust mites, molds, cockroaches and other pests, household pets, and combustion byproducts. Although it has been suggested that phthalates can act as asthma triggers, extensive testing has not shown phthalates to be allergens, nor has research shown them to be strong irritants. As a consequence, it is unlikely that phthalate exposure could act as a trigger for asthmatic attacks.
Furthermore, phthalates do not easily migrate out of flexible vinyl products because they have very low volatility and are tightly bound in the molecular matrix of flexible vinyl. The range of airborne concentrations of phthalates in a room with vinyl floor and wall coverings, for instance, has been measured to be extremely low (ranging from undetectable to just a few millionths of a gram per cubic meter of air). In inhalation studies on rodents, concentrations more than a million times greater than ambient levels have been required to result in an irritation reaction in rodents, further indicating that it is unlikely that inhalation of phthalates could be an asthma trigger in humans.
It also has been suggested that tiny polyvinyl chloride (PVC) fragments containing phthalates that are released by the normal wear and tear on vinyl surfaces can contribute to potential irritation caused by household dust. Such releases are slight, however, even over a period of years. Moreover, vinyl particles make up just a small fraction of household dust, which typically contains dust mites, dead skin, molds, surface soils and many other allergy-inducing components.
The Institute of Medicine (IOM), an arm of the National Academy of Sciences, also evaluated possible asthma causes and triggers. A report published in 2000 titled “Clearing the Air: Asthma and Indoor Air Exposures,” stated that there is “inadequate or insufficient information” to support the idea that phthalates and other plasticizers present a problem for asthma sufferers.
Research on Phthalates
In research published in 2003, various phthalates that were applied on the skin of mice did not produce the specific marker proteins that are associated with allergic illness. Because the tested phthalates did not show the types of immune responses associated with respiratory allergy, they are unlikely to induce asthma by an allergic response.
A study published in 2004, by a team including Danish researcher Gunner Nielsen, concluded that, “Based on a worst case scenario in the general population, no airway irritation is expected from non-occupational levels of MEHP originating from DEHP.” Other research submitted to the Society of Toxicology in 2005 reported that DEHP painted on the skin of rats already sensitized with a known allergen did not magnify the allergic effect. In 2009, work published by Dearman concluded that “the doses of (BBP—used in vinyl flooring) encountered in the home environment are unlikely to be a major factor contributing to the increased incidence of asthma and allergy in the developed world.”
Research conducted in Germany and published in 2004, by Becker et al., compared the levels of the phthalate DEHP in household dust to the level of metabolites of DEHP in 254 children. The purpose was to see whether higher concentrations of DEHP in the dust corresponded with higher exposure levels in the children, which might add support to the hypothesis that phthalates in dust could contribute to the induction of childhood asthma. The study’s authors reported that no correlation could be found between DEHP levels in dust and metabolite levels in the children, which casts additional doubt on the possible contribution to incidence of childhood asthma. Another assessment reported that the potential human exposure levels from phthalates in dust is between 100,000 and 1,000,000 times lower than levels in rodents that produced minimal effects indicative of respiratory inflammation.
Based on these studies, it is believed that phthalates do not cause, and are not likely to exacerbate, asthma.
You can learn more about asthma and indoor air quality from EPA's website: An Introduction to Indoor Air Quality (IAQ).