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Published in Summer 2001
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Air pollution contributing to respiratory problems
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Over the past 15 years, asthma has reached epidemic proportions in large areas of North America, children being particularly severely affected by the disease. When the Commission's Council adopted a resolution on Children’s Health and the Environment in June 2000, asthma was first among the health issues chosen as a starting point for cooperation between the partners. In the first of our pair of articles, Michael D. Lebowitz explains why children are particularly susceptible to asthma and notes the spread of the disease among disadvantaged children. In the second, Irma Rosas discusses the situation of children in the highly polluted environment of Mexico City, and points to the complex interactions between pollutants suspected of causing asthma.
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By Irma Rosas
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Read related article: Asthma increasingly affecting North American children
In Mexico City children under 14 make up close to half the population of approximately 20 million. What are the effects on them of the city’s highly polluted air (with concentrations of ozone and fine particles frequently far in excess of levels considered acceptable for health)?
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| Asthma causes breathing difficulties that may necessitate supplemental oxygen. |
In general, the effects can be seen in irritated, inflamed respiratory tracts, with reversible deterioration in lung function. While specialists put the incidence of asthma in children at between 5 and 10 percent, and say that the situation does not appear to have worsened in recent years, reports from hospital emergency services indicate they are treating more cases of aggravated asthma that require a longer hospital stay.
Managing an illness such as asthma, which has multiple causes, can prove more complex in a developing country. For example, malnutrition seriously affects children's health, making it more complex to identify the role of other factors, including the environment.
Childhood asthma is seasonal, showing patterns similar to those observed in adults under the age of 60. The number of cases reported peaks between July and September, which is the period of heavy rainfall characteristic of tropical countries such as Mexico. The rains cause a decrease in common air pollutants such as ozone, which suggests that other types of pollutants found indoors and outdoors, such as allergens and biogenic compounds, may be the primary factors responsible for provoking asthma, and that they are interacting in some way with other pollutants.
Because allergy-type asthma is very common among children, the daily monitoring of allergens (such as pollen, spores, algae) carried out in various parts of the world is very useful in controlling the illness. In Mexico, unfortunately, we do not have access to this type of information. However, the few specific measurements that have been taken indicate that it is vital to implement such monitoring.
Another factor to be considered is that in developing countries the lack of planning combined with rapid growth rates render public services such as sewer systems inadequate, leaving people with no option but to defecate directly onto the ground. Dried feces become a source of airborne particles that are high in bacteria and bacterial products. Samples of airborne particles have shown the presence of compounds from the external membrane of bacteria which have a high potential for provoking inflammation (specifically, endotoxins).
It has also been documented that in highly polluted cities, pollen grains and some of their components interact with smaller particles, increasing the chance of human inhalation. All this demonstrates that pollutants from vehicles and industries, as well as those of biological origin, must be considered as major factors which, alone or in conjunction with others, have a significant effect on illnesses such as asthma.
Children who live in tropical countries spend much more time outside than children who live at latitudes farther from the equator—first, because they spend less time in school, and second, because the climate permits it. Epidemiological studies conducted in Mexico seeking to establish the association between pollution and increases in morbidity and mortality in children have thus far looked only at outdoor exposure. In the case of asthma, however, I believe that the study of both types of environments would lead to a truer assessment of exposure to pollutants, and would allow more effective proposals for controlling this problem to be formulated.
I am greatly encouraged by the Commission’s proposal to convene an Expert Advisory Board to provide advice to the Council on key issues of children’s health: this is a great opportunity for North America and especially for Mexico. Aspects relating to asthma that should be covered include: environmental regulations; identification of the compounds that should be monitored in the environment; and the epidemiological use of more specific indicators and "bio-markers" that could be borrowed from molecular epidemiology and toxicity studies in vivo and in vitro.
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