UC DAVIS (US) — Exposure to nitrogen oxides in air pollution may increase acute bronchitis episodes in young children, a new international study shows.
The association increases with age in the first two years—in other words, children between the ages of 1 and 2 show a stronger association to those below 1 year. A similar trend was not evident in children between the ages of 2 and 4 1/2 years, says lead author Rakesh Ghosh, a postdoctoral researcher in the department of public health sciences at the University of California, Davis.
“Acute bronchitis is relatively common in preschool children,” says Irva Hertz-Picciotto, professor and chief of environmental and occupational health and principal investigator of the study published online in Environmental International. “We found an exposure of approximately 35 micrograms per cubic meter of nitrogen oxides increased incidence of acute bronchitis by about 30 percent.”
Acute bronchitis involves inflammation of the main airways to the lungs and often occurs after a viral infection. It causes cough, fatigue, and low-grade fever, and may be followed by several weeks of a dry, nagging cough. About 20 percent of deaths in children younger than 5 years are due to acute lower-respiratory illness.
Nitrogen dioxide is known to be a deep lung irritant and is regulated by the U.S. Environmental Protection Agency (EPA). The standard is no more than 188 micrograms per cubic meter for any one-hour average and no more than 100 micrograms per cubic meter as an annual average.
The study was conducted in two districts in the Czech Republic: Teplice, and Prachatice, where ambient levels of nitrogen oxides were regularly monitored. The mixture of gases, consisting mainly of nitrogen dioxide and nitric oxide, are pollutants that result from burning fossil fuels in industrial installations such as power plants and automobiles.
For the study, researchers monitored daily ambient nitrogen-oxide levels starting in May 1994 through June 2003. A total of 1,133 children were followed from birth up to 4 1/2 years of age. The children’s respiratory health information was obtained from medical records and additional information was collected using maternal questionnaires.
The researchers also examined what fuels were used in the children’s homes for heating and cooking, i.e. gas, electricity, or coal, and other potential exposures, such as second-hand cigarette smoke. The increased association found solely from air pollution persisted even after accounting for these other factors.
“Although our results are not directly comparable, because the current regulatory standards are for nitrogen dioxide and we investigated a mix of nitrogen oxides, the standards are much higher than the levels associated with increased incidence of respiratory illnesses in this study. This means that levels considered safe actually may pose a risk of elevated rates of respiratory disease in young children,” Hertz-Picciotto says.
Researchers from the Institute of Hygiene in Teplice, Czech Republic and the Institute of Experimental Medicine, Academy of Sciences, the Czech Republic in Prague contributed to the study that was funded by the Czech Ministry of the Environment.
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