Seasonal variations in death rates for young children are related to high levels of particulate air pollution and cold temperatures during the winter months, and to high levels of particulate pollutants and nitrogen dioxide during the summer months, according to a Spanish study in the August Journal of Occupational and Environmental Medicine, official publication of the American College of Occupational and Environmental Medicine.
Led by Dr. J. Díaz of Universidad Autónomo de Madrid, the researchers reviewed weather and pollution monitoring data for Madrid from 1986 through 1997. They sought to determine how these environmental factors affect death rates among children less than 10 years old.
The results showed significant interactions between daily temperatures and levels of specific air pollutants. In the wintertime, child mortality rates rose a few days after cold days with high levels of particulate air pollutants ("total suspended particles," or TSP). Death rates increased dramatically after cold days with temperatures less than 43° Fahrenheit (6° Celsius).
In the summertime, child mortality rates rose also along with TSP levels, as well as with levels of nitrogen oxide pollutants. Most of the temperature- and pollution-related increases in death rates were limited to children between 1 and 5 years old.
The effects of temperature and pollution in children differed from those in adults, based on previous studies from Madrid. For adults, death rates increased on both the warmest and coldest days, whereas temperature-related risks in children were limited to cold days.
In contrast, the effects of pollution were greater in children. Child mortality rates were especially high on days with TSP levels of more than 100 micrograms per square meter, which occur mostly during the winter. Children's airways are narrower, meaning that they are exposed to a higher concentration of pollutants with each breath. Children are also more likely to be outdoors and physically active on warm summer days when pollutant levels are high.