Study Shows Metals in Air Aggravate Asthma and Allergies
Microscopic pieces of metals in air pollution aggravate asthma and allergies, according to research by the U.S. Environmental Protection Agency and German scientists published this week.
The researchers concluded that people who live in areas with airborne soot that contains a lot of metals are prone to more severe bouts of asthma and allergic symptoms.
Evidence has been mounting in recent years that soot -- ultra-fine particles of pollution -- aggravates asthma and allergies. The new study implicates a specific ingredient of the soot -- metals, such as zinc, copper, tin and cadmium. The metals are most often found in emissions from factories and coal-burning plants.
Asthma is considered an epidemic in the U.S., afflicting an estimated 15 million people, including 5 million children.
For their study, EPA and German scientists examined air from two neighboring cities in East Germany, Hettstedt and Zerbst. Hettstedt, which has a high rate of bronchitis, allergies and wheezing among schoolchildren, is home to smelters and mines. It has several times more toxic metals in the air than the nonindustrial, farming area of Zerbst.
When lab mice with allergies were exposed to airborne particles from Hettstedt, they had more inflammation of their airways and worsened allergic symptoms than animals exposed to particles from Zerbst, according to the research, directed by Stephen Gavett of the EPA's National Health and Environmental Effects Research Laboratory in North Carolina. Although the concentration of particle pollution was similar in both cities, the content of some metals in Hettstedt was as much as sevenfold higher.
Apparently, tiny pieces of metals cause airways to become inflamed, restricting the flow of air that reaches the lungs. Such symptoms can lead to asthma attacks. The metals also increased the animals' sensitivity to common allergens -- substances such as dust or pollen that cause allergic symptoms.
There was no evidence, however, that soot causes the diseases in people who don't already suffer them. When mice that were not allergic were exposed, they had no symptoms. Instead, the metals exacerbated symptoms in mice with existing allergies.
Gavett concluded that timing is critical to determine how severe someone's symptoms will be. When mice breathed the metals right before being exposed to an allergen, their airway inflammation worsened.
