Air particles raise risk of childhood asthma

By: Barbara Ha

Posted: 2/26/09

It is widely believed that poor air quality can trigger an asthma attack in those who already have the illness. New evidence from scientists at the School of Medicine and Bloomberg School of Public Health suggests that problems with indoor air quality can cause serious respiratory problems in asthmatic children.

The report, which appears in the February issue of Environmental Health Perspectives, is the culmination of a six-month study of young children. The researchers, led by Meredith McCormack of the medical school, found that increased levels of particulate matter in the air of children's homes causes increased asthma-like symptoms, as well as an increased use of medications, like albuterol inhalers, that protect the airway.

From these results, the scientists conclude that reducing indoor particulate levels may lead to a decrease in the incidence of asthma, especially among children living in inner city areas such as Baltimore. Asthma levels have been steadily increasing over the last several decades.

Particulate matter refers to the fine particles that are suspended in the air we breathe. It can include dust, car exhaust, chemicals released while cooking and cleaning, smoke, pollen and fungal spores, among others. Many of the particles in air are filtered in the nose and lungs without causing harmful effects, but some types of particles can cause various adverse effects throughout the respiratory system - the nose and mouth, throat and lungs.

The researchers, who are all affiliated with the Hopkins-based Center for Childhood Asthma in the Urban Environment, selected 150 young children with asthma. The children, who were all from Baltimore and were mostly black, were in the age range of two to six years.

The team assessed the amount of particulate matter in the children's bedrooms over three-day intervals. Their caregivers were asked to complete questionnaires every day, in which they were asked questions about the children's health.

Particulate matter is classified based on its source and its size. A great deal is already known about outdoor particulate matter - pollen, for instance - which has already been shown to dramatically increase the risk of an asthma attack and other respiratory complications for asthmatic individuals.

Unfortunately, even though most people spend much of their day indoors, much less is known about indoor particulate matter. The concentration of many kinds of particulate matter is much greater indoors.

It is known that the smaller, fine indoor particulate matter affects the alveoli, sac-like areas of the lungs where oxygen and other gases are transferred into or out of the blood. Coarse particulate matter can build up in the linings of the airway and can cause irritation and other symptoms - including asthma attacks, in which the airways suddenly tighten.

Asthma is particularly common in people who live in cities in the United States. The disparity in asthma occurrence is related to many factors, including access to medical care, exposure to other children during early childhood, diet and stress.

Many recent studies have caused researchers to speculate that exposure to environmental pollutants may play a crucial role in the development of children's respiratory systems.

Many barriers remain to better air quality. These researchers hope to add to the body of knowledge that suggests that poor indoor air quality can cause just as much harm as poor outdoor air, contrary to what many national guidelines would suggest.